Suggestions for troubleshooting a damaged amplifier

Look at the "higher volyage caps" for a start , they tend to dry out and cause mayhem....( hope it helps )

Did it work ok prior to the Pepsi spill? Was it powered up before the Pepsi spill was cleaned out?

I would be concerned with the misc pots not getting cleaned out properly or replaced since they can hide contaminates well.

Drinks like Pepsi are *extremely* corrosive to electronic circuitry - particularly if it happens to be on at the time of the spillage. In such cases - I see probably 3 or 4 a year - my first move is always to examine both sides of the board under a strong light, with a powerful headband magnifier. You are looking for corroded leadouts on small resistors and caps, and the slightest signs of corrosion under and between the pins of the opamps. Often, a resistor leg will be eaten through right where it joins the endcap, and pretty much invisible as a problem to the naked eye. These damaged leadouts can make or not at a whim, which sounds pretty much like the situation that you have. Meat's suggestion of pots hiding contaminants is also very valid, as is his question as to whether it worked before the spillage. Try to get as much info from the original owner as possible. The internal track end connections can be compromised by corrosion, as can contacts inside panel switches for channel selection, channel gain, and effects loop jacks.

You could also try flexing the pcb by pushing on it firmly with the butt end of a screwdriver or similar, to see if you can find an area that is mechanically sensitive. Failing all of this turning up a result, it's signal generator time. If you haven't got a signal generator, use something like a cheapo MP3 memory stick player, with the output taken from the headphones socket via at least a polyester cap of 0.1 to 1uF, or preferably, a little

The key to success with a project like this is patience, and adopting a logical approach. Occasionally, problems like this brought on by spillage, defeat the best of us - from a commercially viable point of view that is - but as you are doing it for self-training and personal satisfaction, then the time it takes you doesn't matter. If you fix this problem though, it's not to say that there are not further, related ones, lurking round the corner. Whenever I get a fix on something like this, I always warn the customer that this may not be the end of it ...

Arfa

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well said, Arfa

id like to suggest checking the input jack(s). clean with Q-tip or in severe cases a 32 cal rifle brush. from the description the problem is localized to the input section. also spray the 3 pushbuttons next to the input jacks with de-oxit or similar.

situations:

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Washing the board as you have is fine but you needed to dry it off quickly, not let it sit for 10 days. That encourages electrolytic action between dissimilar metals which can cause metal to be etched away - or other problems such as moisture ingress into resistors or caps via any small imperfection in the coating. You should have blown as much water out from under components as possible and then dried it by applying hot air from a hair dryer or hot air gun for around 10 -

Water tends to get trapped beneath components mounted flat on the pcb, such as IC's and electrolytic caps. Any water left under these components is BAD...

Without seeing the board it is going to be difficult to offer help. About all you can do is test elctro's for high esr or simply replace them if you can't. Other than that it is going to be a matter of trial and error as far as I can see.