R44 is dead shorted? Q17 tests OK but what is seen at it's base when sine wave is coming in?
You have symmetry here to your advantage so scope out things on the positive side and compare to the negative side.
I am considering purchasing the kit soon, so I am very interested in your experience.
You have symmetry here to your advantage so scope out things on the positive side and compare to the negative side.
I am considering purchasing the kit soon, so I am very interested in your experience.
R44 is not showing any current through it; no voltage drop across it. The resistor itself is fine. Same with its symmetrical twin R29. Which is really weird to me.
But I'm learning how to reverse engineer the schematic and signal flow, so I'm doing a bit of trial and error and a lot of thinking and grasping at concepts. Which is how one learns, I suppose. I might be barking up the wrong tree even looking for current though R44.
Project-wise? Advanced-intermediate. It probably shouldn't have been my first but I did grow through it.
Sonically, it's been a delight and joy.
But I'm learning how to reverse engineer the schematic and signal flow, so I'm doing a bit of trial and error and a lot of thinking and grasping at concepts. Which is how one learns, I suppose. I might be barking up the wrong tree even looking for current though R44.
How are your soldering skills? They'll be improved by this project, no doubt. Quick tip: when seating test point resistors R 12,24, 13,25, 16, 39, 44 into the board, leave enough leg-room for multi-meter grabbers for the calibration and testing of the boards.
Project-wise? Advanced-intermediate. It probably shouldn't have been my first but I did grow through it.
Sonically, it's been a delight and joy.
My soldering skills are excellent. Thanks for the tip regarding test and calibration points.
As I indicated, I think your best bet in locating your issue is to scope probe and compare between the positive an negative rail circuits.
Very curious to see what has failed. One of the benefits of not being an early adopter
As I indicated, I think your best bet in locating your issue is to scope probe and compare between the positive an negative rail circuits.
Very curious to see what has failed. One of the benefits of not being an early adopter
Put the schematic into LTSpice and you can learn a lot. One thing you may learn is 'Ol Erno was pretty darn smart. There are kits with fancier topology, but a few small tweaks can make the original circuit even better. I am so happy I refurbed my old modified 120. So sweet. Should have kept a few of my 220s I guess.
Oops, I wasn't clear.
This is the 220-C from our friend Bob Cordell, not the original DH-200 front end. So I'm not going to put Bob's circuit into LTSpice as there are some 100+ components in it from the IPS to the VAS to the DC servo, etc. (Plus I'd have to go through the learning curve on LTSpice).
I've got time and patience; each time I read through his circuit descriptions and watch his burning amp presentation I understand a little more, but I'm at the stage of my education where I'm getting the gist of some of the jargon and doing mechanic's work: if I don't have signal here, what's the point upstream where I do have signal?
This is the 220-C from our friend Bob Cordell, not the original DH-200 front end. So I'm not going to put Bob's circuit into LTSpice as there are some 100+ components in it from the IPS to the VAS to the DC servo, etc. (Plus I'd have to go through the learning curve on LTSpice).
I've got time and patience; each time I read through his circuit descriptions and watch his burning amp presentation I understand a little more, but I'm at the stage of my education where I'm getting the gist of some of the jargon and doing mechanic's work: if I don't have signal here, what's the point upstream where I do have signal?
How many front end pcbs have you built?
Is this the results of a first time power up test?
No need to pass a AC signal thru if you can not get it to bias up properly.
It is hard to say what exactly. Check all the components for the correct ones, orientations, in the VAS, Q7,12,7,18
You wont get proper OPS bias if the front end is not op properly.
Good Luck
Is this the results of a first time power up test?
No need to pass a AC signal thru if you can not get it to bias up properly.
It is hard to say what exactly. Check all the components for the correct ones, orientations, in the VAS, Q7,12,7,18
You wont get proper OPS bias if the front end is not op properly.
Good Luck
Oh, this was my first PCB build, throughout last year. A steep learning curve and definitely forced me to up my game. And my skills have improved greatly
I went through birthing pains in September / October last year in this thread. I had it running for a couple of months, but then this current issue.
I’m only working on the AFE in the bad channel at this point given the DC offset as shown by the AC signal images- that was just scoping the AFE driver wires, no OPS.
diagnosis progress: all resistors and diodes on the AFE fine. Which leaves…
me to finish my Manhattan and take it up again tomorrow.
I went through birthing pains in September / October last year in this thread. I had it running for a couple of months, but then this current issue.
I’m only working on the AFE in the bad channel at this point given the DC offset as shown by the AC signal images- that was just scoping the AFE driver wires, no OPS.
diagnosis progress: all resistors and diodes on the AFE fine. Which leaves…
me to finish my Manhattan and take it up again tomorrow.
Update.
I checked all the BJTs for shorts and diode drops from base to C and E, and vice-versa on the P-types, and reflowed any soldering that looked even remotely questionable.
Now I've got it out of the testing TP1 jumper position, hooked up to the OPS, and RV2 is letting me set the bias on the output MOSFETS. With 30mV bias, I've got a steady 1.6V dc offset at the speaker terminals without any signal or load, and that offset goes up with more bias. Still, better (for everyone, especially speaker drivers) than 16V. I'm on an isolation transformer->variac and have the rails at +- 55V
It's progress.
I'm wondering if a transistor in the negative side is on its way out.
I'm going to start poking with a scope at various points in the signal path to compare sides and, if necessary, compare channels.
I checked all the BJTs for shorts and diode drops from base to C and E, and vice-versa on the P-types, and reflowed any soldering that looked even remotely questionable.
Now I've got it out of the testing TP1 jumper position, hooked up to the OPS, and RV2 is letting me set the bias on the output MOSFETS. With 30mV bias, I've got a steady 1.6V dc offset at the speaker terminals without any signal or load, and that offset goes up with more bias. Still, better (for everyone, especially speaker drivers) than 16V. I'm on an isolation transformer->variac and have the rails at +- 55V
It's progress.
I'm wondering if a transistor in the negative side is on its way out.
I'm going to start poking with a scope at various points in the signal path to compare sides and, if necessary, compare channels.
Note: when one* properly places the test jumper back to the operating position as opposed to missing the middle pin, DC offset issues tend to go away.
This was not the initial problem, rather one encountered while debugging and testing. Post mortem: I'm going to go with it being a bad soldering connection in the AFE yet again. Because this amp insists on being my education on learning skills the hard way.
Here's Queen's All Dead at <1 watt. Letting her run for a while.
*That would be me.
This was not the initial problem, rather one encountered while debugging and testing. Post mortem: I'm going to go with it being a bad soldering connection in the AFE yet again. Because this amp insists on being my education on learning skills the hard way.
Here's Queen's All Dead at <1 watt. Letting her run for a while.
*That would be me.
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Well, the joy is back. I did get it all sorted, so now it's two months and about five hours of joy and counting.
At the moment, it's sitting in the room with my pool table, driving a pair of Snell B- Minors, fed by a DAC and an Aragon 24k pre. Though the room isn't ideal for serious listening (there's a huge pool table in there!) I find myself pausing in the middle of some practice shots to marvel at the DH-200C's effortlessness. A big room and big speakers will help deliver a big sound, but even this amp is doing a great job of clamping down on the Snell's 12" acoustic-suspension woofers. The bass is controlled; not an easy feat.
When I've had it in my main listening system, it has been neutral, very, very detailed and revealing. When you year hitches in Eva Cassidy's voice, you know you have some detail happening.
Hope this helps!
At the moment, it's sitting in the room with my pool table, driving a pair of Snell B- Minors, fed by a DAC and an Aragon 24k pre. Though the room isn't ideal for serious listening (there's a huge pool table in there!) I find myself pausing in the middle of some practice shots to marvel at the DH-200C's effortlessness. A big room and big speakers will help deliver a big sound, but even this amp is doing a great job of clamping down on the Snell's 12" acoustic-suspension woofers. The bass is controlled; not an easy feat.
When I've had it in my main listening system, it has been neutral, very, very detailed and revealing. When you year hitches in Eva Cassidy's voice, you know you have some detail happening.
Hope this helps!
Hi RsavasSame fets
I had never looked at an Iris schematics, nothing like a hand drawn schematic to work from
Just the boards set for upgrading my DH-200. However I am not able to access the cart with the BOM. An you pl check and send the correct way to access this in mouser.
Cheers!
May you figured it out by now, but the link is in the build instructions. https://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=6d2b011fe6
Hello
Good to know there is still interest in BC-1.
As an update, I think I am done with design and testing. I have my BC-1 prototype up and running now for a few months. I leave it on continuously as a long term reliability test.
As was done for Dh-220c, I was going to let Bob Cordell decide when BC-1 is ready for release. I assume when Bob has his prototype completed and tested to his satisfaction.
Would you be interested as a beta tester? Test the waters so to speak? As I think we are at or close to that stage now.
The design will be released as a 8 pcb set, price tbd.
Rick
Good to know there is still interest in BC-1.
As an update, I think I am done with design and testing. I have my BC-1 prototype up and running now for a few months. I leave it on continuously as a long term reliability test.
As was done for Dh-220c, I was going to let Bob Cordell decide when BC-1 is ready for release. I assume when Bob has his prototype completed and tested to his satisfaction.
Would you be interested as a beta tester? Test the waters so to speak? As I think we are at or close to that stage now.
The design will be released as a 8 pcb set, price tbd.
Rick
I would be. I have a couple of hulks to use as chassis / power supplies. A dyanaco400 and an old Urie amp. I may have to be flexible on the PS voltage and output transistor number (quantitiy). Thw pcb interest me in particular. I am a retired EE with skill, instruments, and time.