Replacing a Capacitor on an Onkyo HT-R960 A/V Receiver

Question

I have an Onkyo HT-R960 receiver that's been acting very flaky for the past couple of months. I've had to let it warm up for several minutes before being able to use it. I would also have to turn it off and on after it warmed up for it to serve the audio. If I didn't it would sound as click and pop (static) and then go into protective mode (auto-shut off) if turning the volume up too high. Once it warmed up and I turned it off and then back on it would be fine. At the moment it's still clicking and popping, but no amount of warming it up seems to get it to work. I can, however, force it to go into stereo and it plays audio fine on two-channels only. Nonetheless, I've opened it up and it appears the main two capacitors have this tacky black goo on them. The dimple on the top of the capacitors isn't expanded as one can see though. At first I thought this was some sort of insulating material for these capacitors and it was intended. Now I'm not so sure and I've gleaned from several places that it could be leaking from the one or more of the capacitors. Upon further inspection, it does appear to possibly be originating from the capacitors. I won't be able to truly tell unless I remove them. I guess that's next?

My questions are the following:

1. Where to get replacements for these if they should get replaced? From what I can tell this would be an exact replacement: https://www.ebay.com/i/183199809718

However, I've seen much cheaper, but higher voltage versions of these and wonder if those would be Ok: https://www.ebay.com/i/182068444181

2. Should my next step be to remove these and determine if the goo is truly leaking from them? I've replaced capacitors before on other electronics, but I've never heard of a failure with them other than the proverbial dimple expanding to show a failure.

I'm including and image of my capacitors on the main board and a link to the service manual that has schematics for this board. For reference the capacitors are C6901 and C6902 when looking at the manual.

My thanks in advance for any advice.

Service Manual PDF for HT-960

Answer 1

Is it possible that the problem is not on the main supply but smaller Caps on the other sub-channels?

Or is it the combined power draw on all channels? Because why Stereo is ok?

Caps have very complex chemical properties and hard to make very high quality to last 5000 hrs at rated temp. They can sound like a ticking relaxation oscillator then burst the vent .... pfffft.

So far they look ok but that doesn't mean much. Usually old caps can get contamination left off for years. This can trigger leakage current. The pop means a partial voltage breakdown but not a full short.

Like Batteries come in a WIDE range of quality. Stick with Japanese only and these 85'C Gold versions from ELNA are not even their best quality level. The Chinese ones will be much worse quality.

Making good high current Caps is hard.

If the popping it sounds like a slow geiger counter, it could be partial discharge in these caps from tiny leakage of electrolyte thru the membrane internally. Like the "brain" barrier, you can die in a few days from meningitis from a few external bacteria leaking in the brain but not necessarily leak out.

Read how they are etched

Outgassing is the next stage from serious leaks.

Although Rated for 5000 hrs at 85'C , that's 10k hrs at 75'C and 20khrs at 65'C from Arrhenius effects.

I don't know how many amps you have pumped thru these caps but they are designed for high current and heat stresses them faster.

http://www.elna-america.com/ http://www.elna.co.jp/en/capacitor/pdf/catalog_19-20_e.pdf

Answer 2

The "tacky black goo" is normal. It is glue applied to reduce vibrations. The capacitors look fine.

If the capacitors were bad, one of two things would happen:

1. An aggressive liquid would leak out, and cause the wires to corrode. The copper wire would turn green.

2. The tops of the capacitors would pop. Your capacitors have scored lines on top. If the capacitors were bad, the electrolyte would boil and raise the pressure in the capacitor. The can would burst along the scored lines at a relatively low pressure rather than exploding at some (much) higher pressure.

I think you need to look elsewhere for the cause of your problems.