I have been repairing home/professional audio equipment for 15 years as a hobby. I have learned the power of schematics. Just wondering for those that repair mobile audio equipment how does one start to diagnosis without a schematic? Are there any universal schematics since alot of mobile power amps are similar. I purchased a new used Dual XPR522 and it has operated well for months. Now there is an intermittent static noise on the right channel. Removed amp and put it on the bench and powered it up with speakers and confirmed it is the amp. Monitored DC offset on right channel and at power up 15mV after several minutes it increases to 150/200mV. Took it out of the aluminum shell and have it bare board on the bench. Nothing smoked or discolored. Wanted to inspect solder connections and traces......suspicious of a bad solder joint.
Being one channel it is not power supply related. Most likely something in the amplifier stages.
The intermittent static noise is not affected by volume.
and I already know that this amp is probably considered a throw away but I am one of those individuals that cant bring themselves to throw away a piece of electrical equipment that possibly just has a bad solder connection.

Hey!
What are experiences with speakers from Lii Audio?
Which ones have you tried?
Is anyone impressed?
Regards

Used Hitachi 2SK227 (K227) Silicon N-channel Mosfet. See picture from datasheet for more details. The mosfets were taken from a Rausch DVT PA-ampflifier. The 2SJ83 is the
counterpart to the chip. I have not tested the mosfets but they seem to be in good shape. These mosfets are very hard to find!


$8 each plus $5 in shipping world wide (Each Additional Item +$1)

5 AVAILABLE

To whom It may concern,

Anybody who knows where I can have this MAS Solitaire MK-1 schematic diagram?

Thanks,

John

hello,

I picked up a really nice PYE TEN mono amplifier. i was getting a weak intermittent signal and found the track to one of the power transistors was broken so i repaired this and have a bit of the normal healthly low level buzz to show the amp is ready to output sound.

Problem is I think the previous owner may hay messed with the volume tone wiring and possibly rewired it wrong from the rough soldering and it appears to be missing a purple wire from 'F' and only has a film cap. i cant make the wiring how it should be.

the pots from left to right are....
selector (input orange + blue)
volume 25k then tone 25k.

if any one has worked on these or similar model and knows the pin lettering or can identify how the tone/ volume pot wiring should be that would be great to get it working again. thanks

update i disconected the pots from the pins and have ran an audio signal through to pins B/A.
have used a blue tooth speaker to ground try extract audio from the other pins.

pin D i got motor boating
pin E motor boating plus very rough audio signal
pin C acceptable slightly clipped audio signal

I have managed to get some scratching from the test speaker by rubbing pin F to Chassis. Have tried inserting an audio signal to pin F but there is no output to speaker.

I think it may have bigger problems so may just use the chassis for a project.

Hi, im here again with my amp and now i designed pcb and i would be very glad if you can me tell if its good or if i can somehow improve my design.
Everything is in attachments. If you need something more i can add it. Thank you very much for your help guys 😉

hi there anyone got a schmatic for the "marshall origin 20" model or120c.

I have not plugged it in yet but am told it goes ok for a couple of minutes the just fades out.

schmatic would be good or if anyone has experience with this model and has ideas as to cause of fault please chime in.

all rdy noticed that the output trany is connected to circuit board with spade connectors which are quite lose, but i don't think that's the problem

Just seems like the most eloquent solution to directing the correct frequencies to the correct amplifiers without additional external wires and separate power supplies. I have Wayne's line stage board and the NP x-over board. Any interest in the community to merge these schematics? Peace

Hi all,
Can I connect the grounds of these two supplies, is this OK? I have popped the snubber cap on the negative rail (47u) and the regulator is kaput. I'm not sure if the cap was connected in reverse but, I replaced the regulator and cap and also disconnected the indicated ground and it's all good. Was it the cap or the grounding I'm not sure. I'm also not happy that this 338 burns with a reverse cap, if thats the case... (24V adjusted output give 35 after the pop and cap replacement... source is 40)

I'd like to share my experience with Beezar audio (beezar.com) as I couldn't find a section dedicated to web shop review.

Beezer Audio is an awesome shop.

Prompt shipping, fantastic online-documentation and AMAZING after-sales from the owner (Thomas).
Highly recommend this shop, plus you support a sole proprietor!

I bought two DAC's and two high quaintly USB power supplies, both a DIY solder kit.
As both kits require some advance soldering (I am a novice) I wanted some additional information before the purchase contacted the store with some questions over the 4th of July weekend.
Within a hour I got a detailed response back from the owner. Which was excellent.

Both kits have very detailed website, with amazing instructions and photos, which were a great help and the level of detail is truly amazing:
http://www.diyforums.org/PupDAC/PupDACoverview.php
http://www.diyforums.org/Doodlebug/DoodleBugoverview.php

Shipment was quick and without any issues.

As I am new to SMD soldering I broke two tiny components.
Luckily the kits come with a bill of material (see websites) including Mouser and Digikey part ID's
Yet due to supply chain issues the required replacement are back-ordered for >12 months.

I contact Thomas on advise on alternative components I found and whether these would work.
He confirmed the alternatives would work, but offered to ship the needed replacement parts (he had on spare) for free!
These are components I broke and he did not needed to replace these at all, yet he did for free!

Since then we exchanged emails a few times about the build process and he's been very supportive and patience.
Awesome!

So, overall excellent service, great communication and thanks to the on-line documentation I greatly improved my soldering skills.

p.s. Im not affiliated with Beezar Audio in any way nor paid to write a review. Just a happy customer.

I have tried a few searches on the site but can find no threads on single MOSFet Class A amps with inductive loading. Has anyone successfully done this and can tell me about it and what they did? Any schematics? Should this continue as a new thread?

I have built my own single MOSfet amp with resistive loading but understand inductive in the source leg can be achieved.

Please find photos of the above. Does anyone have the original article?

Hi there

I revisited the laser etching method used by some for PCB's using it for aluminium laminated foil is a bit harder though 🙁

Part1 - Test ! piece
Login to view embedded media Part2 - Actual size test foil
Login to view embedded media Part3 - Reason why i am not going to use a foil like this for my current build
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Assembled and tested 3-phase sine wave generator and output board, dialed-in for the BLWS motor suggested in the thread.

$150 shipped USPS Priority in the US.

https://www.diyaudio.com/forums/ana...sinewave-generator-turntable-motor-drive.html

https://www.diyaudio.com/forums/analogue-source/307918-3-phase-class-amp-diy-bldc-motor-drive.html

Hello good people of the internet!

The short version is: I want to transform my Sony WH-1000XM4 into an aviation headset
This is nothing new, I've seen plenty examples of people building aviation headsets from consumer headsets. There are even companies (I know of 4) whose sole business is selling these adapters (for $200-$300, which seems a bit steep). On diyAudio, I read this topic and that topic but they don't answer all of my concerns. I know very little about audio but I'm handy enough with a soldering iron and 3D printer.


What I understand:

• the aviation panel expects a load (is it called a load?) around 300-600Ω
  • I measured the resistance (with a multimeter in DC, I don't have a function generator, nor would I know how to measure an impedance with one anyway) of my cheap headset between 130Ω et 1300Ω (there is a potentiometer that makes the value change)
• Sony says the WH-1000XM4's impedance is 16Ω when turned off (but wired) or 40Ω when turned on (still wired). I will use them turned on 99.99% of the time since the goal is to have active noise reduction.
  • This article says around 17.6Ω average, I guess it was with the headphones turned off
  • I measured the resistance (still with my multimeter) of the WH-1000XM4 at around 50Ω (turned on or off. This isn't surprising since the article above showe impedance is way above 16Ω at low frequency)
• Some people use an impedance matching transformer in their designs, some people say a potentiometer is enough

What's a bit hazy: If I go from the mono audio signal of the panel to my stereo headphones, will I need to wire L&R in parrallel? Will that divide my impedance by two?

I don't want to damage the aircraft's equipment, nor my fancy headset...so, should I use an impedance matching transformer? If it's not 100% necessary, what's the drawback of not having one?
How to choose it? Does it need to be specifically, say 300:20 or can I use any transformer that has a ratio around 10:1?

Should I include a potentiometer?


Thanks for your future answers

So, just a quick post to share a successful repair I just did to a Philips CD150 which I got for almost nothing, with the indication that it wouldn't read any CDs (showing Err). This turned out to be a hard one to diagnose and in the process I learned and discovered a lot about philips cdm transports and this player in particular, so I think this can be very useful for some people, although the player itself was kind of low-end at the time, it still sounds quite nice. If it was one of the better ones (let's say, TDA1541 at least), I'd now start modding it as I did with my Marantz, but like this, I'm simply going to sell it cheap. This was more for learning than anything else.

Here we go:
first things first - I opened it and cleaned the lens. Nothing improved.
I then took my mobile phone camera and "made a movie" of the laser lens when hitting play. It showed that nice tiny red dot and also the coil moving up and down, so laser and focus was working. Decided to clean inner lens (which is quite easy with the CDM laser head). No improvement.
Next, I searched the internet for the service manual (first I didn't get the manual for the CDM, only for the player). Found out about the three service positions. Tried them out and the player clearly passed stage 1 and 2, but then, the number 3 would sometimes appear very shortly but it would immediately stop and go back to 0. Sometimes even with the swing arm making a hard stop against the limit.
I tried the Fast forward and Backwards keys to move the swing arm, responded well, although sometimes would engage in a strange kind of "stutter", I mean, it seemed to get stuck, vibrating. Very odd.

I starting measuring, laser voltage seemed ok, although it would vary a lot, depending on the actual position/state, but I guess that's normal.
Measured all supply voltages and got kind of confused - it didn't measure +-9V, but +12 and -13V, which is very high for CDM, I think. So I (mistakenly, as I discovered later) thought there could be a problem with the power supply (transformer hums audibly), checked all, even changed the supply wiring to 240V (was 220V), didn't make a change, then I even built a little regulator circuit with LM317 and 337 to feed clean +9,5 and -9,5V to player, which turned out to be a waste of time - player behaved exactly the same way and the regulators would get hot, would need large heatsink, so I ditched this idea.

Next and after searching and reading a lot on the internet, I decided I would recap the servo board, as frequently the electrolytic caps have dried out, especially those blue Philips axial, the infamous C2103 especially. So I did this but nothing improved. Then, when I was trying to measure some stuff (was starting to think that the problem would be in the radial drive, for example the driver IC), while suddenly the player advanced to service position 3!! 😕 I was confused and surprised and immediatly decided to try it out to play a CD, connected to my amp, and well, it played! Music sounded good. But it stopped after 1 minute and didn't play again...

So, now I knew that the laser and transport should be fine, as well as the DAC and general control circuitry, although it still could be the radial drive or something, which caused it to loose tracking or not play at all.

I got myself the service manual of CDM-2, but then actually found out that this player had received a new laser head, the CDM-4, somewhere in the past, as the servo board was CDM-2/29, if I'm not mistaken right now, but the laser is CDM-4. This was interesting and I actually found the part where Philips indicates exactly what has to be modified to be able to make the CDM4 laser work with the old servo board. I checked all of the adaptations, I mean, I didn't know the history of this player, maybe adaptation was made wrongly? But no, all was exactly as in service manual.

I was getting a bit desperate and was running out of ideas. But then I had an idea: what if the player would need to warm up to be able to play? As I had it on when I was measuring for quite some time! Well, I left it on half an hour. And guess what? It worked! Not perfectly, but would play here and there.

I then searched the internet for this and found the solution: it appears that Philips at that time used so called "griplets", which seem to be a very frequent problem on more well known players like CD104, for example, and can cause all sort of problems which generally go away when player is warm. What seems to happen is that the solder in those griplets (which connect one plane of the PCB to the other) has cracks and doesn't conduct well anymore, while with heat and thermic expansion, it starts to conduct better.
So I decided to take care of the main decoder board, as it was the only PCB with griplets and in the process also recap most of the electrolytics.
I didn't drill the griplets, as they recommend for CD104, as here each and every of them leads directly to ground plane and some have one leg of a capacitor in it, so I simply sucked out the old solder with desoldering pump and scratched a bit of the copper on the top layer to get the oxidation off and then put quite a lot of solder to reflow the whole griplet and solder to the scratched place to make sure it had good connection to top ground plane.

After all this, I tried it out (cold, obviously) and bingo!! Worked!!! 😀😀
I took the opportunity to verify laser voltage adjustment, which was perfect and made some other measurements, all checked out fine.
Problem solved! I tried it out with several different CDs, some pressed and also quite a few CD-R, it reads all of them, although it takes quite some time to read the TOC of a CD-R, which doesn't happen with pressed CDs, there it's very quick. Takes some 20 seconds to read TOC of some CD-Rs. But then plays them flawlessly, no skipping, and goes to all tracks, even 80 minutes CD. So I guess that's normal.

While testing, I also found another problem by mere chance (and am glad that I did!), one of the connectors to the display board was too loose, I tried contact spray and whatever, but it would loose contact when I'd touch the wires and scramble display and make controls not working. I decided to go the radical route - I just cut the wires and soldered them directly to the board. Problem fixed.

Ah, before I finish: I upgraded the power supply caps while recapping, put some much bigger ones. And I had to make the tray working again, with a new belt (not original, but works), but that strange door was causing problems (why did Philips make a door? had never seen this!), decided that the spring was too tight, so I simply cut a few of the windings of the spring so that door would stay shut but open much easier. Problem solved!

So, I now have a fully functional CD150 for sale, I'm listening to it as I'm writing this, sounds nice. Learned a lot with this one.

Ah, and last but not least: as I didn't have access to original Philips BC capacitors, which apparently are the best for that (in)famous C2103, I decided to install a 47uF capacitor of a not very well known and certainly not expensive brand. As I had read that it shouldn't have low ESR and that a bit more of capacity actually could be good. And well, it works perfectly, AFAIK, no reading or tracking problems and laser voltage stays precisely at 49,8 mV. Was I just lucky? Or is this capacitor not so critical in some of the players or, just an idea, if they are upgraded with CDM-4 on old servo board, as this one?

A couple of photos after cleaning, recap and player working fine (didn't take at details):

Hi, long time no see!

recently i got from a friend a good old amplifier from rockford fosgate. Its the P8004 4 channel amplifier, which stated in its name.

Amplifier was working ok but suddendly stopped working from one of their 4 channels. Short yellow led lit, so we removed from the car and bench test it.

None of the 3 40 amp fuses blew, and the amp still worked on the 3 remaining channels, good clear sound, no distortion.

Front left channel blew (a low pitch tone), so i discovered my friend wired in paralell an infinity kappa speaker , 2 ohm, with another focal 6 inch speaker, 4 ohm, so, yikes! Thats 1.3 ohm so way low from the 2 ohm stereo per channel spec!

Well, i went to test all the transistors, so the first row of two 28n15 were bridged to ground, got 0 ohms each way. The another ones (fqa36p15) werent shorted, and tested all the transistor, and they at least were not shorted.

So i ordered a pair of 28n15, installed them on the MEHSA strip (god, that was not easy!), and discovered two of the small condensors on C117 and C118 blew in half. Weird! I said, maybe i damaged them without noticing.

I searched on the net, and found schematic of the amp, so , if my memory serves me right, the replacement part i need its a “ 104- condensador de 0.1 microfaradios, 50 Volts, 5% tolerancia”. That being said, i jumped to my nearest electronic parts supply, but found a part with +80% -20% tolerance range! So i am stumped if i can use this part, or if i need the exact replacement.

i am attaching some pics of the amp board, pics of the schematic from rockford, and pics of the replacement part i have readily avaible.

Thanks in advance, sorry , english its not my first languague and electronics are not my field of work (i am a fireman), i hope i have been clear with my explanation.

2 pcs available, see photos. Never used, from surplus (Pollin surprise package).
€/$ 20 per piece
shipping to EU: €6
others: please ask

Payment: Paypal only

My mate has a 2 way speaker and in the photo of the crossover the 10ohm 50w resistor has blown hardcore and I reckon the cap was ok but the resistor popped so hard it shot a flame out and scorched the cap. Does that look like what happened? and what could cause this? It's the second time that resistor has blown :O
HF diaphram is open circuit but not burnt actually it still looks new.

Hi all.
Quick question that has likely been posed before:
If building a push pull DHT amp, e.g. Pete Millett 6A3 mono blocks, and using a single tentlab regulator per power tube, is there any benefit to having separate windings per regulator or can a single high-current winding feed both regulators without any significant penalties?
Thanks!

Thought I would share. Feedback is appreciated.

I picked up a 12' stick of 12" sch40 PVC and decided to make a couple enclosures. I also happened to pick up a bunch of 3/4" MDF at work.

I started by cutting the PVC to length. Then I traced circles onto the MDF. I cut out four circles of MDF and carefully sanded them until they were a light press-fit. Then I cut some rectangular pieces of MDF and used marine epoxy to laminate the circle to the rectangles.





Then I dressed the inside of the PVC with a 100-grit disc on my angle grinder.



I used some leftover West Systems epoxy from a boat project. This is expensive stuff, but extremely foolproof and very high quality.

I mixed up a batch and added cotton fibers until the consistency of peanut butter. I slathered it all along the circumference of the MDF disc and the inside of the PVC. Then I simply assembled the disc by squishing the PVC down over the MDF. THen I just filetted the extra epoxy. It has formed an extremely tenacious bond to the PVC.

Here is one tube assembled with my toolbox on it for weight until it cures.



I will then use a router to cut the MDF flush with the PVC leaving one side squared for feet.

More updates and photos as I progress.

Anybody recognize the manufacturers stamp on this??

thanks
Jeremy

I have a Millbank Talisman II amplifier, which is blowing its fuses.
It would be great if someone had a schematic, or an advide how to repair this kind of amplifiers.
This Talisman II amplifier is of the type Dynamic Loop System (DLS), and is constructed to feed a hearing aid loop in a meeting place.
The end stage transistors are 2 times 2N3055 and 2 times 2N3055H.
When the two fuses just after the rectifier/Elco's were blown, I replaced them with new ones.
After switching on, the amplifier became hot, smelled, and one of the fuses is blown again.
To fix this, I am looking for a schematic, or - even better - a repair manual for this kind of amplifiers.

I lost an OPT due to a bad valve and i didnt catch it in time.

So i either need a pair of OPTs, pp, for el84, UL tapped (preferably 25%)

Or a single hammond 1650 e

I am in the uk.

Thanks

Working on a 1 amp power transistor matcher.
It works around a transistor stage with base resistor and collector resistor with differential amplifiers measuring voltage across resistors.
From this it sends the plot to the pc via USB to display up to 5 different transistors at the same time.

A lot of buy in matchers are battery powered and often just use a couple of milliamps to measure the transistor.
This isnt a real world test as power transistors often work at amps rather than milli amps.
Most of the circuit is about generating a voltage ramp from a microcontroller then reading base and collector currents through differential amplifiers.
The microcontroller end is made as simple as possible and the heavy coding is done at the pc end.
You can zoom in on the 5 plots and run cursors along the plots to get Ic, Ib, Vc, Vb and Hfe at any point.

Owner stated this amp goes into protect. This is a Type 4 amp. It works until the amp draws about 15A from the bench. Input power voltage changes dont affect the outcome. When it pulls over this, the output waveform gets badly distorted and the amp also makes a slight buzzing sound. If pushed the amp will protect (DC offset?).

Any thoughts as to why the amp works <15A draw? Idles at 2A. Nothing shorted afaik.

Photo at terminals under load. 65hz sine wave.

WANTED TO BUY:

Looking for an excellent condition 12 inch: Jelco TK-850L MKII Tonearm, Ortofon TA-210, or Groovemaster I or III. Ideally boxed with all original accessories etc.

Sorry.. I mislabeled the heading.. looking for a Jelco TK-850L MKII.

Happy to consider alternate similar tonearms.

Happy to trade. Please see my available items here/diyaudio and US Audio Mart.

Thanks- Doug





Jelco TK-850L MKII Tonearm, Ortofon TA-210, or Groovemaster I or III.

I got four of these guys for cheap. They are probably designed for heavy duty thyristors with M20 stud mount. Dimensions are 70x80x100mm (base width x base length x height), the weight is about 800g. No specs of course. Can you estimate how mush power they can dissipate?

Hi All:
My Yamaha RX-V481 suffer the relay click sounds repeating issue.
Login to view embedded media
After open the case and comparing the service manual, the output stage relay is suspected.
But after I change the relay(RY221/RY223), the click sound repeating can't eliminate.
Have any one suffer the same failure problem?

B/R

For Sale:

4x universal regulator boards (https://www.diyaudio.com/community/threads/linear-regulator-pcb-lm317-lt1085-lm338-lt1083.254981/) - free! just pay the postage

SOLD 2x White SLB reg boards from XRK - £22 each
SOLD Mini-Me micro valve phono preamp board + 4 6N16P valves. (https://www.diyaudio.com/community/threads/mini-me-phono-preamp.242855/) This one was purchased from another member. There has been some work shown in the pictures - £25

1 Available 19v ACA kits I found in my cupboard! Each kit makes complete L&R channels. I only opened one for photographs.

Contains as per the listing (https://web.archive.org/web/2016031...products/amp-camp-amp-kit?variant=14849115012):

• Printed Circuit Boards
• Transistors including Linear Systems's JFET's and IRC MOSFET's
• Vishay/Dale Metal Film Resistors
• Elna Silmic ll and Panasonic Capacitors
• Bourns Potentiometers
• Rocker Switches and LED's
• Keratherm® insulators
• M3 board mounting standoffs, w/ bolts and washers
• Mounting bolts for Mosfets w/washers, high quality keratherm insulators
• Gold plated Speaker Terminals and RCA Jacks
• Power Connector Jacks
• Wire
• 2 laptop style power supplies suitable for the project

All you need to add is the heatsink/casework

Price reduction to £80

And why do we seldom see any results of bench testing of these?
Just curious from a guy who spent a lot of time in the lab.
And then 45 yrs selling test equipment to others.😀

I found this passive circuit online

http://web.archive.org/web/20070602004531/http://www.tkk.fi/Misc/Electronics/circuits/linesum.html

I need to connect the my left and right pre-out to my sub, the sub only has a single RCA inputs. If I use the circuit above, will it not affect the pre-out that goes to my main power amplifier powering the left and right speakers?

These are both Sovjet subminis.
2p5b / 2П5Б rod tube power pentode
6s6b / 6С6Б single triode mini
Any datasheet any language welcome.

So as I previously posted I found a Williamson 40/40 amp I cobbled together a LONG time ago, thanks again to everyone who contribute to that thread. So I gently woke the amp up, trimmed the bias to about 30 mA and hooked it to a set of Cambridge Soundworks Ensemble 3 speakers I found at a Goodwill for $40. I set it up in our bedroom, I'm driving it with an Amazon Echo Dot, and I cannot believe how nice it sounds... just so "sweet". The Ensemble 3 "subwoofer" doesn't have much reach so it's not great on hard rock but still it's a fun system to listen to folk music on.

The only downside to the system is that it won't play very loud because for reasons I can't recall I used a 24 VAC transformer so the DC rail is only about 32 V, this limits the output to about 7 W. So I'm thinking about building a true 40 W system with a 48 or 50 VAC transformer. One obstacle I'm facing is that the design is over 40 years old so most of the transistors are hard to get now, so I'm doing LTSpice simulations with parts with better availability. However no matter what I do I can't seem to get reasonable distortion results even with lots of output bias - about 90 mA static in the attached example.

Attached is my latest iteration. Some changes I've made:
#1. Changed output bias generator to Vbe multiplier for greater flexibility.
#2. Changed output transistors to FJA4313 and FJA4213 which are about the beefiest TO3P transistors I could find.
#3. Removed the output current limiting stage since the transistors look like they could withstand quite a bit of abuse.

The attached LTSpice simulation shows just under 0.5% THD at 1 kHz and 15 W output. There's a lot of odd harmonics in the FFT which made me think of crossover distortion but if you decrease the input to 50 mV pk-pk resulting in under 50 mW out, there's no visible crossover artifact. Also the distortion goes up to over 1% even though it appears to be in Class A.

I'm stumped as to the cause of the distortion, can anyone give any insight?

Thanks,

tommost

Hello I’m looking for Suggestions and electronic advice on starting this project.

The goal is to…

-trigger the four percussion sounds from the 1970’s drum machine Of the farfisa matador-r
using midi /relay interface from a Daw to create original drum patterns

-Add in a seperate audio line out for each four percussion sound so they can be Routed through individual effects in filters To a mixing desk for panning and eq adjustment.

I shall continue posting as The project progress please any advice would appreciated.
Thankyou

Recently acquired free box of tubes(pic)- Have another box full from young age tearing down old TV chasses...(plural??)
Want capability to eval before developing circuit for any of them, so think tester is wise 'maturing' hobby investment. Found article in link below informative:

https://www.radiolaguy.com/info/Mutual-Emission.htm

Decided on mutual conductance design, as I like the idea of introducing varying signal to the grid(s) instead of static voltage tests (emission)- if I understand it correctly ;<)
Also wanted capability to test later design (ie 60's) tubes and compactrons. So despite dizzying array of different makes and models- the Hickok 799 seemed to fit the venue. Also of interest the Weston 798-5B. Requirements moving forward were availability of good calibration and operations doc's, and houses for service if needed. The Hickok filled all of these, imo.

Would like to hear from those who have used these examples , and perhaps other rec's..
Thx,
Jim
ps. ordered this info to help w/ determining if the 799 has what I'm looking for
https://www.ebay.com/itm/122241588309

I did not realize that Metallized Capacitors ("Condensers") were developed by Bosch in Germany in WWII and taken-over by the US government.

Smaller, cheaper, for many reasons. Zinc is about the cheapest conductor. Zinc vapor is thinner than any foil we can wind. Just spray, no heavy rolling. Zinc vapor will burn-back at any defect in the paper, "self healing", over-rate your paper. Actual foil caps have become rare except atom-bombs and a few audiophiles.

I’ve had a lot of trouble finding transistors from the usual places and them not being fake, so I wanted 2SD669A & 2SB649A also 2SC3241 & 2SA1358, I decided to try Cricklewood I’ve used them many times especially in the late 70’s & 80’s and always been fine, but 2 of the transistors 2SD669A look like they are made by Hitachi as it has there good old logo on it, my question is has anyone used these transistors (which are not made like the good old days brass based tinned in silver that’s how I remember all the transistors like BD131 BD433 BD140 etc etc and many power it’s) and work fine I’m sure if you used them for low voltage low current switching they should be fine.
The amplifier voltage rails are +55 -55 so when they blow they go with a bang 110volt so fakes take off.
Here are the pictures

I recently got a Rane 6 channel amp. Testing it after unboxing, it seemed a little lifeless on the high end. So I did a quick FR measure (each channel measures identical) and it's down 3.5db at 20kHz, starting at about 6k. Spec is 20-20k with no db part mentioned. I verified my test setup using another SS amp which goes right out to 20k flat, then falls off.

I simplified the schematic to make it less of an eye candy. The input op-amp has a bandwidth limiting cap, but its spec says that rolls off starting at 50kHz...

It's understandable why they designed it that way, as it has to drive whatever a system installer can throw on its output. I promise to be more gentle with loading. Thank-you for any insight toward modification to change this aspect!

I have recently acquired a 1956 Montgomery Ward 3-Speaker Console (2 Jenson 8 in. Woofers and 1 Jenson 3.5 in. Tweeter) and am looking for a little information on the amplifier in the unit.
More specifically, I am attempting to locate the Dayton replacement capacitors, in order to bring a little life back into the old beast and get rid of the nasty buzz and heat associated with the leaky paper caps. Attached pictures are what I've got so far from the console.

I've been playing around with my 2 NAD 3020 Series 20 amps today. They've both been recapped and serviced and sound excellent, but both have a low volume hum on the right channel of the preamp that is not present on the power amp output. It's a bass frequency around 100 Hz that does not respond to the volume control but increases in volume with the bass control, as you might expect given the frequency.

This is a bit annoying to say the least despite the low volume of the hum. I do have sensitive hearing and now I've noticed it, I can't stop. I can make it go away by turning the balance dial all the way to the left channel or removing the pre-power links for the right channel. It would be nice if both channels of the preamp were as clean as each other. BOTH of my units are going this. I hope it isn't normal!

Any ideas what could be causing this? I replaced the 4 1N4002 rectifier diodes in one of the units without change.

F5 amp up for grabs. Nice condition looks new.

25Watt on DIYaudio F5v2.0 pcb.

£350.

I think the chassis and parts alone exceed this price.

Heavy piece of kit so collection only. Sorry.

Please excuse me if this is in the wrong section - Just joined the forums and am finding my way around.

I am working on a bunch of modifications to my KEF Q350s, including fully active crossover via DSP. One of the main issues with these speakers is two chassis resonances at 700hz and 1.2khz that I don't think I can fix with DSP as shown by this waterfall:





I have very little experience in dealing with such resonances physically - is there any "easy" way to reduce them, perhaps via polyfill or another damping material?

Thanks 🙂

Is this SMPS: https://connexelectronic.com/product/smps300re/
suitable for the Rodd Elliott P3A amp? https://sound-au.com/project3a.htm 60W class AB

I know SMPS have come a long ways but I can't shake the years of "look how big of a transformer this amp has" so I just want to verify that it will be fine for it.

thanks,

Has anyone compared Purifi vs. Ncore? Or even Ncore vs. Ice/Pascal/etc. ? What were the sonic differences, if any, and where (treble sophistication, bass, resolution, etc.)? Searchs aren't pulling anything up

I made a capsule microphone amplifier according to the circuit diagram circulated on the network

Working with 48V phantom power supply

But when I finish, it won't work properly?? The microphone has no sound

I don't know if there is something wrong with the circuit diagram. Please help me

Thank you.

Any chance anyone has a single Peerless DFM-2535R00-08 laying around - perhaps something they purchased for testing - that they would be willing to sell?

I'm adding more caps to my crossovers and have some 28AWG upocc solid silver wire. Is that wire OK to connect the caps to the 18AWG leads going to the AMP inputs and speaker outputs.. See attachment.

Hi everyone,

I have received my Alpairs 10.3 from Madisound.
I plan to build either the simple reflex ov9 or the pensil. The difficult part on both designs seems to be the hole and the groove(?) where the driver gets inslalled.
Are there big sonic differences ?

I have put the divers on random wood boxes so I can hear them right away. I am quite impressed, nothing comparable to Lowther DX3 I had a few years ago. Alpairs are much more listenable and easy on the ears.

Is it okay to break them in, in any box ?

Walter

Are there any 4-Channel DIY DAC projects out there?

Notes:

• I've built a MIDI controller for DJ'ing, and I'd like to add a DIY DAC with a main audio out + headphone out for cueing/previewing tracks.
• Looking to make an upgraded version of this interface: https://www.sweetwater.com/store/de...ktor-audio-2-mk2-2-channel-dj-audio-interface
• Is it difficult to add separate volume controls for the main / headphone out?
• Is it difficult to have a cue mix knob?

I'm about to take delivery of a pair of these, both used, they are definitely older units, dating back about 15 years most likely.

One is said to work perfectly, the other has "static" in both channels, and I'm getting it primarily for parts back up to keep the other one in service longer, or, possibly for repair and use.

There are only 4 boards inside. One for display, one appears to be off to the side to drive the transport, one is obviously the power supply, and one handles (presumably) the D/A conversion, and pre-amp section to drive the outputs, balanced XLR and RCA. (Discounting the optional HDMI board, only one of these has it)

Is it possible to generalize whether the fault is most likely in the PS vs the board for driving the outputs? I'm suspecting that on the A/D board/Preamp board that some caps are past their prime, swollen or leaking etc...

Is there much danger in swapping in the known good preamp board into the static one to test if the problem is on that board? Start with PS board swap instead?

I don't have a scope to watch the signals unfortunately, and I know that limits my ability to find the problem, but on many other projects, replacing caps has worked well, and usually visible changes are apparent. I'm just surprised Krell would not have put "overkill" caps in place where needed.

Thoughts?

Hi,
has anybody a guide how to add new parts, models in LT-SPice ?
I tried some guides from Web, but no works.

If anybody has a simple guide or sample for a how to add a new Part
, here a OPAmp NE5532 then I was lucky.

kind regards
Micha

Helo. I want to build a power amplifier. F6 looks like the simplest. My speakers are troels gravesen jenzen next. They are ratet at 87 db so I would need to biamp. From what I understand several off the pass design is lover gain than "normal". So my question is: what class d amp to pair with the f6. I might Explorer the 6-24 biamp curcuit and remove pass filter between bass and midrange.

I also use convultion filters for bass in roon dsp.
For preamplifier I have and aikido 6sn7 octal.

Dear guy

Do any body have the schematic of SONY TA-1120F can provide to me?
or where can buy the service manual?

not TA-1120 & TA1120A !!!!

Thanks you very much!!!

olay.chang@msa.hinet.net

Hi,

I would like to know if there are known circuits that permit to have low-noise dual power supplies at +200 and -200V for circuits that need less than 100 mA.

Thank you in advance,

Kind Regards
Roberto

At the end of my many page reading around an EL34 SE schematic I am still very confused as to which schematic I should use to have a very good non ultralinear amplifier with about 5 or 6 watts. I already have 2 ISO (ISO Tango) FC-12S output transformers and would like to use these. I would have liked to have bought a pcb from Tubelab, but George doesn't ship to Italy.
My loudspeakers are Troels Gravesen's PMS (... but my room is small and I don't listen at high volume). The source is Cocktail audio X14).
Any advice would be greatly appreciated
Domenico

I have a problem... I have started collecting old guitar amps. That combined with my cheapitude means buying amps that may have problems of their own.
In fact, as we speak, I'm thinking about getting one that has known problems, and as I was looking to see what could be involved I came across a thread on the very issue which offered both advice I could already give myself and advice I hadn't even thought of.
I think you guys are going to be a great resource.
I hope I can give back a little.

Oh yeah, I also have some vintage stereo gear I may start diving into...

Hi All anyone in U.K. with a pair of Dynavox LY302F surplus to requirements that they wish to sell new or used fine
Thanks Simon

Hello!
I need a pair of peerless DA32TX00-08 tweeters to go with the pair I have (replacing the Focal T120's on my Sapphire II's). Does anyone have them, and would you like to sell them?
Thanks,
Paul

Hi,

Long time member and a long time since posting. I now have my system back up and running after many years. I have a ADCOM 5800, a Pioneer PD-19 CD jukebox, an Onkyo CP-1038A turn table, a Marantz HEOS NA-6006 Network Music Player, a NAD 7240PE Receiver being used as a pre-amp, and Magnepan MG1.6/QR speakers. I bought the speakers in December 1998, shipped them to Magnepan in February 2021 for a factory rebuild, Magnepan shipped them to Peter Gunn, and he did his modification to the speakers.

I love the sound but I do have an issue with the ADCOM so I am considering a different amp that I will create a new post in the appropriate forum.

I do not have a dedicated listening room so the system is in my living room.

Are there any forum member in the Albuquerque or Phoenix area, maybe Denver, Cheyenne, Rapid City are? I travel to those places to visit family and friends is why I mention them.

I built a dual 10" box on a tight budget for a coworker, to fit up against the back seat in the trunk of a Honda Civic.


CompR10 as measured, 2 ohm DVC in series for 4 ohm

They already had a pair of kicker CompR10's, which is a high Q (.8 qts measured) driver, so I tuned it down quite a lot from kicker's recommendation to avoid a truly massive hump around 60hz. I like bass, but I'm only interested in 'lots of it' under 30 or 40 hz, and even after cabin gain I think it would have been way louder at 60-70hz than 30-40hz, which is not something I enjoy. This person had liked a previous build I made with the same frequency response shape goals in mind, so I went with my gut. (never posted it, but it was basically an LLT for a pair of GRS 10SW-4; around 2.5ft^3 each tuned to 35hz. Ginormous box, but nice deep bass for the budget, pretty smooth frequency response with no big peaks, and it uses a tiny amp that doesn't dim the lights)

I hear a transmission line is The Way To Go to tame/use high Q subwoofers, does anyone agree that would have been a better idea than just downtuning a bass reflex?


Kicker's recommended minimum size vented in red (both drivers) : 2.5ft^3 @ approx 45hz. (Port is 42 square inches by 20 inches long)

I went with (Green line): 2.5ft3@ 30hz (port is 25 square inches by ~26 inches long).

Max vent air speeds are lower above 32hz, higher below that, compared to kicker's design. Excursion is higher around 50hz, but far lower down low. Group delay is better everywhere above 28hz. I considered those acceptable tradeoffs for a better natural frequency response.


Hornresp

The vent joins up in the middle; it is half width on each side. I don't know if there are any downsides to this; I've seen commercial designs where they brought the ports to the middle the same way, but then left a divider board in between them. Seems like a waste of space and weight to me? The port is braced to the back in several places and across the middle at least once; those aren't in the 3D design and I didn't take a lot of pictures.



I used one fifty dollar sheet of 3/4" shop ply for the exterior (it looked better than the alternatives), and some 1/2" baltic birch I already had for the inside port walls. I delivered it rough and they finished sanding and painting it. No measurements (I think I took an impedance sweep to confirm the tuning is all) and no final photos, apologies. Reports are the user is happy with it. Fits well in the trunk, with room for excursion before hitting the seats, and very little wasted space on the sides.

Hello valve fans! I have a recently completed Single Ended amp for sale with Svetlana 6C4C outputs, which are a 6.3V version of 2a3 also called 6B4G. These are directly heated with DC regulators by Rod Coleman. Input stage is switchable between 6J5, gain of 20, and E180CC, gain of 46 so you can use either depending on the sensitivity of your system. OPTs are Techno, 5K. Like all 2a3 amps this will only give you 3-5 watts but that's plenty loud enough with speakers around 90db in medium size rooms.

Aesthetics are rather industrial, but all parts are premium quality like teflon and DC Link capacitors, Holco and Russian military resistors and 4mm aluminium top plates. You don't get that with most commercial amplifiers. The amp is in 2 chassis with a separate power supply with GZ34 rectifier. I like this amp a lot and really enjoy its sound.

Collection preferred from Kensington, London, but can also be posted within UK. Asking £585. £545 £525

Audition for a week is fine, so sale or return at buyers expense.

audio cables seems to split the earth in two, one part of those who can hear and detect anything and the other part who can not hear anything, what is the real truth here?

this article about kimber kable naked and its very steep price (in my world that is), how can this kabel not be better in sonic then a simple lamp cord?

https://www.hifinews.com/content/kimber-kable-naked

In my callow youth I built one of this using point to point wiring because I couldn't afford the pcb. Cleaning up the basement I found it.... I carefully brought it up and son of a gun it still worked. It has a 100R trim pot for bias adjustment, I searched and couldn't find the article anywhere so I'm not sure how to adjust it. Does anyone know? Thanks in advance.

Hello. I am starting to form an idea for a speaker design using Peerless SLS 830668 subwoofers and Usher 8836AC2 midwoofers. Here are the spec sheets on the two:

https://audioalchemy.ro/difuzoare/usher/296-608.pdf

https://www.parts-express.com/pedocs/specs/264-1110-tymphany-sls-p830668-spec-sheet.pdf

How should I go about choosing a crossover point?

My intuition told me that I should aim for a crossover point around 100-200Hz, but looking at a speaker design using the same Peerless subwoofer (Paul Carmody's Tarkus) I saw that he crossed his speaker over at around 400Hz.

I have historically thought of subwoofers or bigger woofers as having the function of picking up the slack that a midrange/midwoofer driver struggles with. I have intuitively thought that so long as a midrange or woofer driver is capable of producing a frequency at high SPL's without much distortion, that it should be given the task of producing those frequencies as it will simply do a better job of reproducing those sounds given that it is smaller and presumably more controlled, with better directivity.

I have read that you should cross a tweeter as low as you can, because if it is capable of producing lower frequencies at a high SPL without distortion, then it will almost invariably do a better job than whatever larger driver it is crossed over with, on account of its smaller size. Here is a quote from Danny Richie of GR Research:

"You are much better off allowing the tweeter to cover as wide of a range as possible and cross as low as the tweeter will allow. And it doesn't matter how good you think your full range driver is. Any tweeter from 2kHz and up will outperform it in every way. It is just flat out going to have better dispersion, speed, and resolution due to its smaller size and much less moving mass"

I know Mr. Richie has a talent for ******* people off, but this makes sense to me. Taking this as true, does this concept not apply to crossing over a midwoofer and subwoofer? Could Mr. Carmody have yielded better results by lowering his crossover point? What reason might he have had for crossing over his Tarkus speaker so high? Or am I just completely confused here? He chose quite a large midrange driver for his Tarkus, so it just seems odd to me that he wouldn't take advantage of its broader bass extension.

Here is Mr. Carmody's writeup on his Tarkus speaker. I bet it kicks *** 😎
https://sites.google.com/site/undefinition/floorstanding-speakers/tarkus

I am new to speaker design, but I am very curious to learn! Thank you in advance for your responses!

Hi, I recently came across this Github library for PCM5142 and other family members: https://github.com/SilverSho0t/PCM5142

Has anybody hare used this lib? My primary interest is to run the chip with custom FIR filter coefficients.

Both the code and TI use the word "DSP program". Would that be a binary or a coefficient file? Either way, is there documentation on how to write those?

I have been in contact with TI support which basically said "there used to be a code but we pulled it from the market and you get nothing". They do offer some ways to write biquad and mixer parameters but not FIR or full-blown custom DSP code.

I'm quite happy with the PCM5142 out of the box. But I have a library of special FIR filters that I would really like to move from my $$$$$ Xilinx FPGA + PCM1704 prototype and into something with a bit more widespread availability

Any info on PCM5142 DSP core welcome!


Thanks,
Børge

Hopefully some experienced people can offer advice here.

I'm sitting on a large stash of 40 x Peerless TC9FD18-08 and 40 x SB acoustics SB26STCN with the intent of building a large 2 way array inspired by the fullrange version many people have already built. The reasoning for the 2 way implementation of these drivers is trying to get a more dynamic and coherent HF response - I like the way the TC9 drivers sound up to about 8k, but the HF response past that isnt that great. The additional reasoning was having a tighter driver spacing thanks to the smaller diameter soft dome drivers to reduce combing. These little soft domes sound very good being they only cost me $26 each. I've used these in other projects and they sound alot like a higher end SB soft dome, so IMO they are a worthy choice for an array.

I planned on a 20 element array per side for both LF and HF sections using the tightest possible driver spacing. This means I may truncate the HF driver faceplates to get them spaced even tighter for the least amount of combing. The processing, EQ and crossover was initially going to be DSP, then active analog once the main EQ curve and crossover was established.

I took some inspiration from these threads -

www.diyaudio.com/community/threads/full-range-tc9-line-array-cnc-cabinet.303417

www.diymobileaudio.com/threads/lord-of-the-waves-the-two-towers-a-25-driver-line-array.114489

www.roger-russell.com/ids/ids.htm

Does a 2 way implementation of this type of an array sound like it has the advantages I'm looking for, or am I opening up a bigger can of worms? I know the horizontal dispersion will suffer a bit with the side by side driver arrangement, but i wanted the more precise sounding treble of the SB soft domes with lower distortion and headroom to spare. Any constructive thoughts?

Nowadays there are lots of resources available to help with LC filter design, the one I use most is at https://rf-tools.com/lc-filter/. This site is invaluable but it only gets a design so far, as soon as you use real-world inductors (i.e. with losses) then the very nice flat, even equi-ripple response the math gives goes out of the window. Over a number of years I've developed a way to try to restore flatness and evenness to a filter incorporating real-world inductors but haven't documented it. I did mention it to Elvee here though. I figured it was probably worth fleshing out the steps in a relatively short blog post.

RF-tools allows you to specify your passband ripple - meaning the variation in frequency response in the passband. In general, the higher the passband ripple, the higher the Q in the filter. Introducing losses (inductor DCR) lowers the Q hence we need to aim for higher Q when designing than we actually need. Which means design for higher ripple and it'll be reduced when real inductors are substituted. The amount of additional ripple is going to depend on how lossy your inductors are - I find typically its in the region of tenths of a dB with relatively high Q ferrite-cored inductors.

Next up comes the corner frequency - we need to aim for a higher corner frequency than we need in practice as the process of straightening out the frequency response inevitably lowers it. Lastly, the terminating impedance needs to be specified higher as we'll lower that on the way to optimizing the design.

Another aspect to be considered is - are you winding inductors yourself or going to buy them off-the-shelf? In both cases inductor values are quantized but off-the-shelf inductors are much more coarsely quantized in values than self-wound ones. Some ranges are only E6, E12 is fairly common but E24 is rather rare. If you specify the corner frequency and the terminating impedance tightly then you'll have no flexibility over what inductor values fall out of the design process. But normally those two parameters are at least a little bit flexible, so it makes sense to aim to hit an inductor value which is available. This isn't at all difficult when there's only one inductor in the design, but what about higher order filters?

Hitting off-the-shelf inductor values with a 5th order filter (two inductors, three caps) isn't too hard but does take patience and a certain amount of flexibilty over the end result. You can get the two inductors both to fall on off-the-shelf values if you give up control over the pass-band ripple as the ratio of the two inductor values directly relates to the ripple parameter. With more ripple, the inductor values move closer together - by 10dB ripple (altogether quite useless for audio) they're practically co-incident. Moving the other way, having no ripple at all makes for an effective Butterworth filter with a 1.9 ratio. So you can see with E12 values you'll have a choice of ~20% or ~45% or ~75% ratio between inductors and this gives a choice of three ripples - ~0.3dB, ~0.01dB and effectively flat. With lower ripple you lose stopband rejection so the 0.3dB option is the most attractive one to me giving inductors with next-door values in the E12 series.

(to be continued)

Is there any way to find out if you are on someone's ignore list, particularly if you are on the thread starter's ignore list?

It could save some time when you know that there is no point in answering someone's question because they won't read it anyway.

Has anyone got any recondition where to buy Genuine 2SC5200 & 2SA1943 Mouser and Profusion have neither in stock, AliExpress I have 6 of these hear nice magnetic backs and get dam hot that’s the good ones the bad ones take themselves out and the divers.
Amazon and eBay is again pot luck, RS have them in stock works out quote expensive but they are Toshiba, but I understand they are no longer made so how do they have them I can’t believe RS would be fakes.

I have a un-assembled as new TemaadAudio 12'' Uni-Pivot Tonearm Kit that I will never get around to use now. makes up to a high arm of around $1,500 (depending on the wire you use)

Price US$260-00 worldwide postage available, would swap for MC cartridge

Photo 1 is what kit contains

Photo 2 is same arm made up from L/Heaven

Does anybody know if it is possible to source heatsinks for tubes?

I wonder if there is a sweet spot in the LM3886 gain setting and in the optimal input/output voltage that will give the lowest THD?

I've heard setting gain to 20 sounds way better than gain of 10. I'm assuming that is because of lower THD?

Hi Guys,
I got 2 problems probably connected:
I recently built a sub and I also put together the amplifier with some aliboards and a Dayton LF.
The Amplifier is a L15DSMD irs2092 and the PSU is a 350W +-50V +12V (More 250W than 350W...).
Here the links to the actual parts:
PSU
Amp
Preamp

Whitout preamp:
When I start cranking the volume it goes into protection with a rather low volume. Everything shuts down and turns on again and keeps doing it and the volume is quite low compared to the main speakers (Small and not very sensitive JBLs guess 85/87 Db)
So low volume, barely usable, have to set the sub channel to +6db to have a balanced output with the mains (Sub volume 100%)

With preamp:
I also have a preamp board (Actually 2 and it happens with both), but if I try to connect them even more problems kicks in as it goes into protection right away without even music, if I disconnect the power to the amplifier or to the board everything stays on at least without or with low music. If I disconnect the Load everything stays on.

In your opinion is it a problem related to the amplifier or to the PSU ro what?
The sub is an Infinity 1240W 12inch 4 OHM in a 35l sealed (the Dayton is currently set as pass trough).
The input signal is from the sub channel of a Cambridge Azur 351R.

Thanks for any hint you can give me! Don't really know where to look!
I'm a mechanical engineer, so I'm crap at EE...experimenting and learning...🙂

D.

I have a repair shop. Just answered another email from a new customer telling me that he thinks his "amplifier just needs the capacitors replaced".

While, yes, sometimes indeed the caps need a swap, it's silly how the general public seems to believe that every audio issue in their world is caused by the need for a "caps swap." Where did this begin? How can we stop this?

conditions which people have tried to convince me can be repaired with a caps swap:

"my amplifier won't turn on" - caps swap
"one channel is really distorted" - caps swap
"smoke came out and then it sounded really bad" - caps swap
"I heard a pop and now there is no bass" - caps swap
"I found this speaker outside and thought it might still be good" - caps swap


Stay tuned for part II: "just needs a little solder"

"I had an issue with an am tuner the adjustable potentiometers they were very hard to move but I was able to get the iron material cap unscrewed and found a lube on the underside of the cap so I took some of the lube under the cap and put some onto the treads of the iron cap then screwed the cap back on and now no more issues it moves freely now but, I was wondering if anyone knows the specific type lube used on these types of components etc. (non conductive perhaps silicon type lube not sure) the iron caps can very easily break when they get stuck etc. without the lube on the threads etc."

Hi,
I would like to know what is the dielectric of these green WIMA caps ??

I supposed they are not Polypropylene because WIMAs PP are usually red, but I have never used green Wimas so I don't know.

Thank you for your reply,

I have a Topping D90 (non-MQA) for sale.
Purchased it a little over a year ago and put to sparse use.

This is the original version with the now rare AKM4499 DAC.
Unit is like new and comes in the original box with remote.

Asking price $649 + shipping (US only) + Paypal fee.

thank you.

This is my first post on this site have gotten lots of great info in the past on here. Today i got a kicker 06zx700.5 that had a non working sub channel. amp would power up green and play on the 4 channel side. so i took it apart found one of the subwoofer side power supply fet blown along with the 100ohm resistor replaced with new irf 3205. before i did that i checked all resistors and gate supply voltage everything was good. now with the parts replaced amp goes into protect checked all ouputs and output resistors and everything is ok. but i did notice if i removed the card (pas315-02) that it would power up green and stay that way but once i plug it back in it goes right back into protect and kinda goes in and out of protect every 4-5 seconds. im not a pro at this stuff but i have repaired 40+ amps in the past with success and never had problems after that but kicker amps get me every time hoping someone could help me please and thank you.