VCO - 10 ohm resistors on voltage rails burning.

WooDaWii · Joined: Jul 12, 2014 Posts: 14 Location: Quebec city

Today I got one of my two VCOs to oscillate but the second one burnt a pair of 10 ohm resistors (the ones situated near the power caps/connector), I found some shorts and corrected them, replaced the resistors and they burnt again. I pretty much went through the entire board looking for broken traces/shorts already, so I don't really know what to look for now. I know for sure the pot wiring is fine and have verified it many times through the wiring process. Any advice pointing towards possible solutions would be much appreciated!

elmegil · Posted: Tue Jan 13, 2015 11:07 pm Post subject:

You quite likely fried a chip or two when you had the shorts, and still have shorts or nearly so. Measure the resistance between the rails (after the 10R resistors) & ground, if it's ridiculously low, that's your thing.... If you've socketed your chips, pull them out and measure again, if it's still ridiculous then there's another short you haven't found. If it's not, put them back in one a time until you find the bad one(s).

If you haven't socketed, try to figure out which ones get hot first and pull them the hard way and see if that resolves anything.

WooDaWii · Joined: Jul 12, 2014 Posts: 14 Location: Quebec city

took a quick look at it yesterday to find a very small solder bridge between two joints on the main voltage lines. That would make sense. Still haven't fired it up yet, hopefully ICs are ok. Seems to confirm that so far in this project almost every problem is a broken trace or a solder short. Thanks!