Hi , sadly I accidentally spilled a bottle of water ( was on the desk , right next to the amplifier , yes , very good place to keep it ..... ) went into my Amplifier ( music was playing. suddenly died ). It went on the amplifier section. ( output transistors, heatsink. )
I cleaned it , let it dry.
amp does not turn on , power transformer seems ok ( 4 ohm 14 Henry ). Fuse is ok, maybe something else , not even stand by led works.
Measured power transistors show a few ohms, so most likely they might be blown. Until I take it apart and measure.
Output transistors are 2sc3182n / 2sa1265n . Only place I found them , and I have my doubts they are original and not fake.
https://www.adelaida.ro/2sc3182n.html
https://www.adelaida.ro/2sa1265-si-p-140v-10a.html
Bought components from this website before, they were genuine.
*Question is , for testing I think I can use 2sc4468 / 2sa1695.
What better alternatives are ( to use permanently ) instead of the original 2sc3182n / 2sa1265n .
Would 2sc4468 / 2sa1695 work ? they are 20mhz instead of 30, same Ic , power.
250p instead of 220p .
Slightly different Collector-emitter saturation voltage , Collector cut-off current , Emitter cut-off current . Specs I don't really understand.
Datasheets:
2sc3182n
2sc4468
I hope the pre drivers and drivers 2sc3298 / 2sa1306 are alive. Tho I found them too
https://www.adelaida.ro/2sc3298y.html
https://www.adelaida.ro/2sa1306-si-n-160v-1.5a-pioneer.html
* Amplifier is my beloved Pioneer A702r
Service manual down here in attachements.
Weird that no water went on the power supply side. amp just turned off ( died ) won't turn on , not even in stand by at all.
I know water and electronics aren't friends, but tap water , no salt, could cause that much damage !?.
Amp was running pretty high volume, hot ( 27 degrees celsius ambiet temp , yea it's pretty hot here in the summer ) . Temps were around 50c.
So I think I need to take it apart, test the stand by, main transformers separately. Check the output transistors, drivers, pre drivers... etc.
**** I just checked quickly the cable that goes from the main transformer to the amplifier power section +- 55v dc , unplugged, on the amp side it shows 0.5ohm so yea, something is fried.
- " same amp " slightly less power ( a602r ) uses 2sc3281 / 2sa1302 only 4 transistors , two per channel. here on a702r are 8 transistors, 4 per channel but 2sc3182/2sa1265.
are MJL3281A / MJL1302A some kind of replacements for 2sc3281 / 2sa1302 ?. What if I use MJL3281A / MJL1302A instead of the 2sc3182/2sa1265.
- Bruno.
I cleaned it , let it dry.
amp does not turn on , power transformer seems ok ( 4 ohm 14 Henry ). Fuse is ok, maybe something else , not even stand by led works.
Measured power transistors show a few ohms, so most likely they might be blown. Until I take it apart and measure.
Output transistors are 2sc3182n / 2sa1265n . Only place I found them , and I have my doubts they are original and not fake.
https://www.adelaida.ro/2sc3182n.html
https://www.adelaida.ro/2sa1265-si-p-140v-10a.html
Bought components from this website before, they were genuine.
*Question is , for testing I think I can use 2sc4468 / 2sa1695.
What better alternatives are ( to use permanently ) instead of the original 2sc3182n / 2sa1265n .
Would 2sc4468 / 2sa1695 work ? they are 20mhz instead of 30, same Ic , power.
250p instead of 220p .
Slightly different Collector-emitter saturation voltage , Collector cut-off current , Emitter cut-off current . Specs I don't really understand.
Datasheets:
2sc3182n
2sc4468
I hope the pre drivers and drivers 2sc3298 / 2sa1306 are alive. Tho I found them too
https://www.adelaida.ro/2sc3298y.html
https://www.adelaida.ro/2sa1306-si-n-160v-1.5a-pioneer.html
* Amplifier is my beloved Pioneer A702r
Service manual down here in attachements.
Weird that no water went on the power supply side. amp just turned off ( died ) won't turn on , not even in stand by at all.
I know water and electronics aren't friends, but tap water , no salt, could cause that much damage !?.
Amp was running pretty high volume, hot ( 27 degrees celsius ambiet temp , yea it's pretty hot here in the summer ) . Temps were around 50c.
So I think I need to take it apart, test the stand by, main transformers separately. Check the output transistors, drivers, pre drivers... etc.
**** I just checked quickly the cable that goes from the main transformer to the amplifier power section +- 55v dc , unplugged, on the amp side it shows 0.5ohm so yea, something is fried.
- " same amp " slightly less power ( a602r ) uses 2sc3281 / 2sa1302 only 4 transistors , two per channel. here on a702r are 8 transistors, 4 per channel but 2sc3182/2sa1265.
are MJL3281A / MJL1302A some kind of replacements for 2sc3281 / 2sa1302 ?. What if I use MJL3281A / MJL1302A instead of the 2sc3182/2sa1265.
- Bruno.
The most effective replacement is to swap any liquid container near your electronics with an empty space. You're welcome. 😉
Now, seriously, the transistors are (still) in the non-profit range for fakes to make money since the originals are still available and there are alternative trans available for cheap. The transit frequency doesn't have much impact on an audio amplifier if it's that high. being still magnitudes above the used frequency - at least in a solid state amp (class D might be another issue). If there are performance issues, I'd rather check if the pre stage did take any damage which might cause the mis-behaviour.
Now, seriously, the transistors are (still) in the non-profit range for fakes to make money since the originals are still available and there are alternative trans available for cheap. The transit frequency doesn't have much impact on an audio amplifier if it's that high. being still magnitudes above the used frequency - at least in a solid state amp (class D might be another issue). If there are performance issues, I'd rather check if the pre stage did take any damage which might cause the mis-behaviour.
I'm not sure why you're talking about output devices when you have an amp that won't even light up the standby LED. How about fixing that first?
It sounds like there's an always-on housekeeping power supply somewhere. Check the fuse. Check that the rectifier still rectifies, etc. Once you get to the point where you can power up the amp you can start checking the rest.
Tom
It sounds like there's an always-on housekeeping power supply somewhere. Check the fuse. Check that the rectifier still rectifies, etc. Once you get to the point where you can power up the amp you can start checking the rest.
Tom
@brianco it has two fuses, I only saw one ( that was good) , the other one is burnt 3.15A 250V.
All output transistors are dead, I desoldered them, they are either open or short.
No short circuit on the drivers, power supply to the board now does not show short circuit.
Should I try to turn it on with the power amp unplugged first.
Try without output trans?. Output is 3EF as I can see .
All output transistors are dead, I desoldered them, they are either open or short.
No short circuit on the drivers, power supply to the board now does not show short circuit.
Should I try to turn it on with the power amp unplugged first.
Try without output trans?. Output is 3EF as I can see .
Attachments
That's what I'd do if given the option. Get the power supply working. Then work on the amp. Why have a Big Bang test if you can avoid it?
Tom
No, it does not matter (much) since in 99,99% of the amp running, you're not even CLOSE to the maximum rate. Your problem is somewhere else and the 'perfect match' of the power trans is not what keeps your amp failing. Get to the source of the failure and care about what happens before the final stage. If you just swap the final stage trans your amp will blow them again anyway, no matter what you put in there.
Check the power supply first, then the pre stage(s). If you don't fix that, every swapped trans will blow too anyway.
Yes, I've read that. But that does not mean the pre stages are intact!
E: Yes, check the pre stages and check them after desoldering them, then check the final stage trans but if the pre are blown, the final stage will be too!
Amp turns on.
Time to check drivers, if they are ok.
Try it without output transistors at low volume . ? Or solder output transistors.
Time to check drivers, if they are ok.
Try it without output transistors at low volume . ? Or solder output transistors.
Verify operation of the bias stack, and everything up to R347,439 and 441. Disconnect the zobel. Then run off the drivers with a 1K ohm load (and a dim bulb). If there is no sudden jump in current move to a variac and turn it all the way up, slowly, again being on the lookout for any jump in current. Should be full signal, undistorted.
For output transistors use 2SC5200N (Toshiba), 2SC5242 (Fairchild), or NJW0281 (ON) - and the PNPs of course. These are the most direct replacements for C3182. Reconnect the zobel of course. It will NOT be needed running off high fT drivers, and could overload them if hit with high level high frequency.
For output transistors use 2SC5200N (Toshiba), 2SC5242 (Fairchild), or NJW0281 (ON) - and the PNPs of course. These are the most direct replacements for C3182. Reconnect the zobel of course. It will NOT be needed running off high fT drivers, and could overload them if hit with high level high frequency.
@wg_ski Measured each driver , they were fine.
Power transistors are in ( using 2sc4468/ 2sa ) Until I buy something else.
Adjusted idle current at 16mV , how much mA would that be? Seems very low.
Next is dc offset which is 180mV now.
Should I aim for close to 0 as possible or the manual says 80+- 20 mV , .
For transistors when I will order, you recommend getting the originals 2sc3182n or I risk getting fakes ? Maybe is old stock.
Or the 2sc5200N u recommended. ?.
What about MJL3281A / MJL1302A, same 30mhz , stronger transistors?.
Thank you .
Power transistors are in ( using 2sc4468/ 2sa ) Until I buy something else.
Adjusted idle current at 16mV , how much mA would that be? Seems very low.
Next is dc offset which is 180mV now.
Should I aim for close to 0 as possible or the manual says 80+- 20 mV , .
For transistors when I will order, you recommend getting the originals 2sc3182n or I risk getting fakes ? Maybe is old stock.
Or the 2sc5200N u recommended. ?.
What about MJL3281A / MJL1302A, same 30mhz , stronger transistors?.
Thank you .
Attachments
The over current detectors respond to emitter current and output voltage, therefore effectively VCE. With different power trannies, they will still trigger in the same place. That just has to be safe for the new transistors. Of course bigger ones are possible. The C3182 is the baby brother to the C3281. The MJL version is even bigger. With the bigger parts, phase margin could degrade, and high frequency distortion could increase. With EF3 the latter is unlikely. It could actually be better, the C3182’s were less expensive in the day and it very well could have been why they were selected. It turns out the MJL0281 “shrunk” version comes closest to the original Toshiba parts. The N-cased version of the C5200 has the shrunk version of the die, same as the TTC version. It gets even crazier and more confusing than that. The original Toshiba C5200 had two baby brothers - the C5198 and C5242. But when Fairchild made their C5242 they put in their full size version of the C5200. The Toshiba family (which include the ON versions) are pretty much interchangeable as long as you don’t downsize. Parallel banks of course NEED to be the same, and complementary pairs should be used. I have paired L-cased C5200’s with A1302’s because a had a surplus of the PNPs from way back when and never noticed any ill effects. But they are the same size and the amps in question had a distortion floor of about .005%, limited by EM compatibility. It wouldn’t have gotten better if the transistors were perfectly linear.
Old stock 3182’s would be fine if you can get them. Big if, but not as impossible as old stock 3281’s.
Old stock 3182’s would be fine if you can get them. Big if, but not as impossible as old stock 3281’s.