DIY gadget man Pedro.
Wow, this is an interesting thread.
Pedro, you are an exciting person!
A few other things you might want to check.
1) Always check for dry solder joints first. Can save a lot of time.
2)If it has blue resistors that look like metal oxide or composition type (matt blue finish) these can go high resistance. Check them.
3)If the small plastic case transistors have black like carbon on their legs for a few mm they could be junk. Saw a lot of old Sansui amps with the problem.
4) I have also experienced intermittent ceramic capacitors which were breaking down. They were the comp caps in the VAS stage. Heat sensitive as well. They give a popping static sound. Not a hum sound.
Is the amp oscillating at RF?
Do you have DC on the output and hence big current draw through the speakers?
If the output bias pots are in the base to emitter leg of the VBE multipler turn them to maximum resistance after changing the output transistors. This will result in minimum or no bias in the output stage when you turn it back on. Then adjust up slowly.
If thay are in the colector base circuit you have a hand grenade aka Yamaha A520. Swap the NPN vbe tranny for a PNP and problem solved.
After the blow up check output transistors, drivers, second stage and input stage. It is probably just the outputs and maybe the drivers that are shot. Use the diode setting on the meter and make sure you desolder their legs so you are measuring the right part and not something else in the circuit. Check the emmiter degeneration resistors of the outputs as well. The big white ones - may be o/c.
May the force be with you.
Craig.
Wow, this is an interesting thread.
Pedro, you are an exciting person!
A few other things you might want to check.
1) Always check for dry solder joints first. Can save a lot of time.
2)If it has blue resistors that look like metal oxide or composition type (matt blue finish) these can go high resistance. Check them.
3)If the small plastic case transistors have black like carbon on their legs for a few mm they could be junk. Saw a lot of old Sansui amps with the problem.
4) I have also experienced intermittent ceramic capacitors which were breaking down. They were the comp caps in the VAS stage. Heat sensitive as well. They give a popping static sound. Not a hum sound.
Is the amp oscillating at RF?
Do you have DC on the output and hence big current draw through the speakers?
If the output bias pots are in the base to emitter leg of the VBE multipler turn them to maximum resistance after changing the output transistors. This will result in minimum or no bias in the output stage when you turn it back on. Then adjust up slowly.
If thay are in the colector base circuit you have a hand grenade aka Yamaha A520. Swap the NPN vbe tranny for a PNP and problem solved.
After the blow up check output transistors, drivers, second stage and input stage. It is probably just the outputs and maybe the drivers that are shot. Use the diode setting on the meter and make sure you desolder their legs so you are measuring the right part and not something else in the circuit. Check the emmiter degeneration resistors of the outputs as well. The big white ones - may be o/c.
May the force be with you.
Craig.
I'll fix this thing even if I have to buy another amp. I'll just desolder all the components and resolder on my amp😀 (just kidding)
At this speed we're gonna make the 200000 views very quick!
I reccon june, juli...hope you don't fix that amp too soon PedroPo!!!
Another lottery???😉 😉
I reccon june, juli...hope you don't fix that amp too soon PedroPo!!!
Another lottery???😉 😉
I only can offer friendship!
No high end Pass stuff.
Wait a minute! I made a clone of Aleph 5!! nah!! I'll stick with friendship!😀
Hugo:
Did you noticed also that in the amp between the power devices the is a small component that in the board is marked as diode.
I guess this is some kind of thermal protection, since is near the sink.
Could it be damaged?
The flare came from that zone...
I'm ordering the transistors from farnell. they are pretty cheap, but they don't have 2sd414R and 2sc945 or your substitutes.
Any other sugestion?
No high end Pass stuff.
Wait a minute! I made a clone of Aleph 5!! nah!! I'll stick with friendship!😀
Hugo:
Did you noticed also that in the amp between the power devices the is a small component that in the board is marked as diode.
I guess this is some kind of thermal protection, since is near the sink.
Could it be damaged?
The flare came from that zone...
I'm ordering the transistors from farnell. they are pretty cheap, but they don't have 2sd414R and 2sc945 or your substitutes.
Any other sugestion?
Watch the flares
After all, without friendship this site wouldn’t exist..
The diode is (guess) a bias diode. It measures the temp from the sink and controls the bias. Here's the link how to measure diodes.
http://www.eatel.net/~amptech/elecdisc/diodes.htm
For the 2SC414 you could order BD139 (334-3315 Order code at Farnell) and for the 2SC945 witch is a bit difficult, you try BC546. However 2SC945 has BCE and BC546 has EBC pin out. Means you have to swap the pins. (434-784 Order code at Farnell)
I really start enjoying myself here!
As Mr. Pass states on Aleph's : "The amplifier will not be damaged by driving a short circuit, and it is probable that the only failures you will see will be random component failure."
Lucky you...
🙂
After all, without friendship this site wouldn’t exist..
The diode is (guess) a bias diode. It measures the temp from the sink and controls the bias. Here's the link how to measure diodes.
http://www.eatel.net/~amptech/elecdisc/diodes.htm
For the 2SC414 you could order BD139 (334-3315 Order code at Farnell) and for the 2SC945 witch is a bit difficult, you try BC546. However 2SC945 has BCE and BC546 has EBC pin out. Means you have to swap the pins. (434-784 Order code at Farnell)
I really start enjoying myself here!
As Mr. Pass states on Aleph's : "The amplifier will not be damaged by driving a short circuit, and it is probable that the only failures you will see will be random component failure."
Lucky you...
🙂
I believe that even aleph couldn't survive my aligator's 😀
As regarding the small TO92 2sc945 transistors, yesterday I swapped one of them with bc108C ( with exchanged legs, of course) and it worked ok.
First I check with the multitester in the HFE position, and found out that it was npn. then I went to my transistor case and start searching for npn transistors. I found bc108C and after a while I realized that I should turn the legs. not a problem. legs bent transistor soldered on and sound too 😀
this trial and error will kill me some day!
As regarding the small TO92 2sc945 transistors, yesterday I swapped one of them with bc108C ( with exchanged legs, of course) and it worked ok.
First I check with the multitester in the HFE position, and found out that it was npn. then I went to my transistor case and start searching for npn transistors. I found bc108C and after a while I realized that I should turn the legs. not a problem. legs bent transistor soldered on and sound too 😀
this trial and error will kill me some day!
PedroPO said:
I like trial and error, I didn the same thing with an amp I got that had 1 output transistor blown (how can only 1 blow, and why?) But one in, it worked, lasted for a month or 2, them blew.. 🙂 So, I went out and bought the HIGHEST power transistor I could afford, adn put it in.. 🙂 6 month later the original transistor in teh other channel blew.. 😛 I didn't want to buy another transistor, and have mismatched output stages, so I went and bought another 2 transistors, the same as the first one I bought.. 🙂 lol.. ahh, I wasn't payin for it.. 🙂 lol I don't buy audio equipment, its given to me. . 🙂 3 amps... (2 needed minor repairs) 4 tape players, a CD player, and a pair of speakers... this is probably why I wouldn't bother trying to fix another amp if it was given to me, and was going to cost to fix.. 🙂
Recently I found out that I love fixing and making things more than actually using them. Money is no problem, of course.
Another day I built a light box for slides, that costed me 2x more than buying a new one.
(am I going insane?)
Another day I built a light box for slides, that costed me 2x more than buying a new one.
(am I going insane?)
I like making things too.. 🙂 Like my new speakers.... I don;t listen to music, and my favorite radio station is AM, not FM, so its only mono.. 🙂 But I like knowing that I have the best quality speakers possible for what I paid.. 🙂 I also like knowing that my speakers can outperform lots of other peoples more expensive speakers.. 🙂 AND!!! I LOVE the idea that I made them myself (hopefully) About the hopefully bit...
I am PLANNING on making the boxes at school, I really don't have the tools or the knowledge to make them at home, I want to do a good job. I have bought good drivers for this reason.... BUT!!
I am not sure if the woodwork teacher at school will let me make speaker boxes for one of my main year 12 projects.. 🙁 I knwo in the past, a year 11 student wasn't allowed to make a subwoofer box, but that was just a box.. 😛 lol... I better be allowed too.. 🙁
I am PLANNING on making the boxes at school, I really don't have the tools or the knowledge to make them at home, I want to do a good job. I have bought good drivers for this reason.... BUT!!
I am not sure if the woodwork teacher at school will let me make speaker boxes for one of my main year 12 projects.. 🙁 I knwo in the past, a year 11 student wasn't allowed to make a subwoofer box, but that was just a box.. 😛 lol... I better be allowed too.. 🙁
SkinnyBoy,
perhaps if you can demonstrate to your teacher the detailed design required for good 'speaker boxes , and show him that there is much,much more engineering and design in this project than most school woodworking projects.... maybe he/she'll let you do it once you show it's not just a box 😎
Ray
perhaps if you can demonstrate to your teacher the detailed design required for good 'speaker boxes , and show him that there is much,much more engineering and design in this project than most school woodworking projects.... maybe he/she'll let you do it once you show it's not just a box 😎
Ray
Re: bribe him
and pay for both sets of drivers?? It would be cheaper to buy the tools I needed. 🙂 lol... I don't think I could make 2 pairs of speakers... not in 20 weeks with 6 45minute lessons a week.. 🙂
90hours.. 🙂 lol... Thats why I am planning the boxes as much as possible before I go back to school next week.. 🙂
PedroPO said:
and pay for both sets of drivers?? It would be cheaper to buy the tools I needed. 🙂 lol... I don't think I could make 2 pairs of speakers... not in 20 weeks with 6 45minute lessons a week.. 🙂
90hours.. 🙂 lol... Thats why I am planning the boxes as much as possible before I go back to school next week.. 🙂
TheFettler said:
Lol... but it is just a box.. 🙂 a finely tuned, well crafted box with the right size holes cut in the right places 😀 lol yeah, there is much design, adn research required.. 🙂 more than for a COFFEE TABLE!!! 😛 lol
Lol... but it is just a box..
thats like saying that the Aleph is 'just an amp...' or that a Ferrari is 'just a car...'
well, perhaps...🙂
ray
thats like saying that the Aleph is 'just an amp...' or that a Ferrari is 'just a car...'
well, perhaps...🙂
ray
Re: Lol... but it is just a box..
An amp is just an amp.... The Aleph is an amp is just an amp...
A car is just a car.... A Ferrari is a car is just a car...
A speaker box is just a box... My speaker boxes are just boxes.. lol SUPRISE SUPRISE!!
TheFettler said:
An amp is just an amp.... The Aleph is an amp is just an amp...
A car is just a car.... A Ferrari is a car is just a car...
A speaker box is just a box... My speaker boxes are just boxes.. lol SUPRISE SUPRISE!!
PedroPO said:
You realize of course that you learn in a few weeks what the rest of us took years! You're on a fast track man!
Jan Didden
Re: DIY gadget man Pedro.
Really? I have a pile of old Japanese transistors removed from amps that test fine...mostly 2SC1885's and such that all measure hfe >700 @ 10mA, but many have the 'carbon' or whatever it is on the legs. So what is the deal with the 'black carbon'? Corrosion? Magic smoke trying to escape? Fill me in...CraigBuckingham said:
I now know that the victims of my curiosity are two power transistors 2SD743 and 2SD414R.
Just ordered them. lets see if they arrive tomorrow. I let you know what is the final result,after the substitution.
the diode is ok, and the resistors seem to be ok too.
lets wait and see.
meanwhile, a old boss of mine asked me to look into his Audionote OTO phono, that hums a bit in the high frequencies and alot with phono. I belive that he didn't hearthed the turntable and the high freq hum comes from the valves, and from his EMIT tweeters from his infinity delta's speakers.
I have the same speakers, and a Audionote too (KIT ONE) and the high freq noise his expected in this kind of tweeters.
I cannot fry this one. It would cost me a months pay!
Just ordered them. lets see if they arrive tomorrow. I let you know what is the final result,after the substitution.
the diode is ok, and the resistors seem to be ok too.
lets wait and see.
meanwhile, a old boss of mine asked me to look into his Audionote OTO phono, that hums a bit in the high frequencies and alot with phono. I belive that he didn't hearthed the turntable and the high freq hum comes from the valves, and from his EMIT tweeters from his infinity delta's speakers.
I have the same speakers, and a Audionote too (KIT ONE) and the high freq noise his expected in this kind of tweeters.
I cannot fry this one. It would cost me a months pay!
HAHAHAHA!! and you can't refuse, because that would get you on your bosses wrong side.. 😛 and you HAVE to fix it, or your boss will doubt your ability, and never ask you to fix things again.... hmm... perhaps thats the best option.. 😀
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