Pioneer SX-525 - No sound at all

[touche112]

Hey all!

I picked up a Pioneer SX-525 in a salvage shop for a measly $5. Got it home today, powered it up, and it glows like the first day out of the box. But I have no sound!

So, I replaced the left and right "protection" fuses, found an unwrapped yellow wire that went to one of the large caps (rewound that), and did some general cleanup with a toothbrush and some compressed air. Can't really find anything else out of the ordinary.

Before I go ahead with a full recap, any advice on where to look? And while I'm at it, I know I don't need to replace mylar or ceramic caps, but what about "oil paper" caps? Should I replace those with modern elecrolytics?

 

[elvi]

Sound from headphones? Attach a wire to the 300 ohm antenna points, and can you "see" FM stations tune in?
No protection relay on this one (to hear click on)

were the fuses blown? (Were they the correct value?)
Its either very dirty switches, or something more sinister(Hence the blown fuses).
Hifiengine.com has a manual listed.

 

[mbz]

Sort out your audio problems before the recap. Check power supply voltages since both channels down.

 

[touche112]

Okay so an update. I replaced a cracked diode on the main amp board, replaced the smaller power supply board as the PCB was cracked (AWR-007), and replaced the L/R channel protection fuses on the rear.

Inside the unit behind the AC/DC transformer, there are three fuses that are wrapped in plastic. One of those is blown. It's marked 500V 3A. As I do not have any 500V fuses handy, I checked the service manual and I can't see any notes on the voltage of the fuses, so I replaced it with a 250V 3A, and it immediately blew.

Here is the fuse in question:

The fuse is wired to the blue cable coming from the transformer on one end. Other end I haven't traced yet.

 

[touche112]

Hmmm, the blue wire goes to the lamps.

 

[mbz]

The blue wire winding also feed the main amp (pin 18) and the power supply (pin AC5).
Maybe one of the globes is shorting on the case?? Check resistance to chassis at
fuse (downstream side) Check these wires and solder connection

 

[touche112]

Got that fuse sorted out, there were two bridged solder points on the main amp board.

Checked the PSU board. I have 12v/24v out of B2/B3, and 51v out of B1. Seems good there.

Must be something up with the main amp board? The big 3300ua cap has a solid 51v reading. The smaller 2200ua caps have no voltage. I replaced those and still no voltage on either.

Also, found R31 on main amp that had a leg not soldered in... resoldered it and it literally exploded when I powered on the amp so that's cool.