Pioneer SX-525 blows right channel fuse

[mark126]

Hi,

I'm new here and will be reviewing the archive to see if I can learn anything related to my problem. But, in the mean time, maybe y'all can offer some suggestions.

I picked up a free Pioneer SX-525. The PO said the left channel didn't work, but the right did. Well, here is what I have found out so far.

The right protection circuit fuse was blown. I replaced it and it blew right away (within a second of power up, with a loud hum from the speaker). I can tune both AM and FM (though not very well) and hear sound from both channels. Quieter on the right (no fuse). What is the function of the protection fuse?

It's also missing either the tuning knob or function selector knob (the PO said she found one, but didn't say which). The right half of the display is dark (not blue). What is a good source of replacement bulbs and knobs? The AM light is not very bright. The vertical tuning indicator is not illuminated (is it supposed to be?).

What I have done so far is just spray some Rat Shack contact cleaner/lubricant on all of the switches and dials, and the tuning mechanism. I realize now that that product is not looked upon highly here. Hope I did not make anything worse.

I have a VOM. I do not have a manual or schematic yet -- I thought I would try to get an idea of how bad off it is before investing in it.

I'm planning on using this receiver in a small 10'x10' room with a pair of KEF C-30s I found at a pawn shop. Think it will be a good match?

Thanks in advance from a newbie eager to learn,

Mark LaPlante
Huntsville, AL

 

[EchoWars]

Welcome to the site!!

Sounds like the Pioneer blew the output devices on at least one channel. AFAIK, Pioneer does not fuse the protection circuit per-se, what makes you think this fuse is part of the prot circuit? Yes, technically ALL fuses are a 'protection circuit' in and of themselves, but generally a protection circuit is designed to prevent DC at the output terminals, and to reduce output stage drive when current rises too much. I'm not terribly familiar with the specific topology of the 525, but many of these earlier Pioneer's were capacitor-coupled to the output (if so, DC isn't going to be the problem, fried components are).

Still, the amp needs surgery. Obviously there are blown devices on at least the one channel, and it takes a bit of experiance to track 'em down sometimes.

No magic wand or rabbit to pull out of a hat here...the patient needs professional help.

 

[mark126]

The fuse is accessible from the back panel beneath the word "PROTECTION". There is a fuse for RIGHT and a fuse for LEFT.

But, I may have jumped to conclusions in thinking that this meant it was part of the protection circuit. :headscrat

Every professional had to start somewhere. I figure the worst case is I will end up with a free receiver that (still) doesn't work. And I might learn something along the way.

Thanks,

Mark

 

[EchoWars]

Hmmm...then perhaps the fuses are on the voltage supply rails for the separate channels...like I said, not real familiar with that specific model.

If it's blowing fuses, something's shorted. Probably the output devices, but that's just a guess based on past experiance with a lotta blown amps.

If you want to tackle this, get the manual first, otherwise you're simply wasting your time.

Best of luck!!

EW

 

[in with the old]

That is very good advice. If you want to learn how then one of the best ways is the proper service manual with schematic. For a few bucks you might end up far ahead from now. Have patience when troubleshooting and ask questions when you need advice.

 

[mark126]

Source for service manual?

I sent an email to stereomanuals.com a few days ago, but it seems the owner of that site may be busy attending to his sick mom.

Anyone have any scans or know any other sources? Looking for schematic, service manual, and user manual for Pioneer SX-525.

Thanks,

Mark

 

[EchoWars]

If you wait a month or two, he'll respond.

http://www.agtannenbaum.com/p_cat.html#PIONEER

 

[dsk]

I gots the schematic.

 

[mark126]

I ordered a schematic from ebay, but I would imagine it will take a week or more to get here. If you have a scan to get me started, it would help.

Mark

 

[dsk]

I tried, but I'm having a scanner problem. I'll try to work through it.