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[OOF!]

I'm recapping my old lexicon VariSpeech 27 which has been a bit noisy for a while.  I'm wondering what this goop is that is joining 3 caps and going down to the trace on the PC board.  the texture is much like old glue or epoxy, but down at the trace you can see it has discolored a bit.  does this serve an electronic function?
anyone have a schematic of this dinasour?
thanks,
David lawrence

[Mike Cleaver]

Looks like epoxy or some other type of glue used to hold the three capacitors.
Dunno why anyone would do that unless they were loose and pulling at the solder traces.
Perhaps he (she) was trying to stabilize the caps without going to the bother of re-soldering them or repairing the lifting traces.
It has no electronic function.

[ssltech]

It's not uncommon for manufacturers to do this to help with vibration. Remember that some gear goes into OB trucks, and gets bounced, shaken, rattled and bumped for several years. The solder joints fatigue on many electrolytics because of the slight-but-persistent resonant-load flexing they can exert.

If I'm building anything for a truck install, I ALWAYS use a silicone "caulk" (or similar) to help share mechanical loading on large electrolytics.

Keith

[OOF!]

thanks for the replies- that makes perfect sense.
david

[ssltech]

The solder connections at the base of the transformer to the back of the picture look like they might use a little investigation...

While most look good, those look dull and a little brown; either flux-related corrosion, or it might just be exposed copper on the wires, but it's hard to tell. If it's flux corrosion, I'd remove the old solder COMPLETELY with sole solder wick, then clean up with alcohol before resoldering.

Just in case...

Keith

[Andy Peters]

Mike Cleaver wrote on Tue, 04 September 2007 12:22

Looks like epoxy or some other type of glue used to hold the three capacitors. Dunno why anyone would do that unless they were loose and pulling at the solder traces. Perhaps he (she) was trying to stabilize the caps without going to the bother of re-soldering them or repairing the lifting traces. It has no electronic function.

The various safety agencies (CE, TUV, etc) require that "large" components be held in place by something other than component leads.  If there's no mechanical structural support (bolts, bracket) then a dab of RTV or silicon spooge does the trick.

Now, if the spooge was coming from the BOTTOM of the cap, and the cap package was bulging, then the cap had leaked electrolyte and must be replaced!

-a