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Old 25th August 2010, 11:03 AM   #11
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i got suv 40 and suv 60 if this is any help to you ... e mail me if you like to have them
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SERVICE ΕΝΙΣΧΥΤΩΝ ΚΑΙ ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr
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Old 26th August 2010, 11:55 PM   #12
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Thank you once again, Sakis.
It is helpful guys like you that make this Forum absolutely the best.
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Old 26th January 2015, 03:03 PM   #13
poolz50 is offline poolz50  United Kingdom
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Sorry to bump a old thread but...

I am also trying to repair a SU-V50 AA amp.

A house move drop mean all the connectors on the back got snapped off. I replaced this with some new studs in a new mounting plate but now it won't engage, there is no click. I am worried I have turned it on without a load over the speaker connectors whilst making this repair.

So - did anyone get the complete schematics?

Would really appreciate them if so.

Best wishes

Dan
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Old 26th January 2015, 04:20 PM   #14
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Quote:
Originally Posted by poolz50 View Post
So - did anyone get the complete schematics?
Well, I didn't but solid state amplifiers don't need a load to keep them stable - that's a bit of advice for the "toobs" fans.

As you're having a problem, are you sure you didn't actually short the connectors and try to use it in that condition? Unfortunately, this is not an easy design or series of designs to understand, let alone troubleshoot so don't hold your breath in hope of a simple 1-2-3 step fix unless you have simply gotten the output rewiring mixed up.

Note that there is an auto-sensing 4/8 ohm load switching controller involved in the SUV50 and that must be working correctly (IIRC) to enable correct power-up. The power-up delay is not the usual output relay though, its a delay on applying power to the current dumping amplifiers - after and only if the class A amplifier is stabilized. If that is not occurring, you may have caused more serious problems and this could be beyond the abilities and parts resources of most DIYs.

This is not a class AB amp. It's a close cousin of class S or Aubrey Sandman's feed-forward error correcting design from around 1979, hence the somewhat complex and delicate arrangement to get stable class A operation before connecting the class B power amplifiers. Quad 405,306,606 etc series of amplifiers have a similar basic operating principle but Technics' is a much more sophisticated and complex approach - later versions were simplified by using proprietary ICs and power modules - mostly unobtanium now.
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Old 26th January 2015, 04:41 PM   #15
poolz50 is offline poolz50  United Kingdom
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Quote:
Originally Posted by Ian Finch View Post
Well, I didn't but solid state amplifiers don't need a load to keep them stable - that's a bit of advice for the "toobs" fans.

As you're having a problem, are you sure you didn't actually short the connectors and try to use it in that condition? Unfortunately, this is not an easy design or series of designs to understand, let alone troubleshoot so don't hold your breath in hope of a simple 1-2-3 step fix unless you have simply gotten the output rewiring mixed up.

Note that there is an auto-sensing 4/8 ohm load switching controller involved in the SUV50 and that must be working correctly (IIRC) to enable correct power-up. The power-up delay is not the usual output relay though, its a delay on applying power to the current dumping amplifiers - after and only if the class A amplifier is stabilized. If that is not occurring, you may have caused more serious problems and this could be beyond the abilities and parts resources of most DIYs.

This is not a class AB amp. It's a close cousin of class S or Aubrey Sandman's feed-forward error correcting design from around 1979, hence the somewhat complex and delicate arrangement to get stable class A operation before connecting the class B power amplifiers. Quad 405,306,606 etc series of amplifiers have a similar basic operating principle but Technics' is a much more sophisticated and complex approach - later versions were simplified by using proprietary ICs and power modules - mostly unobtanium now.


Hi Ian,

Thanks for the reply. I am pretty sure I did not make any mistakes like wrong re-wiring. In reality the de-bugging was a little more complex. The system worked for a while, then stopped. I opened it up and noticed that it jumped back to life when wiggling one of the components. That turned out to be a brittle solder bond, a repair of which bought it back to life again.

Then, for ages it kept dropping a channel. It was strange as it seemed to change which channel it was dropping, even if I switched to the remote ring.

All in all I got a bit annoyed and shelved it until now. I want to have one last attempt but now it wont even click on at all!

I don't suppose you have a couple of obvious voltage checks I could do. I saw in another thread you (I think) recommended checking certain pins.

I appreciate you don't want to get involved in a complex remote-fix so I understand if not.

all the best

dan
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Old 27th January 2015, 08:42 AM   #16
poolz50 is offline poolz50  United Kingdom
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Dear Ian,

After some investigation it appears the current drive LED comes on ( I assume its happy) but the relay fails to click. a light tap on it makes it click and the unit comes back on! So - I think the relay is past its best.

The next problem to solve is that the RHS channel is dead. That could be my wiring for sure- I don't think the relay controls the channels independently.

For you - I found the service manual, which is in my drop box:

https://www.dropbox.com/sh/eoglkw2ao...q0BmW9hLa?dl=0


Thanks

Dan
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