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 Forum index » DIY Hardware and Software » YuSynth
Minimoog filter R1 R2 burning out
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coulis



Joined: Jun 24, 2014
Posts: 3
Location: Liverpool

PostPosted: Tue Feb 17, 2015 10:25 am    Post subject: Minimoog filter R1 R2 burning out Reply with quote  Mark this post and the followings unread

Literally the first module I've made and tried to power up.

The power supply is working fine (Oakley PSU) and the voltage readings are all ok.

R1 and R2 smoke everytime I try to power it up. Replaced them twice now and can't think of anything else to check. Done continuity checks on all the suspect areas but everything seems to be ok.

What would be the best way to diagnose the problem? I assume it is a common issue as two other recent threads are about R1 and R2 burning out on their VCO's.

So close to having my first module working too! Sad
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coulis



Joined: Jun 24, 2014
Posts: 3
Location: Liverpool

PostPosted: Tue Feb 17, 2015 12:37 pm    Post subject: Reply with quote  Mark this post and the followings unread

Been running more tests on the PSU and I'm getting odd results so I've started to enquire about that over at muff wiggler first... I guess must be a problem there Confused
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coulis



Joined: Jun 24, 2014
Posts: 3
Location: Liverpool

PostPosted: Wed Feb 18, 2015 6:19 am    Post subject: Reply with quote  Mark this post and the followings unread

Ok the PSU has been fully tested and everything is working fine (too good infact, I have a very high current which is frying the resistors very quickly!)

Like I say, this is the first module I've built and tried to get working so I'm not sure how to go about troubleshooting to diagnose the problem.

I've checked the board maybe 5 or 6 times now with a continuity test and I've scraped between every suspect contact to make sure there are no shorts. The IC's are definitely the correct orientation, caps are all the right way around.

Are there any standard problems to look out for?

extra info: just finished building the yusynth LFO, plugged that in and it seems to work fine (although no way to test it fully yet). Must be something wrong with the minimoog board I guess.
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The Bad Producer



Joined: Mar 08, 2009
Posts: 282
Location: The Manhole

PostPosted: Wed Feb 18, 2015 7:28 am    Post subject: Reply with quote  Mark this post and the followings unread

R1 and R2 are current limiting resistors on the power rails which act like fuses, as in if there is a problem somewhere with the PCB they will fry. It sounds like you have a short somewhere. Do you have any decent pics of the PCB?
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wackelpeter



Joined: May 05, 2013
Posts: 461
Location: germany
Audio files: 10

PostPosted: Wed Feb 18, 2015 10:39 am    Post subject: Reply with quote  Mark this post and the followings unread

yep... there's a short cut on your moog vcf board... those smoke signs seem familiar to me Wink

p.s. when you checked the board already and didn't found anything maybe look for the frequency pot as it's between gnd and + rail but that would normally only explain the smoking resistor on the positive rail... if either the positive or gnd is wrongly wired on the center leg of the pot....

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