DMD-2 Pin 21 producing voltage

falco_femoralis

falco_femoralis

Well-known member
Hi all, I just made a DMD-2. The rate pot would not allow for adjustment of the modulation rate so I tracked it down to pin 21 of the FV-1 producing 0.68v. I lifted that pin from the circuit board to isolate it from any stray tracings and the voltage remains at the pin.

My plan is to remove the chip and put a new one in. Anything else I should check out first?
 
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Just for S&G, could you try popping a different EEPROM in there (or force it to run one of the internal programs) and make that measurement again?

I don't think anything in code (corrupt or otherwise) should be able to cause what you're seeing, but it's worth a shot before ripping the IC off the board.
 
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Robert said:
Just for S&G, could you try popping a different EEPROM in there (or force it to run one of the internal programs) and make that measurement again?

I don't think anything in code (corrupt or otherwise) should be able to cause what you're seeing, but it's worth a shot before ripping the IC off the board.
Click to expand...
I have a Spatialist I could try, but last night I tried removing the EEPROM and taking a measurement - the result was the same
 
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Robert said:
Make sure you can remove the IC cleanly. If so I'll send you another FV-1 IC.

If not, I'll send a PCB as well.
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Thanks, I'll keep you posted. My plan is to see how it goes and perhaps swap it with the chip from my Spatialist, which isn't built yet. The solder from the one pin came up pretty easily so that's good. I'm trying to plan a technique for securing the chip back down. I've done SMD transistors but not a chip like this yet.
 
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Clean all of the old solder off the pads, tin one corner pad, position the IC then heat the corner pad to secure it in place.

Now use some liquid flux and solder the pins on the opposite side to the anchoring corner, then the remaining side.
 
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Robert said:
Clean all of the old solder off the pads, tin one corner pad, position the IC then heat the corner pad to secure it in place.

Now use some liquid flux and solder the pins on the opposite side to the anchoring corner, then the remaining side.
Click to expand...
Well, that didn't work. In hindsight, I could have been a bit gentler. I'm going to forego the DMD-2 and put something else in the enclosure.
 
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