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Old 27th August 2006, 12:05 PM   #21
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I beleive all that switch is a secondary winding voltage selector. They give it a little less rail, for the low impedance setting. I can't say for sure on this particular Yamaha. I think that impedance switch will affect all channels wired on that power transformer.

Do you lose the right channel when the surround DSP is off? in "Direct" or "Stereo" mode? In other words, is the problem nailed down to a line stage or power amp stage problem?
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Old 28th August 2006, 05:01 PM   #22
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Originally posted by mrshow4u
Do you lose the right channel when the surround DSP is off? in "Direct" or "Stereo" mode? In other words, is the problem nailed down to a line stage or power amp stage problem?
Just to clarify the situation so far, with my original surround speakers (6ohm) there was no output from the front right channel apart from the occasional sizzle. (Hence the title of the thread - No output).

However, when I connected some 8ohm speakers for testing purposes I found that I have normal sound from the left front channel and *distorted* sound from the right front channel.

This distortion occurs even when the DSP surround is off and the direct 2 ch stereo setting is used.

With regard to the voltages on the schematics, are these steady voltages that should be present with no signal going through the amp? i.e. No input present?

I look forward to any help anyone can give me.
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Old 28th August 2006, 05:31 PM   #23
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This is sounding more and more like a "dirty" speaker relay. Has that possibility been looked at?
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Old 30th August 2006, 05:19 PM   #24
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Originally posted by mrshow4u
This is sounding more and more like a "dirty" speaker relay. Has that possibility been looked at?

I'm going to look at the relays at the weekend, I'll do a swap with the other channel.

Thanks.
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Old 4th September 2006, 04:04 PM   #25
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Originally posted by grannysmith



I'm going to look at the relays at the weekend, I'll do a swap with the other channel.

Thanks.
OK, so I swapped over the left and right relays and the problem remains on the right.

But now there is no sound from the right speaker for a few seconds after the left speaker comes on. The right speaker fades in and is then distorted.

Any more ideas please?
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Old 4th September 2006, 04:10 PM   #26
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This is sounding not like right and left relays, but more like "Speaker A" and "Speaker B" relay's. .......AND that the right channel is bad on both. Try this: when the Right speaker is distorting, tap the top of the relay and see if the sound improves. If it does, the relay sounds "crusty".
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Old 4th September 2006, 08:45 PM   #27
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This is sounding not like right and left relays, but more like "Speaker A" and "Speaker B" relay's. .......AND that the right channel is bad on both. Try this: when the Right speaker is distorting, tap the top of the relay and see if the sound improves. If it does, the relay sounds "crusty".
But the problem exists on both A and B, could this still be the problem?
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Old 5th September 2006, 01:18 AM   #28
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Grannysmith wrote:
Quote:
But the problem exists on both A and B, could this still be the problem?
It could be the problem, It could be something different too. So the problem is common to speaker A or B. The Right channel is bad. It could be both relays are bad in the Right channel. Speaker relays are often DPDT (double pole, double throw). Left is on one set of contacts, right is on the other set. The volume getting reduced with a distorted sound is the dead on description for an amp with "dirty" relay contacts. It definitely sounds like a poor connection. A poor contact that is current hungry will definitely cause distortion. So, where to look? If there's a headphone jack on the amp, the headphone signal might be pre-relay and run right off of the amp's output points. Listen to headphones phones pre-relay (even while the speakers are playing) Anyway, check solder connections up to the speaker relays. Check solder from the relays to the output terminals. See if tapping the speaker relay (at low or moderate volumes) induces or reduces the distortion heard of the speaker. Make sure the B+/B- (+ and - voltages sometimes called "rails")exist. These voltages should be on the Collectors of the output transistors. Look for +/- 25V~90V somewhere in there. See if tapping stuff can pinpoint the location of the failure. I know there is no wagering allowed, but I'm still thinking relay.
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