Need some electronics help!

[TCMSLP]

Could you borrow an ESR meter from somewhere?  This would test the capacitors in-circuit and reveal if they're defective.  It could save you some work, unnecessarily swapping components.

I do remember seeing similar white stuff on a board before, but this had been stored in a damp environment and also had dead bugs involved.  I think the white fuzz was general corrosion mixed with tightly spun spiders web or some other form of insect coccoon/nesting thing.

I suspect in this situation you're correct though ...

[TCMSLP]

It was me who mentioned checking the capacitors in circuit.  An ESR meter will a) check the actual useful capacity of a capacitor and b) check the (effective?) series resistance.  Essentially, it'll tell you if a capacitor is good or bad.  

http://en.wikipedia.org/wiki/ESR_meter

It's a very useful tool to have but does cost about £70 here in the UK.  I'd suggest borrowing one - I'd loan you one myself but it's the one bit of test gear I haven't yet bought.

I'm assuming the 'regulator' is actually some sort of switched power supply, generating +/- rails from whatever the input voltage is.  In this case I'd expect the capacitors to be quite fundamental, plus quite likely an inductor or two.

However, I imagine failed capacitors will simply prevent the regulator from getting up to voltage.  The only exception to this would be if they were internally shorted.  You can test for this by placing the multimeter on 'resistance' (or conductivity test) mode and placing the probes over each capacitor.

You'd expect (assuming the kit has been powered off for some time) each capacitor to initially show a very low resistance (practically a short, 'continuity test mode' would probably initially emit a beep), this will slowly (or quickly depending on cap size) increase as the capacitor charges from the current supplied by the meter.  Eventually you should read a very high resistance.   If the resistance continues to stay low or the continuity test continues to emit a beep then something isn't right.

However, this test will be effected by other components in circuit so can only provide a rough indication.  An ESR meter would be the best bet.

Whilst on continuity or resistance mode, you can test diodes.  They should read high resistance (no conductivity) one way, low resistance (conductivity) the other.  Again, results can vary greatly due to the surrounding circuit so results can be vague or change (as surrounding capacitors charge/discharge etc).

I'm only an amateur - someone who has more experience with repairs may be able to offer more useful advice


Steve / TCM

[TCMSLP]

Did you try replacing the capacitors?  The data sheet for the MAX680 shows the 4 (?) capacitors are directly related to the generation of the appropriate voltages.

The data sheet here (http://datasheets.maximintegrated.com/en/ds/MAX680-MAX681.pdf) indicates which capacitors are related to which charge pumps (the + or -).

I'd perhaps be tempted to lift the legs of the outputs (or cut tracks) and ensure the basic voltage pump is working correctly;  There could be something else downstream causing problems.   However, if you haven't replaced the capacitors, looking at the datasheets, this would be the next step.  

I wouldn't give up just yet