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IC Chip short circuit repercussions
Old 19th December 2019
  #1
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Thisiscobras's Avatar
IC Chip short circuit repercussions

Long story short when testing some IC chips in circuit and powered on I must have touched a couple legs at once causing a chip to short. My quick question, is this damage usually contained just to the chip itself or does it spread to surrounding resistors and capacitors etc.? No smoke or burnt components or anything like that.
Old 19th December 2019
  #2
Depends what the pins that you shroted out were connected to. Some chips have pins that aren't used at all and if the supply voltage pin wasn't involved it may be ok. Power it up and see what happens. If you've already damaged it you're not risking it any further and if the short was momentary you might have got away with it although the danger is that the damage could be so microscopic that it works ok for a while but dies in future - no way of knowing until it dies unfortunately unless you have an electron microscope.
Old 19th December 2019
  #3
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Quote:
Originally Posted by mrfantastic View Post
Depends what the pins that you shroted out were connected to. Some chips have pins that aren't used at all and if the supply voltage pin wasn't involved it may be ok. Power it up and see what happens. If you've already damaged it you're not risking it any further and if the short was momentary you might have got away with it although the danger is that the damage could be so microscopic that it works ok for a while but dies in future - no way of knowing until it dies unfortunately unless you have an electron microscope.
Thanks much for your reply. Here's the other half of the story. I'm pretty scared at this point:

I've been trying to fix what was a very small issue on my beloved SCI Prophet 600 for the past month. Simply 1 Oscillator was out of tune. Everything else worked flawlessly. I was methodically replacing parts and testing after each. All was well as I was slowly tracking down the exact problem. That was until last night when I got the bright idea to use my multimeter to try and check/compare IC chip voltages between a good voice and the one I was having a problem with. I checked the direct voice IC chips 4016 (quad analog) and 4053 (multiplexer) for 2 voices as well as 2 small op amp chips in the S/H section. I grounded the negative probe on the metal chassis and used the positive to check the legs of the ICs. Apparently I'm an idiot for doing this and/or I accidentally caught 2 legs at once and hopefully just shorted a chip only. All was well minus the 1 Oscillator prior to this and now when I power on immediately I hear a loud screeching/white noise followed by what sounds like an Orbital CD played backwards and not in a good way. Keys respond as does the membrane panel and display. No matter what I do there is just noise in the background and all sorts of digital vomit. I'm really hoping I simply just fried one of the chips I tested and that's it. I'm in the process of putting together an order to replace the 6 total chips I touched. I'm really hoping just to get a little peace of mind in the meantime that this is likely all I did and that whatever happened didn't spread down the line to other places.
Old 19th December 2019
  #4
CMOS logic chips are cheap, I get them from Jameco for about a quarter. They have no input protection like many opamps,. They are CMOS and static sensitive. Just change them, they are cheap. Machined sockets will assist in future errors.
Old 19th December 2019
  #5
Quote:
Originally Posted by Thisiscobras View Post
Thanks much for your reply. Here's the other half of the story. I'm pretty scared at this point:

I've been trying to fix what was a very small issue on my beloved SCI Prophet 600 for the past month. Simply 1 Oscillator was out of tune. Everything else worked flawlessly. I was methodically replacing parts and testing after each. All was well as I was slowly tracking down the exact problem. That was until last night when I got the bright idea to use my multimeter to try and check/compare IC chip voltages between a good voice and the one I was having a problem with. I checked the direct voice IC chips 4016 (quad analog) and 4053 (multiplexer) for 2 voices as well as 2 small op amp chips in the S/H section. I grounded the negative probe on the metal chassis and used the positive to check the legs of the ICs. Apparently I'm an idiot for doing this and/or I accidentally caught 2 legs at once and hopefully just shorted a chip only. All was well minus the 1 Oscillator prior to this and now when I power on immediately I hear a loud screeching/white noise followed by what sounds like an Orbital CD played backwards and not in a good way. Keys respond as does the membrane panel and display. No matter what I do there is just noise in the background and all sorts of digital vomit. I'm really hoping I simply just fried one of the chips I tested and that's it. I'm in the process of putting together an order to replace the 6 total chips I touched. I'm really hoping just to get a little peace of mind in the meantime that this is likely all I did and that whatever happened didn't spread down the line to other places.
Oh dear - sounds like you have damaged beyond use of that chip. As montions above replace the chip. As a future tip for measuring things in precarious places tag a little bit of wire onto the leg with solder and measure from the end of the wire. If you have clips on the DMM leads there's no need to touch while powered up.
Old 19th December 2019
  #6
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Quote:
Originally Posted by mrfantastic View Post
Oh dear - sounds like you have damaged beyond use of that chip. As montions above replace the chip. As a future tip for measuring things in precarious places tag a little bit of wire onto the leg with solder and measure from the end of the wire. If you have clips on the DMM leads there's no need to touch while powered up.
I'm never going NEAR that thing again with a multimeter after this. I do plan on replacing every chip I so much as even touched (6 in total and as Jim said they are cheap). I did s brief re-cap of the area I was farting around in last night. Once these chips get here it's in the Synthesizer God's hands. I really hope the damage didn't make it downstream. This is what I'm looking at so yes I'll be praying: U454, U455, U462, U463, U406, U407

https://www.flickr.com/photos/[email protected]/?
Old 19th December 2019
  #7
You should be fine as surrounding resistors and caps might have helped stopping the damage elsewhere.
Old 28th December 2019
  #8
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No dice after swapping all ICs I believed to have been affected. This is what I'm dealing with if it helps.

https://youtu.be/tIj-QzR5964
Old 30th December 2019
  #9
Quote:
Originally Posted by Thisiscobras View Post
No dice after swapping all ICs I believed to have been affected. This is what I'm dealing with if it helps.

https://youtu.be/tIj-QzR5964
Sorry no idea about the synth in particular - I was commenting based on experience of fault finding with IC's. Looks like maybe some kind of corruption somewhere with the sound generation. Probably best to have a proper synth tech to have a look.
Old 30th December 2019
  #10
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JohnRoberts's Avatar
 

+1 CMOS is cheap, and probably not bad...

JR
Old 31st December 2019
  #11
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Farmboy presents's Avatar
I think that you have successfully circuit bent the 600.
Old 1st January 2020
  #12
Gear Head
 
Thisiscobras's Avatar
Quote:
Originally Posted by Farmboy presents View Post
I think that you have successfully circuit bent the 600.
Lmao, thanks I needed that.
Let me know if any of you guys want me to do the mod for you.
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