[analog97]

Hello all.  I have selected 3 pictures of caps that look questionable.   The brown junk at the bases might be electrolyte, but I don't know for sure.  I wondered if a manufacturer might have used some product in addition to soldering them to the pcb.  I would appreciate if someone with experience could take a peek and provide comment.   The pics aren't perfect, but they do give you the idea.  Thanks in advance for any comments.  Very much appreciated and no, these are NOT from a JH product.

[Bill Epstein]

Looks like sealant that dripped to me. Only way to be sure is to remove one leg of the cap and measure the capacitance.

[analog97]

Thanks, Bill.  So, some kind of brown sealant is used to install some caps?  This brown stuff is only located on the caps. I did not know that.  Thanks for the reply.

[Bill Epstein]

I think the sealant I referred to is seen at the power connections, quick-connects: brownish amber blobs.

Old school construction, especially of speaker crossovers, was to pour varnish or shellac over all the parts to dampen vibrations. It looks like the same method was used here to keep the quick-connects in place and some dripped.

Here's a good example, the crossover of the mighty XLHs:

[WGH]

I had a lot of caps go bad on a motherboard, I took some pics:

http://www.wghwoodworking.com/ka7.html

Wayne

[analog97]

I am still trying to figure out if manufacturers comonly used a brown sealant to "glue" electrolytic caps to a PCB.  That would help me.  Thanks.

[palasr]

Yup - the brown stuff is commonly used to glue the base of caps to a board.  You see this a lot in CRT devices where very high B+ is present, perhaps as an added layer of insulation should something arc.  Sometimes you'll also see a silicone caulk-like goo they smear on that hardens slowly over time. 

When a cap dies it is usually from overvoltage or a dried out dielectric due to environmental stress (like putting a cap next to a heat sunk component), or simply age.  Common visual symptoms are either a bulge on top of the cap along the "vent" ridges, or they'll leak along the rubber gasket and leads at the base of the cap.  This leaked material is generally white to gray in color, and can be tougher to spot.  If in doubt, remove the cap, and check it out of circuit.

-Richard

[analog97]

Thanks, Richard.