Glued down capacitors

[ToneArm]

Grrr.. I just wanted to have a moan about 1980s japanese amplifiers where they glued all the capacitors to the circuit board! The extra leverage needed to get them off invariably tears the traces no matter how much care I take. Does anyone know a cunning way round this annoying problem?

The capacitors are fanned out closely around a pair of transistors that get so hot they are blackened and the pcb around them badly scorched. Why no heatsinks or shielding?? Amazingly they still work but i will replace them anyway for reliability.

Glyn

[Diabolical Artificer]

Sometimes you can twist them off, depends on there size or I soften the glue with a blowtorch, being careful of coarse. Or cut the caps off using a big pair of cutters, then gently get the glue and bits of cap body off using a blow torch. Watch out for the fumes.

Andy.

[Goldie99]

If it's an 80's Japanese board, I would have thought you should be able to completely (& carefully) desolder the cap terminals first, using a solder sucker & desoldering braid, to the point that there's no solder connection left - that'll minimise any stress on the solder pads / traces while you deal with the glue / removing the cap.

If they won't desolder without damage to the pads / traces, then I suspect the problem may be more related to thermal damage of the pcb, for which there's not much you can do - once it's happened.

Poke a soldering iron in the top of the cap, this soon melts the glue without heating much else up.

[Craig Sawyers]

Gluing capacitors to single-sided boards, and in pro-audio amps is common for different reasons.

Back in the day I used to be TD of Wharfedale. We acquired Cambridge Audio in about 1990, and their various products used axial electrolytics and single sided boards. We had a significant number of failures on arrival because as a result of mechanical shock during shipping, and the weight of the capacitors tore the tracks off the board. We changed to using hot melt glue to mechanically secure the cap to the board and that cured the problem.

In pro-audio amps, there is the same shipping problem, but also a vibration issue during use, either in a club/disco or for sound reinforcement at a rock concert. Again, hot melt is sometimes used (but can soften because of heat) or a much more aggressive adhesive like the Japanese amp the OP has. Strategic holes in the board and use of tie grips can be used for high weight axial components (no help with radial caps though - hot-melt/glue is the only way to go).

Craig

[ToneArm]

Thanks for the ideas folks, i'm working on the amplifier again this evening so will feed back what works!
Cheers
Glyn

[Goldieoldie]

You could try Ronsonal lighter fluid. It seems to soften most glues.

Cheers Pete

[ToneArm]

All done and dusted, PCB tracks repaired and the amplifier is working nicely now. Thanks for all the tips - suffice to say, there is no easy way round this one, other than care and perseverance!

Glyn