Pioneer sx-525 self inflicted problem

[gtmcgar1]

I have an sx-525 that i was fixing the power switch on for a friend. That went well so I decided to
re cap the power supply board since I had the caps and some time, that didn't go so well I put
one of the 220uF caps in backwards, I know shoot me! Anyway the amp works fine on Aux and measures
40mV on both channels but the tuner section both AM and FM is now bad just slight static. I know these are
tricky to work on but i was wondering if anyone could suggest a path. Any help appreciated, I did
read elsewhere that a board swap is an option but I'm sure someone out there can point me in the right direction. I do have a signal prober hooked up to a small amp that i can use.

 

[zebulon1]

What voltage do you read at +B3 on the Power Supply board?
Are you using a DBT?

 

[petehall347]

i am suspecting you really got things mixed up a bit and you actually put c8 in backwards which should be 470uf and r5 is now toast 560 ohm ..
just a hunch like ...

 

[zebulon1]

Can be fixed without too much fan fair.
I hope
We'll see how Q6 - TA7060P survived.

 

[petehall347]

Can be fixed without too much fan fair.
I hope
We'll see how Q6 - TA7060P survived.

being slow on the uptake here ..where is this q6 you talk about ?
well the the more i look at this the less it makes sense right now ....as you were ...

 

[zebulon1]

The IC for the FM decoder/meter?

 

[petehall347]

The IC for the FM decoder/meter?

found it now .. all of the electros in power supply are grounded so all it would do is short out the positive supply .. b2 and b3 voltages should clinch the deal i would be very surprised if something cooked down the line even if q1 went short . if d3 d4 went short there might well be a bit off humming going on that wasn't mentioned
my bets are on r5 ..

 

[zebulon1]

I concur.

 

[gtmcgar1]

ok here goes with DBT these are the power supply voltages.
B1 45.4v / B2 7.7v / B3 3.6v / BL 3.5v
R5 measures ok but this is a revB board AWR-007B so its a 390ohm R.
The caps were swapped one at a time but some of the values do not match the schematic.
C6 47@16V / C5 220@50 / C7 330@35V / C8 220@25 (SM 470@25) / C9 220@25

thanks for all the inputs so far!

 

[zebulon1]

Did you check the fuse's?
Check all the soldered connections.
Your missing the two important supply voltages, +B2, +B3.
Check for 41.5v DC at the rectifier diodes D3 and D4.
Check leg voltages at Q1, 2SD313 = ON Semi MJE15032G
I think I would go with the scat cap values but at this point whatever close values you have should be fine to get it running. You can fine tune the cap values later.
Not much to the PS, your getting closer.

 

[gtmcgar1]

here goes, checked all the fuses, all ok with dvm.
D3/D4 voltage 37v with DBT, checked e leg of 313 and its only 9v instead of 32v.
I have tip41 and ksd526 available as substitutions would either of these work, all Rs
measure to spec.

thanks again

 

[zebulon1]

Whats the base voltage? If it's near 27v's then the transistor is toast. If not:
Should of had you check the 32v zener, D6. Cathode side. 32.0v's.
A toasted zener could be the issue.
You can use zeners in series. For instance: Two 16v zeners will equal 32v's.
TIP41 should be OK. The MJE's are over kill but margin is good. The TIP41 is adequate.

 

[gtmcgar1]

Some progress thanks to all the help from the experts here!
Did some more voltage checks with DBT after changing the 32v zener for a 33v 1/2w unit, still no luck.
B1 37v / B2 7.9v / B3 3.7v went back and checked all the new caps and found one reading out of spec, C7 changed it out and,...
B1 44.8v / B2 26.4v / B3 11.6v - haven't checked audio or tuner yet that can wait till tomorrow, are these voltages close enough
or do I need to troubleshoot further? Can't thank you guys enough for your time and interest.