Dad's old "new" Pioneer SX-535 power amp board noisy transistors?

[jpreza]

Good afternoon everyone!

I'm visiting dad in Florida for the next week. While I'm down here, I decided to service his dear old Pioneer SX-535. It was making the old "popcorn" sound no matter what output was selected.

I looked at the power amp board and saw the dreaded 2SA726s (Q1 through Q4). Those have been replaced with KSA992s. I've also replaced ALL the capacitors on the power amp board. The "popcorn" sound went away. Beautiful sound coming out now!

That said, I haven't replaced the 2SC1318s (Q5 through Q8) or the 2SA720a (Q9 and Q10). When I turn the balance to either L or R channel, I hear a very faint "pop" regardless of the selected output (AM, FM, AUX, or PHONO). I'm assuming it's one of those transistors. I don't have any KSC2383s on hand to replace the 2SC1318s, and I hope they arrive in time before I leave.

What's the recommendation for the 2SA720s for this receiver? Is it better to get the KSA1220s or KSA1013s?

Also, am I going down the right path regarding the "pop" sound I'm hearing?

TIA....JP

 

[larryderouin]

sx-535 links:
https://www.audiokarma.org/forums/index.php?threads/pioneer-sx-535-noisy-transistors.809085/

https://www.audiokarma.org/forums/index.php?threads/my-sx-535-parts-list.711267/#post-9556288

https://www.audiokarma.org/forums/i...ok-out-my-pioneer-sx-535.705085/#post-9544279
The pop could be further down the line, either a cap (change all the sky blue SANYO caps smaller than 5.0uf), they're on par with the 725/726 transistors for being crap, or a transistor.

These 3 threads will give you the best shot at parts. 2SA720's

SX-535 ,AWH-035,Q9,2SA720,,,,512-KSA1013YTA
SX-535 ,AWH-035,Q10,2SA720,,,,512-KSA1013YTA

2sc1312's and 1344's use KSC1845's.

 

[jpreza]

sx-535 links:
https://www.audiokarma.org/forums/index.php?threads/pioneer-sx-535-noisy-transistors.809085/

https://www.audiokarma.org/forums/index.php?threads/my-sx-535-parts-list.711267/#post-9556288

https://www.audiokarma.org/forums/i...ok-out-my-pioneer-sx-535.705085/#post-9544279
The pop could be further down the line, either a cap (change all the sky blue SANYO caps smaller than 5.0uf), they're on par with the 725/726 transistors for being crap, or a transistor.

These 3 threads will give you the best shot at parts. 2SA720's

SX-535 ,AWH-035,Q9,2SA720,,,,512-KSA1013YTA
SX-535 ,AWH-035,Q10,2SA720,,,,512-KSA1013YTA

2sc1312's and 1344's use KSC1845's.

Good news! The 2383s arrived today but not the 1013s. They should be arriving by Thursday along with the Nichicon UKL caps to replace all the baby blue Sanyo caps smaller than 5.0uF.

I did replace the 2383s in the power amp board (Q5 through Q8). After doing that, the "pop" that I was hearing when the balance knob was all the way to L or R channel is GONE! Woohoo!!

So I think what I have left is:

1. Replace the Sanyo caps all around the tuner/control boards
2. Replace the two 2SC1344s in the control board with KSC1845s
3. Replace the 2SA720s with the KSA1013s in the power amp board - the other trannys and caps have been replaced
4. Replace all caps in the power supply board
5. Replace the one 2SC945 transistor in the power supply board

I'm debating #5 because after reading the service manual, you are supposed to do the FM adjustment if you replace ANY of the transistors. I don't have an FM signal generator. So my question is should I replace the transistor or leave it in with the potential that it is a time bomb?

TIA...Joe