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 Forum index » DIY Hardware and Software » YuSynth
Melted VCO!
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Conboy



Joined: May 01, 2009
Posts: 25
Location: London

PostPosted: Wed Jan 30, 2013 12:35 pm    Post subject: Melted VCO!
Subject description: destroyed VCO - repair advice?
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I accidentally put a large voltage through my Yusynth VCO and burnt it out. The 2 resistors on the power input burnt out. I replaced them but it no longer works at all.

I'm not very good at trouble shooting ;-(

I have replace most of the IC's with no luck. There is power to all the chips on board - I can test that much!

Is it likely I will have destroyed the transistors too?

if anyone can offer any tips I'd be most grateful

thanks
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minisystem



Joined: Nov 16, 2012
Posts: 35
Location: Toronto

PostPosted: Wed Jan 30, 2013 2:48 pm    Post subject: Reply with quote  Mark this post and the followings unread

I shorted 120V AC through my first VCO and blew up my power supply in the process. When I next applied +/-15V the two input resistors went up in smoke, suggesting the high voltage zap had shorted something somewhere?

I gave up and built a new one rather than troubleshoot.
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brock



Joined: May 26, 2011
Posts: 96
Location: Canada

PostPosted: Wed Jan 30, 2013 9:56 pm    Post subject: Reply with quote  Mark this post and the followings unread

You don't say what the voltage was so it's difficult to answer definitively but if you had more than 36V or +/- 18V then you will want to replace all the ICs because even if they are still working they will die an early death. Transistors can be destroyed with high voltage too but the typical bjt will handle 50V or more Vce, Vbe is considerably less. If the voltage exceeded the voltage rating on the caps you might want to replace them too.

I would just assume all the ICs are damaged and replace them all.
If the voltage rating of any cap was exceeded, replace it.
If that doesn't fix things, replace the transistors.
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LFLab



Joined: Dec 17, 2009
Posts: 192
Location: Rosmalen, Netherlands

PostPosted: Thu Jan 31, 2013 1:47 am    Post subject: Reply with quote  Mark this post and the followings unread

+1

Would start with IC's and transistors, and then caps (electrolytic and tantalum, the other stuff is usually ok).
Desolder the lot, get new stuff in, use toothpick to clear holes of solder (heat with iron, touch with toothpick, there you go!).
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yusynth



Joined: Nov 24, 2005
Posts: 1234
Location: France

PostPosted: Sat Feb 02, 2013 11:01 am    Post subject: Reply with quote  Mark this post and the followings unread

Chances are that all the ICs are burned.
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Yves
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Conboy



Joined: May 01, 2009
Posts: 25
Location: London

PostPosted: Mon Feb 04, 2013 4:23 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks Yves

I have swapped all IC's with a known working VCO one by one and still no luck.
Power to all IC's seems fine.
replaced the J112 transistor.

Not a sound - very frustrating!

diodes and caps's next I suppose Sad
?
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yusynth



Joined: Nov 24, 2005
Posts: 1234
Location: France

PostPosted: Mon Feb 04, 2013 1:47 pm    Post subject: Reply with quote  Mark this post and the followings unread

Yes I think so...
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Yves
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