Capacitor leak?

[imnewbie]

I just bought this tube amp and opened it up. Shockingly I found some residue around capacitor where it contacts the pcb. What is it? Is it harmful to the amp? Should I return the amp?

[Enzo]

Larger parts, like that big filter cap, have a higher center of gravity, and can shake more when the board vibrates. WHen parts like that shake, they stress their solder connections, which eventually crack. Buy gluing larger parts down in addition to soldering them, it keeps them more firmly in place and more steady. This reduces shaking and helps keep solder from cracking.

SOme board makers put a film of glue underneath parts, while some glob silicone rubber or hot melt glue around them. Some glue jobs are neat and even, some just ooze out from around the part.

That is what it looks like you have there, to me.

[cogsncogs]

If you take a probe and:

1. Hard and stiff or rubbery; it's glue.

2. Sugary, yellow-brown in color; it's solder rosin.

3. wet (but not always), reddish brown and looks like this: Bad Caps; it's probably electrolyte.

Wayne

[benb]

Put a finger on top of the cap an see if you can wiggle the cap, make it move in any plane

The glues used in these things can indeed make it complicated to determine whether a cap is leaking stuff. I replaced some tall caps in a PC SMPS a while back, they were a couple of inches tall and glued to the component side of the board with glue that it took an x-acto knife to cut loose, AND they had the obvious sign of bad caps, bulging tops. In my case the stuff at the bottom was obviously glue. In the photograph it's less obvious, but I go with the consensus and say that looks like glue and the cap is (at least visually) fine. Are there other caps around that size on the board? Not that it would be conclusive (as all large caps could be leaking), but I'd expect them to have the same stuff underneath.

I've seen in older equipment large axial caps held down with plastic wire ties, You can't mistake a wire tie for a leaky cap. Thesedays PCB space is "too valuable" to have large components laying down. I'm surprised it's not more common for through-hole resistors and diodes to be standing up on modern boards. I first saw that many decades ago in a small transistor radio. Oops, I'm rambling and derailing, sorry.

[imnewbie]

This and 3 other similar caps cannot be moved when wiggled, may be b/c it's glued like you guys are suggesting.

The other three caps and other larger PCB parts don't have anything like that residue as seen in picture.

I probed the residue and and it started coming off like pieces of crystal; solid and "light yellow with hint of greenish brown" in color.

[cogsncogs]

Looking at your photo I'd say it's solder flux from the wave soldering process. I've seen this many many times before.

I probed the residue and and it started coming off like pieces of crystal; solid and "light yellow with hint of greenish brown" in color.

Yup, that's solder flux alright. I see flux all over that board. If the cap isn't bulging, getting very warm/hot or your amp isn't humming or sounds "funny", your probably 99% OK. If I had the amp here in front of me, I could probably give you the other 0.99%!