Onkyo M 508 Capacitor goo

[jtee1340]

First of all I am new to this forum and already it has helped me with this issue. Got the downloadable service manual for this amp from a post search. Thanks for the info.
I moved the amp the other day and noticed a brown hard goo under on the bottom cover. I researched the net for possible problems and found out about the 10,000 uf caps that are a known problem. I opened the amp and that is the area where the problem seems to be.
The amp is working ok, but I don't like when my stuff is not right.
Lookin around for the caps has taught me these caps are not real easy or cheap to come by.
Has anyone done this repair? Where did you get your caps? Costs?
What should I know in advance before changing them out? (ESD and normal percautions I am aware of)
Onkyo USA has the caps for about $300.00 for the 8. Different part number so I suspect they upgraded the part for this issue.
Seems like a straight forward job, but I like to ask others that have done something for advise to make a job smooth if possible.
Thanks in advance for any info.
J.T. Stanton

 

[K-amps]

JT,

Any cap of similar dimensions will work. As you know to look for the ESR/ Cap/ voltage rating. Chances are for the same size, newer caps will be higher capacitance or voltage rated, this is fine as long as it does not exceed 20% of the capacitance because then you may be taxing other components.

I would not pay $300 for 8 standard 10,000uF caps....

 

[Jan Dupont]

As I recall, the PSU caps in the M 508 are known to have a hard time, and even blow up frequently due to the low working voltage of the original caps.....

As k-amps write: find some with a working voltage 20% over the supply
As I can see in the service manual, the M 508 has a rail of 74.5 Volt DC and 80V caps

 

[Stocker]

to make the answer less complicated: You can likely replace the capacitors with some 10,000uF 100V capacitors from any reputable manufacturer and be just fine. Shop distributors for price.

 

[B Cullingford]

Not as bad as some amps I fixed in the past (affectionally called Flame Linears by some of my fellow techs) in which the manufacturer assumed that cap voltage ratings were conservative and used higher rail voltages than cap V rating!! (if memory serves 75V caps and 80V PS)

 

[Jan Dupont]

B Cullingford:
Is that the same "Linear" company that assumed that an output stage with max capacity of 250W easily could deliver an output of 200W for years after years

 

[B Cullingford]

that would be them - oh how I loved replacing PCB traces with wire!

 

[K-amps]

And is that the same guy who rates his new toys as capable of driving 2400 watts into 1 ohm with BJT's that have less total dissipation than what they are driving at 1 ohm?

 

[Jan Dupont]

It sounds very possible

 

[thomas997]

Just to be sure, the hard goo is not between the capacitors and the board is it?

Or is it actually leaking out of them?

because some manufactureres use glue for the large caps on the board.

 

[jtee1340]

The substance is a hard brown and partially black stuff that has dripped down on the lower cover vent slots. It actually fell through and got on the stereo stand under the amp.
I did not see any oozing out of the capacitors themselves, but it did come from that area in the amp.
If one of these caps were totally blown would the amp still work?
The amp was used in my home theater setup for a while powering my Infinity Reference Standard 3b speakers. I did have a short time when the amp would go into overload but it would come back if I turned it off and back on.

 

[anatech]

If I remember correctly, taking the originals out is a real pain. Non-standard leads is why the price is so high. If you can use something else, then do so. Mounting them may need some re-thinking.
The amp would still work as the caps tend to go open. Shut downs would be expected in that case.

-Chris

 

[BrianDonegan]

If they use a non-standard mount, perhaps you could photograph and measure the pins and caps and post more infor here. I'm sure someone can help you pick some replacements that would save you a couple hundred bucks off the Onkyo price.

 

[K-amps]

Dont be afraid to drill a few holes into the bottom of the PCB...

Disclaimer: I am assuming you know what you are doing.