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Nikko QSR-4040 Distortion Questions

A

ArthurFB30

Member
Hello AK users, I'm still working through my Nikko QSR-4040 quadraphonic receiver. I have gone through it; replaced caps, bulbs, cleaned controls twice, etc. However, when I got the unit it had bad bass distortion on both front channels, the rear mimics front in 2CH. I'll do more thorough testing soon. The left channel is distorted a bit worse and pops at idle. I'm curious as to what you all might suspect could cause this behavior. It is not unlike issues I've had with my Pioneer SX-737, or Sanyo Plus-75, where replacing flaky or noisy transistors fixed the problem. I have recorded a video and posted it to YouTube with this link:
. The transistors in question are 2SC945 possibly 'Q' variant, 2SC853 'L' variant, 2SA545, not sure variant, complement to the 845, and finally 2SC1061 for the main AMP transistors. These seem pretty standard parts, shouldn't be too hard to find replacements, but it's always iffy. Any pointers would be greatly appreciated. Thanks

Arthur.
 
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I don't know if it will help, but Hifiengine.com has the 4010 service manual, which also uses the same outputs. Board number is on the board and is 461190B.
If you have a scope, would be a helpful tool.
Besides semiconductors, I'd be looking at low value resistors.
Are there pre out connectors on the back? (there are in the 4010) Clean the switches on the back if any. (pre-main or quad adapter perhaps.) If pre main - run pre to another amp to make sure it is okay.
 
ArthurFB30 said:
Hello AK users, I'm still working through my Nikko QSR-4040 quadraphonic receiver. I have gone through it; replaced caps, bulbs, cleaned controls twice, etc. However, when I got the unit it had bad bass distortion on both front channels, the rear mimics front in 2CH. I'll do more thorough testing soon. The left channel is distorted a bit worse and pops at idle. I'm curious as to what you all might suspect could cause this behavior. It is not unlike issues I've had with my Pioneer SX-737, or Sanyo Plus-75, where replacing flaky or noisy transistors fixed the problem. I have recorded a video and posted it to YouTube with this link:
. The transistors in question are 2SC945 possibly 'Q' variant, 2SC853 'L' variant, 2SA545, not sure variant, complement to the 845, and finally 2SC1061 for the main AMP transistors. These seem pretty standard parts, shouldn't be too hard to find replacements, but it's always iffy. Any pointers would be greatly appreciated. Thanks

Arthur.
Click to expand...

Top Ten Worst Transistors - noisy, failure-prone, whatever... and replacements

I've followed AK advice for several vintage solid state receivers now and the difference in sound, from recapping and from replacing "known-to-be-noisy" small signal transistors to be amazing. While following along with others' threads and trying to help out with "consider replacing these...
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This is where you research if a silicon part, is suspect..
I refer to it quite often.. :)
 
Thank you for the feedback. I have also referred to the transistor thread multiple times, my specific ones aren't there but the numbers are similar so they might have similar traits? I have also looked at the STR-4030 which I thought was similar but has different semiconductors on the amp board. I'll check the 4010 schematic. I could also note I found a burnt resistor on one amp board, but it wasn't open circuit so probably someone's past user error.
 
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