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Old 1st November 2010, 07:43 PM   #11
JanErik is offline JanErik  Finland
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Alright, I have updated the schematic ( http://users.abo.fi/jskata/odisseij.pdf ). Almost done tracing it now, soon I can start measuring and comparing to the other channel atleast.
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Old 2nd November 2010, 02:53 PM   #12
Mooly is offline Mooly  United Kingdom
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Comparing is probably the best way forward here. DC conditions should be virtually identical between channels... and if so almost rules out any semiconductor problems. It's not easy tracing out the circuit visually, and without a full and complete 100% accurate circuit it's very difficult to offer anything other than general advice.
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Old 2nd November 2010, 03:40 PM   #13
LAJ is offline LAJ  United States
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Do you have any DC voltage on the output? If not, does it sound like the highs are maybe OK but the lows are gone? Then it is a coupling capacitor. Make a "Y" and feed both channels a signal and check corresponding points between the 2 channels with a scope. How old is the amp? If its 10+ years old, most likely it needs new capacitors. And don't forget, you may have more than one bad. Its not difficult to troubleshoot an amp without a schematic as long as one channel is working.
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Old 2nd November 2010, 04:13 PM   #14
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Default There is the full circuit

There is the full circuit:

Hotfile.com: One click file hosting: ??????? ?-010.pdf

Power amplifier , Preamplifier and Power Supply.

I hope you understand russian. If you have other questions just ask.

Best Regards. Andrey.

EDIT: I just saw that there is a trimmer for the gain on one channel and probably there is the problem.

Last edited by astankov; 2nd November 2010 at 04:20 PM.
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Old 2nd November 2010, 05:47 PM   #15
Mooly is offline Mooly  United Kingdom
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Very interesting indeed...
I agree, presets definitely could be dicky and just also just change those electrolytics anyway.

What's so unusual is to see an amp of this configuration set up in inverting mode...
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Old 3rd November 2010, 11:38 AM   #16
JanErik is offline JanErik  Finland
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Quote:
Originally Posted by astankov View Post
There is the full circuit:

Hotfile.com: One click file hosting: ??????? ?-010.pdf

Power amplifier , Preamplifier and Power Supply.

I hope you understand russian. If you have other questions just ask.

Best Regards. Andrey.

EDIT: I just saw that there is a trimmer for the gain on one channel and probably there is the problem.
Thank you very much! This is very hard-to-find info, did not even believe this was any longer in existance except for in some Ukranian dumpster! Do you think it is OK if I put it on my own webspace so others can download it easier without this one-minute wait and captcha?

I know a bit Russian but not many technical terms...
I have seen there is a tiny trimmer in the middle of the board but thought it had something to do with the clipping indicator. Did try to fiddle with it with no noticable change. Not yet traced it in my diagram. The other two trimmers set quiescent current and output offset.
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Old 3rd November 2010, 03:55 PM   #17
JanErik is offline JanErik  Finland
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Found some pics and data now as I got the model number clear;
Стереофонический усилитель ''Одиссей У-010 стерео''.

Incredible that it is only specced to 50 W @ 8 ohm, still weighs 16 kg. If I understand correctly, it is 0.05% THD.

The same schematic is also found here: http://mexan1k.info/info/images/6/62...pasport_19.jpg

Some manuals:
http://mexan1k.info/info/index.php/%D0%9E%D0%B4%D0%B8%D1%81%D1%81%D0%B5%D0%B9_%D0%A3-010_%D1%81%D1%82%D0%B5%D1%80%D0%B5%D0%BE_(%D0%BF%D 0%B0%D1%81%D0%BF%D0%BE%D1%80%D1%82)
Sorry the cyrillic letters don't work on my computer but the links seem to work.

Last edited by JanErik; 3rd November 2010 at 03:57 PM.
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Old 3rd November 2010, 03:56 PM   #18
LAJ is offline LAJ  United States
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Most stuff here in the States is Chinese now and I can tell you Russian is easier to read than Chinese. I doubt the trimmer is the problem. Be careful that its not the bias pot. You don't want to blow up your output stage. And I think the reason its inverting is so if the output gets coupled back to the input, it doesn't self destruct.
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Old 3rd November 2010, 03:59 PM   #19
JanErik is offline JanErik  Finland
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If you look closely, the two channels are mirrored, look at the LTP for example.

Or maybe not, the supply voltage is just drawn from another direction.

Should I assume all voltages in the schematic are relative to ground?

Last edited by JanErik; 3rd November 2010 at 04:09 PM.
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Old 3rd November 2010, 05:28 PM   #20
JanErik is offline JanErik  Finland
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Quote:
Originally Posted by astankov View Post
EDIT: I just saw that there is a trimmer for the gain on one channel and probably there is the problem.
Is that the one marked "Regulkrdva usilenija"? It is on the other channel than the one I have suspected to be too weak, could that one be too strong?
Why would they make such, shouldn't both channels have inherently the same gain?
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