Problem with Onkyo A-8500 (Integra) Amplifier

- P
- paninocolsalame
  
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posted
17 years ago

Sun, Dec 24, 2006 7:31 AM

Hello,

After 19 years playing music very well, my Onkyo A-8500 (Integra line) amplifier has problems especially when it's cold (just powered-on). The speakers level is low and there is distortion. Switching from the Speakers pair A to the B and back to A can lead to a different result (better or worse output).

I think that the problem could be caused by a relay that is used to switch the speakers pair that need to be replaced. The series resistance of the bad contatcs that is added to the load can be the cause of the distorsion. I see two relays in the middle of the amplifier (they seem to be protected from dust/humidity) and a small one on a hardly accessible little board related to speaker pair switching (!). The last one may be not so protected from external agents (transparent cover).

So, the questions:

- Have you the schematic / service manual of the Onkyo A-8500?

- Do you agree with me when I blame the small relay?

Best Regards and MERRY CHRISTMAS

Panino

- A
- Arfa Daily
  
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posted
17 years ago

Sun, Dec 24, 2006 12:36 PM

You may well be on the right track with suspecting a relay - but I would suggest that it's going to be one of the big ones. The small one will just be for signal switching, possibly to switch tape monitoring or something like that. The big relays will be the speaker protect / select relays, and it is quite common for them to get bad contacts giving the symptoms you describe, on all sorts of makes and models. Very often, if you take the amp's cover off when it is bad, then give the relay covers a sharp tap with the butt end of a screwdriver, it will come back right. Many speaker relays have snap-on covers, which come off easily when you slide a scalpel blade in the crack between the cover and base, and twist. It is quite unusual for the contacts to be burnt and pitted. Usually, they are just sooty, and all they need is a piece of cardboard, soaked in isopropyl alcohol, drawn between them.

Arfa

- N
- Nate Scharff
  
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posted
17 years ago

Mon, Dec 25, 2006 5:31 PM

It sounds like you are using 4 ohm speakers. Most amplifiers are only rated for 8 ohm minimum impedence.

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- Leonard Caillouet
  
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posted
17 years ago

Mon, Dec 25, 2006 5:41 PM

Using 4 ohm speakers on an amp rated for 8 ohms would not cause low, distorted sound unless something was damaged by drawing too much current from the amp. Since the system worked fine for a long time, the symtom described may be just what he suggested, a relay problem.

Leonard

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