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As I was troubleshooting what was causing the VRM to not work properly I reflowed some of the solder points around the VRM. Then I went to test the lugs on the VRM control with my meter when I accidentally touched something that caused a small spark. I later went and tried to power up to see if the reflowing helped anything and now I'm getting no sound at all. I did notice that one of the diodes overheated when I was in there with the soldering gun so that may be what is to blame. Are the diodes part of the VRM circuit only or are they part of the non VRM signal chain? I jumpered the VRM to see if it works without it but now it no longer does.

The two black diodes are the rectifiers. If they are gone, you would not get any voltage to the amp or to the VRM. If you shorted out the supply, it could have taken them with it.. You'll need to test back down the power suplly chain so Is the fuse OK. ; Is there AC at the diodes: is ther DC after them etc..

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Stephen
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When I test them for AC or DC do I test them with the negative lead at a ground? I just wanted to ask so I don't burn something else out.

The fuse didn't blow but I know one of the diodes looks like it was affected by the soldering iron heat so it's very likely that is part of the problem.

First disconnect the amp right after the rectifier diodes and before the first filter cap. If either of the diodes isn't working it could harm the caps. Then carefully measure from ground to each of the PT's two main secondary wires (ie not the centre tap) for AC voltage. with AC it doesn't matter which lead is to ground. For DC it's easier if you put the black lead to ground/chassis. If you can lift the ends of the diodes (with the amp powered off) you should be able to use your meter's ohms or diode test setting to check if the rectifier diodes are OK. They should conduct in one direction but not the other.


Soldering guns are usually too hot for soldering semiconductor devices, like diodes and FETs. I would instead recommend a smallish 40W soldering iron.

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Great tones come in small glass jars!

Actually I meant soldering iron rather than gun. There's a connection where the two diodes meet that is really difficult to get into to reflow the solder and that's where I thought I damaged them. I think at this point I probably need a bit more experience to be able to get beyond this point so I was wondering if I can pay Stephen or Chris to fix it? Stephen or Chris let me know.

http://www.youtube.com/watch?v=kqYDRxdgnC0

Chris is going to take a look at my amp. Hopefully I didn't blow up the Mosfet.

Fixed! Thanks to Chris!