Hobbyist looking to fix a Pioneer SC-1523 receiver with no sound

[jokerwing]

I was gifted a Pioneer SC-1523 receiver that doesn't produce sound by a friend of a friend and I can't find any good resources on troubleshooting the internals of a receiver.
For context I've done a fair bit of hobby electronics work (making speakers, custom lighting projects, and troubleshooting a prior vintage amp), so I don't feel out of my depths here.

What I know and have done so far.
1. Check all the fuses, 9 of them that I can see, are conducting.
2. Power on the receiver and verify that functions seem normal.
2. Factory reset the receiver.
3. Try playing sound from analog input (RCA "CD") and a digital source (a USB flash drive and internet radio).
3a. Tried using the MCACC demo scene too
4. I didn't get sound from any of the three speaker groups on a know good speaker or from the phone output on the front panel
4a. Or from the HDMI group out but it's harder for me to test if that's a known good setup.

BUT
5. The speakers at least partially work. When I turn the speakers all the way up (+12db) I can hear a light hum from the speakers. When turning the volume knob I can hear a little texture in the hum. I can also possibly hear a tiny bit of feedback when I connect / disconnect analog inputs.

This makes me thing the problem isn't with the power or with the amplifier but is somewhere else (but where).

I did a visual inspection looking for blown caps and didn't see any but there's a lot of PCB and I can't see the bottom of several boards.
A number of the connectors are well labelled with their signals but I don't have a good sense of where to start checking for dead signals.

Not sure what I can check next,
Thanks in advanced,
--a newbie

 

[tmtomh]

Pioneer Audio

All Pioneer, all the time.......

audiokarma.org

Lots of knowledgeable folks here at ASR of course - but Audiokarma really caters to detailed repair discussions, and they have a dedicated Pioneer subforum.

 

[JeffS7444]

How's your skills working with surface mount devices? I'd think that all inputs were being converted to digital, and signal routing and processing was all being done on the main logic board.

Power supplies OK?
Any fault causing protection relays to mute all outputs?

If all looks good, but you're getting no sound from any input, I wonder if a multichannel DAC IC has failed.

 

[amirm]

Find the input to the amplifiers and touch them with a finger to see if you can hear hum. If so, then the amplifiers are at least OK.

In general, unless what is wrong is very common and hence a google search shows it, fixing AVRs is very difficult and usually not worth it.

 

[jokerwing]

tmtomh, Thanks to the pointer to the other forum, I'll take a look there.

I'd be comfortable doing surface mounting soulders but I hope it won't come to that

amirm, I appreciate the general advice on repairability of AVRs. I'm a sucker for a fool's errand so I'll stick with it for at least a few more days.

It's been fun to have a look around if nothing else, As a newbie I was surprised how full the case was, as compared to that of more vintage amps. I added a photo and will try to take some better photos tomorrow.

 

[Doodski]

@jokerwing when powering ON can you hear relays making a clicking sound?

 

[jokerwing]

Yep, I hear the relays click when I turn it on and when I change speaker groups. I feel like the speakers are working, because of the hum, but that sound isn't getting to the amps

 

[Doodski]

Yep, I hear the relays click when I turn it on and when I change speaker groups. I feel like the speakers are working, because of the hum, but that sound isn't getting to the amps

Hmmz. Doesn't sound good. If the amp section is in good shape and the relays engaging properly then there is something else causing it to have no sound. I looked for a service manual but found none. With a unit as sophisticated as this servicing it without a service manual would be very difficult even for a trained technician. How old is it?

 

[jokerwing]

Thanks for looking for the service manual, I too spent some time looking earlier without success.

It's 1.5 years old used in a 5.1 sound system that "got some high volume" use (good for the friend, maybe bad for me)

 

[Doodski]

My best suggestion is to take it to a Pioneer service depot and pay the estimate fee to see what is going on. I think that Pioneer home audio was bought out by Onkyo and so you might encounter some depot rebranding or lack of depots.

 

[Doodski]

| Pioneer Electronics USA

www.pioneerelectronics.com

 

[JeffS7444]

At least in the USA, it'll be interesting to see if "Right to repair" has forced manufacturers to be more cooperative in providing service manuals and parts.

Am inclined to think power amps are fine, because if one had failed, I'd think a fuse would blow or protection circuits would be engaged. And it's very unlikely that they'd all fail at once.

In your situation, I might want to focus my attention to those audio ICs contained on the digital board which can actually be sourced on the open market - some can likely be had only as part of factory service, so why waste time there. Large IC at top left of your closeup shot appears a shade darker than the others, but I dunno whether that's significant.

 

[jokerwing]

I found the service manual https://elektrotanya.com/pioneer_sc-75_sc-1528_sc-1523-k_sc-lx57_sm.pdf/download.html

Sadly it might be too late, I had the AC power unplugged which I thought would save me from breaking anything
But when I reconnected the amp power cable (I had unplugged it to see if the unit would still function) the connector sparked and I heard a pop noise after which the unit wouldn't power on.

Still it's been a very fun adventure and I'll have some good photos later