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 Forum index » DIY Hardware and Software » YuSynth
VCO smoke
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okuhtfesa



Joined: Feb 02, 2015
Posts: 5
Location: France

PostPosted: Mon Feb 02, 2015 1:05 pm    Post subject: VCO smoke
Subject description: Yusynth VCO fume
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Hi everybody,

I just finished building my first ever Yusynth module, a VCO and I was soooo excited about it, but... I had fume when I powered it, I think it came from the 78/79L15 ; I first checked power supply polarity but it was fine, then voltage but I have +15/-15 V from my power supply.
I'm quite newby at building totally DIY synth, so if anyone could give me a little tip about what I should check, and what component could have been damage ?

Thank You very much, Cheers
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wackelpeter



Joined: May 05, 2013
Posts: 125
Location: germany
Audio files: 6

PostPosted: Mon Feb 02, 2015 2:16 pm    Post subject: Reply with quote  Mark this post and the followings unread

could it be that you connected them wrong....

i mean they don't have the same pinouts...
whilst on one of them it is in/gnd/out it's on the other gnd/in/out or so...

http://www.electro-tech-online.com/attachments/h18192-jpg.1858/

furhtermore this could be a short afterwards on your board... maybe check again the power rails and ground Connections...

if it's easily possible for you try to place some small fast fuses 100mA to 200mA between your pcb and your psu on both power rails... will maybe prevent more components to disappear in magic smoke... this might be also helpful for checking, testing and possibly Trouble Shooting in further builds...

p.s. as always i would suggest to post pics from both sides of the pcb... maybe someone can spot an error...

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okuhtfesa



Joined: Feb 02, 2015
Posts: 5
Location: France

PostPosted: Tue Feb 03, 2015 3:06 am    Post subject: Reply with quote  Mark this post and the followings unread

Thank you very much for your answer. I think next time I will put some fuse to prevent this kind of magic smoke...

First I now wonder if I did a mistake by connecting ground like I did on the picture ? Then, fume should have came from the electro caps, right ?

Second, I checked the VCO scheme again http://yusynth.net/Modular/Commun/VCO/VCO-sch.gif and here are some points I can't make out :

- What does refer the 1,2 and 3 numbers on the 78L15 and 79L15 scheme ? Because if I refer to the datasheet you linked, I think I reversed the 78 one (in and out switched).
- I wonder if I didn't reverse the trimmer pots, so ; they are from Vishay, T63 and T93 http://www.vishay.com/docs/51026/t93.pdf but I have the same question : do you know what does refer those a, b and c to ?

Thank You again


PSU.png
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psu
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PSU.png



VCO_PCB_componants_2.png
 Description:
VCO PCB components
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VCO_PCB_componants_2.png



VCO_PCB_copper.png
 Description:
VCO PCB copper
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VCO_PCB_copper.png


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PHOBoS



Joined: Jan 14, 2010
Posts: 2263
Location: Moon Base
Audio files: 420

PostPosted: Tue Feb 03, 2015 8:24 am    Post subject: Reply with quote  Mark this post and the followings unread

okuhtfesa wrote:
- What does refer the 1,2 and 3 numbers on the 78L15 and 79L15 scheme ? Because if I refer to the datasheet you linked, I think I reversed the 78 one (in and out switched).
- I wonder if I didn't reverse the trimmer pots, so ; they are from Vishay, T63 and T93 http://www.vishay.com/docs/51026/t93.pdf but I have the same question : do you know what does refer those a, b and c to ?

It looks like you got them inserted correct but the pin numbers in the schematic are wrong for the 79L15 (1 and 3 should be swapped).
As for the trimpots, it looks like it doesn't matter if you'd reversed those (except that for calibration you probably have to turn it the other way).
Which connections a,b,c are is actually in the datasheet you linked to under electrical specifications. Wink
Personally I always start with measuring if all the powerpins for the IC's (not inserted) are connected as they should and if there is no
short between the powerlines. That is before powering it up. Then I power it up and measure the actual voltage on those pins and maybe
some other points. And after that insert IC's and test further.

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yusynth



Joined: Nov 24, 2005
Posts: 1252
Location: France

PostPosted: Sun Feb 08, 2015 1:53 am    Post subject: Reply with quote  Mark this post and the followings unread

Apparently the socket of the LM311 is in reverse position on your PCB. If you powered with LM311 inserted in this orientation you probably burned it.
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okuhtfesa



Joined: Feb 02, 2015
Posts: 5
Location: France

PostPosted: Sun Feb 08, 2015 12:30 pm    Post subject: Reply with quote  Mark this post and the followings unread

Indeed, I reversed the LM331... So stupid, arf. Thank you guys for your kind replies and advices, and of course thank you Yves for those incredible ressources you shared with the community !

Cheers
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