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Little LFO build problem
MUFF WIGGLER Forum Index -> Oakley Sound Systems  
Author Little LFO build problem
Hello everyone.

It would be the smallest module I've built yet, but I can't figure out what's going on here. I've got the Oakley Little-LFO, and at the mo something is wrong. When turned on, the LED lights, but doesn't change colour, in spite of moving the pots. I found that shorting the underside of the pads of the rate pot (with my finger..) brought it to some sort of life. So I checked all the connections around there. This was when I noticed that there are four small holes on the board that have not been used. Closer inspection of the board shows (for example) that R4 terminates in one, and should be connected to the shape pot. There are two more by the rate pot and one by C3.
Have I missed something/been spectacularly stupid? (has been known...(!))


The little holes that appear to go nowhere are vias. These allow the copper tracks on the top side to join with another on the bottom. I normally fill these up with a bit solder but this is not needed for correct operation.

Failure to oscillate could be one of a number of things. The first one to check D1 is the right way around. But it could be something like a small short somewhere.

Do you have a voltmeter or a scope?

Thanks for the reply!
Ah yes. Vias. I knew about those....(!)
D1 is the right way round. I can't see any obvious shorts.
The alpha pots I used don't come with pins sticking down. They have tabs which line up flat on the surface of the board. I'll check these. I'll also give the board a clean with a little isopropyl.

Yes, I've got a multimeter, and a scope without probes (-which are on the shopping list...)


It works. It was the alphapots and their lack of pins. I'd not used enough solder on the middle tab of the shape pot.

Thanks again for the quick response!

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