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Speaker pop on shut off Sanyo JCX2900

curtisw99

curtisw99

AK Subscriber
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I’m working through the power supply of my jcx2900k; looking for why the speakers pop.

Question:
I see that 4 of the transistors have black , tarnished legs. Circled in green in the attached photo

I think these are matched pairs, so I have grouped them and found modern matched pairs

I can't find any subs except the matched pair ksc2383/ksa1013 for both applications

NPN 2sc1175 bottom left => ksc2383YTA sub
PNP 2sa659 top left => ksa1013YTA sub

NPN 2sd438 bottom right => ksc2383YTA sub
PNP 2sb560 top right => ksa1013YTA sub

Can someone double check my work?
Should I replace? Whether they’re good or not?
 

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Do you mean complimentary rather than matched? Would need the datasheet posted for them to comment, unless somebody has them in their head.

For a PS rebuild I would replace them, the subs you mention are common subs that likely will work, but do check the voltage and current ratings or post the datasheet.

However, if you are in search of why the speakers pop, power off power on? Randomly? PS transistors are likely only a possible culprit if you have random pops in both channels and all functions.

If you have random pops in everything you are trying to track down perhaps monitor the voltages on the PS, when you hear the pop does a supply voltage twitch or spike?

If you have power off or on pop I would examine Protect more closely to start with.
 
Yes, I meant complimentary, Here's all the data sheets
 

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C2383/A1013 have considerably higher Cob than the transistors you are replacing. It might not be a big deal, but then again, it might.
KSC1815 would be much better for C1175. D438/B560 should be left alone unless proven faulty. They're good devices. Actually, C1175/A659 aren't known for recurring failure, AFAIK.
What is the nature of the "pop" problem? Power on? Power off? Random? Have you separated the preamp from the power amp?
 
tarior said:
C2383/A1013 have considerably higher Cob than the transistors you are replacing. It might not be a big deal, but then again, it might.
KSC1815 would be much better for C1175. D438/B560 should be left alone unless proven faulty. They're good devices. Actually, C1175/A659 aren't known for recurring failure, AFAIK.
What is the nature of the "pop" problem? Power on? Power off? Random? Have you separated the preamp from the power amp?
Click to expand...
It’s a turn off pop
At turn on, the relays work and no pop
So far, i’ve pulled all the diodes and all tested good.
 
The relay isn't opening quickly enough to "beat the pop". Something in the relay drive/protection circuit. I'll make the dangerous assumption that you checked the power supply voltages and they were good.
 
I wouldn't replace those black legged transistors unless they've gone noisy.
I agree there seems to me a problem in the relay/drive circuit.
You could use a 1/4" to 1/8" adaptor headphone plug and plug it in right before turning it off until you find the problem. That should keep the speakers from making the popping noise until you find the problem.
Look closely at the power supply area for any bulging caps, or caps with scorch market on them. I've run into caps that were too close to hot running voltage drop resistors before.
 
tarior said:
The relay isn't opening quickly enough to "beat the pop". Something in the relay drive/protection circuit. I'll make the dangerous assumption that you checked the power supply voltages and they were good.
Click to expand...
Since i’ve read several posts about bad diodes in this unit, I took it apart 1st to check diodes.
This manual has limited voltages listed, but I’ll check what’s available when reassembled.
 
tarior said:
The relay isn't opening quickly enough to "beat the pop". Something in the relay drive/protection circuit. I'll make the dangerous assumption that you checked the power supply voltages and they were good.
Click to expand...
Checked all the voltages in the manuals.
Only transistor voltages are provided.
All those check out.
I’m currently stumped.

I think i’ll get a replacement power switch and see what that does.
I have read this is common
 
tarior said:
That's not the source of your pop problem then.
Replace C431 on the protection board.
Click to expand...
I have one of those caps in the bin, I’ll replace that this week.
Would it be ok to replace the 3 0.47uf non-polar caps (on that same board) with film?
 
I'll take an uneducated guess, if you haven't replaced the relays you can pop the covers off to check the contacts condition.They might be functional enough to make the unit work but allow popping on shut down. As mentioned before sounds like a protection issue.
 
Mr.Heatsink said:
I'll take an uneducated guess, if you haven't replaced the relays you can pop the covers off to check the contacts condition.They might be functional enough to make the unit work but allow popping on shut down. As mentioned before sounds like a protection issue.
Click to expand...
I’ll pull the board and check everything
 
curtisw99 said:
Checked all the voltages in the manuals.
Only transistor voltages are provided.
All those check out.
I’m currently stumped.

I think i’ll get a replacement power switch and see what that does.
I have read this is common
Click to expand...
I have this unit along with pile of Sanyo Plus units. First thing I do is replace the power switches. Many times this resolves unwanted gremlins.
 
lissenup said:
I have this unit along with pile of Sanyo Plus units. First thing I do is replace the power switches. Many times this resolves unwanted gremlins
Click to expand...

curtisw99 said:
I have one of those caps in the bin, I’ll replace that this week.
Would it be ok to replace the 3 0.47uf non-polar caps (on that same board) with film?
Click to expand...
tarior said:
That's not the source of your pop problem then.
Replace C431 on the protection board.
Click to expand...
C431 replaced and still popping.
I’ll report back when I replace the switch.

Would this unit benefit from a triac?
 
Negative on the triac.
Look carefully at the schematic of the protection circuit. This kinda caught me by surprise. There is a set of NC contacts on the power switch that ground the relay drive when the power switch is moved to off. When turning the unit off, be decisive about it. You may have to take that switch apart and clean those contacts with some Brasso or Flitz. Make sure you get all the residue out.
If this works, it will be the first time I've seen fixing a power switch correct a "pop" condition.
 
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