Anything that can be done for this ailing Onkyo Tuner?

[DaveC426913]

My boy picked this thing up for a song a few months back. He says it was in great condition.
Onkyo TX-3000
https://www.hifiengine.com/manual_library/onkyo/tx-3000.shtml

Now, a few months on, the right channel has cut out. He says he's checked everything he can think of, including examining the PCB for burned out components (I told him components can easily die without charring, in fact, all they have to do is drift out of required tolerance).

Assuming it's a simple problem:
What steps can he go through to isolate the problem? (I should assume he's made basic checks such as examine the speaker wires for crimps but replace them anyway. But frankly that might be a bad assumption.).

Assuming it's a less simple problem, what steps can he take?

 

[Baluncore]

Get a copy of the circuit diagram, maybe via the link.
You have two channels. Select aux, ground both L&R aux inputs.
Then compare the DC voltages on similar nodes in the two amplifiers.
Look for big DC voltage differences, not minor bias differences.

 

[Vanadium 50]

the right channel has cut out.

I would start by trying to be more descriptive of the problem. Does this mean that with a mono source (e.g. AM) sound comes only out the left speaker? Or does he mean that a stereo source has only a left channel?

Similarly, if he switches speaker cabling does the problem follow the speaker or not? Thus far, no evidence has been presented that the problem is with the receiver and not the speakers.

 

[DaveC426913]

I would start by trying to be more descriptive of the problem. Does this mean that with a mono source (e.g. AM) sound comes only out the left speaker? Or does he mean that a stereo source has only a left channel?

Similarly, if he switches speaker cabling does the problem follow the speaker or not? Thus far, no evidence has been presented that the problem is with the receiver and not the speakers.

Those are all excellent questions, all. Thank you.

 

[DaveE]

Here's my general repair advice:

1) Everyone tends to focus on the electronic parts. They're almost always wasting their time.

2) A careful visual inspection, using a methodical pattern and a magnifying glass, is usually well worth the time spent. This usually requires some disassembly, so maybe a detailed inspection isn't your first step.

3) If it is a failed component it is most likely to be one of the big ones. These tend to be the parts that have the greatest heat or mechanical stress in their lives. Also, some parts just wear out, they are always the electromechanical ones (relays and such).

4) Any connector is my number one suspect. I would typically start just be plugging and unplugging each one. Corrosion or contaminations of the contacts is common. Try to visually inspect the mating surfaces if possible. Look for assembly mistakes at the sockets/pins, like bad crimps, cold solder joints, or wire breakage at the ends (where the mechanical stress is concentrated).

5) If components are mounted in sockets (ICs, relays, etc.), these count as connectors. BTW, this is a clear sign that the equipment is ancient. No one does that anymore, it costs more and is less reliable. The exception is DIY industrial equipment, where people buy modules and plug them together. Anyway, this another common source of problems.

6) Focus on any location where there is mechanical stress. Things like areas the PCB may flex, panel mounted components, connectors, etc. Look for resulting damage like bad solder joints at PCB connectors, etc. If it ever moves or experiences force, it's a prime suspect.

7) Look for signs that someone else tried to fix it. They probably didn't know what they were doing and made it worse. Either that or it's not easily repairable.

8) Purely electronic failures are often related to the power supplies, check them with a DMM. If you can identify common ICs, check their PS pins.

9) If you can't fix it by wiggling things and looking at it carefully, you'll need to get as much documentation as possible. Schematics, and such, are well worth the internet search time.

When I've repaired old test equipment I usually never even turn my oscilloscope on. It is most often a mechanical problem that makes things that should be connected not connected.

 

[Vanadium 50]

I only partially agree. Certainly mechanical connectors should be looked at first. And blowing compressed air through the whole thing to get rid of the dust bunnies buffalo is a good idea. But I don't think I trust 40-year old capacitors all that much more.

 

[Rive]

examining the PCB for burned out components

Well. Good start, but he should check these too:

It's not repair: it's just the basic check before repair.

 

[berkeman]

My boy picked this thing up for a song a few months back. He says it was in great condition.
Onkyo TX-3000
https://www.hifiengine.com/manual_library/onkyo/tx-3000.shtml

I'm guessing that you've logged into that site and downloaded the Service Manual (the login step stopped me). Since this tuner is AC Mains powered, likely with a 2-prong power cord, anybody opening it up and probing the circuitry should be using an Isolation Transformer to power the unit. They are not expensive for small ones, and they will help you avoid getting shocked and can prevent you from vaporizing your oscilloscope ground lead (I haven't done that, since I use Iso transformers, but I do have an EE friend who was in a hurry one time...).

 

[DaveC426913]

Welp, last night, after he did a bit of fiddling, my boy put the cover back on and "blew it up".

So thanks all!

 

[DaveE]

Not a total waste, probably. This is an important lesson in fixing electronics, I think.
"Experience is what you get when you don't get what you wanted."

 

[Tom.G]

...put the cover back on and "blew it up".

Just replace the few resistors that lost their 'Magic Smoke' and fix the darn thing!