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 Forum index » DIY Hardware and Software » Rob Hordijk DIY Designs
Benjolin troubleshooting (doing ...nothing at all..)
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okelk



Joined: May 08, 2014
Posts: 71
Location: Vienna

PostPosted: Sat Mar 07, 2015 8:35 am    Post subject: Benjolin troubleshooting (doing ...nothing at all..)
Subject description: where to start?
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so I build a benjolin yesterday.

It's doing nothing at all and so I don't know what to search for.

I already checked the power in the ic sockets, and all the chips are getting +/-9v to gnd.
If it would have some weard behavior, I I may have an Idea what to search for, but it's doing nothing at all! Sad

Any ideas where to start troubleshooting?
help would be very much apprechiated.
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elmegil



Joined: Mar 20, 2012
Posts: 2177
Location: Chicago
Audio files: 16

PostPosted: Sat Mar 07, 2015 8:46 pm    Post subject: Reply with quote  Mark this post and the followings unread

Always start with the power, but you seem to have recognized that. Have you checked the power with the chips inserted as well? It's not clear from what you've said. If you have one bad chip dragging the rails down, it'll kill the whole thing.

From there I would start with the oscillators. Do you get anything at T1/P1/T2/P2?
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okelk



Joined: May 08, 2014
Posts: 71
Location: Vienna

PostPosted: Sun Mar 08, 2015 8:04 am    Post subject: Reply with quote  Mark this post and the followings unread

Now I checked it also with the chips inserted.
it was fine first, then suddenly went up to 12v on the positive rail. (the 7809 broke. I replaced it.)
Also I realized that the TL074 left from the ssm2164 (U1, I think ?) and the ssm2164 got quite warm. The TL074 also gets warm without the 2164 installed.

So I assume that for some reason ether the tl074 and maybe also the 2164 are sucking too much power on the possitive rail... Sad

...any Ideas where to start searching?
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elmegil



Joined: Mar 20, 2012
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PostPosted: Sun Mar 08, 2015 10:21 am    Post subject: Reply with quote  Mark this post and the followings unread

With the power off, verify the connections match the schematic, and review the board carefully (possibly with a magnifying glass) in those areas to look for shorts.
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lunaire



Joined: Jan 23, 2009
Posts: 19
Location: Sao Paulo

PostPosted: Sat Mar 14, 2015 2:06 pm    Post subject: Reply with quote  Mark this post and the followings unread

Im trying to troubleshoot a benjolin from a friend and I cannot find any errors in his soldering, all points are conductive, but the sound just seems not be exactly correct and one of the 9v batteries always gets VERY hot. Any ideas why is it getting so warm? OR how can i compare the sound? Any demos of basic benjolin available? Cause I guess those eurorack/macumbista might just sound a little different?
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elmegil



Joined: Mar 20, 2012
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PostPosted: Sat Mar 14, 2015 2:30 pm    Post subject: Reply with quote  Mark this post and the followings unread

a 9V battery getting very hot means you're drawing a LOT of current.

I think you'd need to measure and compare various points in the circuit to see what was different, or whether there was a chip or other component that's also getting hot.
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soundworker



Joined: May 31, 2013
Posts: 21
Location: Germany
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PostPosted: Sun Mar 15, 2015 4:34 am    Post subject: Reply with quote  Mark this post and the followings unread

If there was +12V / -9V on the power rail of Benjolin the 4021 may be killed. This CMOS IC run max at +-9V, but over it died.
Replace it an try it again; better take it away and test first output of both VCO (at output connector) then filter and at last insert 4021 to see rungler signal at IC6 pin 14.

Best
willi
KlangbauKöln
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L´Andratté



Joined: Sep 23, 2012
Posts: 150
Location: Hamburg, Germany
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PostPosted: Sun Mar 15, 2015 12:34 pm    Post subject: Reply with quote  Mark this post and the followings unread

sorry no time atm to think about your problem
but his could be part of the issue
http://www.milton.arachsys.com/nj71/forums.html?menu=2&submenu=2&subsubmenu=3
good luck
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