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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Vibration failure of components in bass combos
Yet another one, an unsupported 3W resistor , with a fractured wire.
Doesn't matter what maker, none of them seem to take this failure mode into consideration. The common factors bass combo (so far only bass ones ), large Rs suspended off the board, can be mounted vertically or horizontally, the fracture always at the pcb and looking at the cross-section of the wire and a copper colour then presumably work-hardening via vibration of wires with a high copper content. I'd never seen Rs supported on ceramic bead insulators with this failure so used them on replacements. Then i thought a rigid pillar could exaserbate the problem by a fulcrum effect plus chance of them vibrating / rattling in use. So later I used beads or PTFE vias for tin-plate (discarding the pins ) for most of the stand-off and finishing with a blob of RTV silicone. This one I'll try blocks of that orange silicone rubber cut from the pressure roller at the output of a junked photocopier. Small hole "drilled" through each so making fuzzy contact with the R wire and theoretically damp any tendency to vibrate. Incidently anyone know what the incredibly firm adhesion system they use for bonding that rubber to the steel shaft running through the rubber. Has anyone seen the pro solution to this problem by any maker or any other ideas? With a number of such large Rs in a line then I tie each to adjascent with stout silicone sleeving with slight tension in the sleeving and anchor to the pcb at the ends. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net |
#2
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Vibration failure of components in bass combos
N Cook wrote:
Has anyone seen the pro solution to this problem by any maker or any other ideas? Makers like Peavey use hot melt glue or something that looks like very thick PVA woodglue. Ron(UK) |
#3
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Vibration failure of components in bass combos
Ron(UK) wrote in message
... N Cook wrote: Has anyone seen the pro solution to this problem by any maker or any other ideas? Makers like Peavey use hot melt glue or something that looks like very thick PVA woodglue. Ron(UK) Glooped over the body of the R and the leads or just the leads, cross-linked to something else or just glooped onto the pcb ? -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#4
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Vibration failure of components in bass combos
N Cook wrote:
Makers like Peavey use hot melt glue or something that looks like very thick PVA woodglue. Ron(UK) Glooped over the body of the R and the leads or just the leads, cross-linked to something else or just glooped onto the pcb ? All the examples I`ve seen have had the stuff poured over the component body to an adjacent component or to the pcb, never on the leadouts. They seem to use something akin to Evostick around the bases of verticle smoothing caps. The hard white stuff - more like pva glue than hot melt - tends to discolour and crack off the component in time, probly due to heat. I doubt using standoffs improves the reliability much unless maybe it's the old fender method of using a brass tube fixed through the pcb with the leadout wire soldered at the lower end but free to move in the tube. Crossover networks often have big components secured using cable ties around the part and through the board. Big components fall off circuit boards, it`s a law of nature (and bread and butter work for repair technicians ;^) Ron(UK) |
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