Electrolyte Leakage?

[TrevorK]

I've got a Yamaha C40 preamp that my father claims is loosing power in either the right or left channel. I Plugged it in and didn't notice a problem with it... so I opened it up to see if I could spot anything weird.

I found that most of the large electrolytic capacitors have a brownish-blackish material that appears to have come out from underneath them. I have attached a picture.

I suspect this is electrolyte that has leaked out of the capacitors. I do not have a lot of experience working with old electronics so I figure I should get conformation from someone who does. It's not a particularly valuable amp (sticker on back says it was made/inspected in '85.... I found one for ~$100 on ebay) but it sounds pretty good and my father likes it.

So my questions are:
Is this electrolytic solution from the caps or something else?
Is it worth it to replace them and clean up the PCB?
What would cause this? Old age? Heat? Some other component failure?

I haven't been able to get it to act up, but I haven't really left it on for any long period of time (maybe it needs to heat up) and I haven't noticed any real sound quality problems as a whole. I appreciate any input. Thanks.

[Netlist]

It's glue to fixate the capacitors to the board. Electrolyte is very thin and would flow over the board. If the amp works fine, leave it as is.

/Hugo

[jcx]

even if there is no visible leakage it is possible that 20+ yr old electrolytic caps may need replacing

measuring ps ripple under load could determine if they still have adequate capacitance left or if they have "dried out"

other Al electrolytics in the signal/feedback path could also be loosing C - smaller cases tend to dry out quicker

you could measure the preamp with RMAA to give you the frequency response to see if you're loosing lows on one channel

[dnsey]

That glue is notorious for becoming conductive with time.
If you suspect problems in this area, it's worth removing the glue carefully and completely, as well as changing the caps.