Vibration testing of combo amps

Waste of time. Vibration failure in those amps can be from overtones and resonates along with main frequencies that can hone in on weak spots.

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Sounds a likely reason.

When fixing replacement resistors to ones that have fractured, always at or in the board, these days I add a ceramic bead insulator near the resistor body and then slightly compressed block of that orange silicone rubber found on photocopier pressure rollers that abutt the fuser roller, between bead and board to , in theory, damp any vibration. Given a free choice of the material for such resistor leads, what would you choose.? Obviously the copper rich leads must work harden and then fail. What about brass pins or multistrand copper wire swathed in solder to bulk up to rigid, any other suggestions ? I imagine if you placed a small solderable collar on the component side of the pcb then the lead would fail at the top of the collar instead. Where heat is the problem , so failed joint , rather than failed lead, I run the lead through the pcb and along the trace for a more distributed solder joint.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

The softer the lead the less it's likely to fracture correct? Personally I am a vintage amp tech. I really won't work on point to point wiring unless it's one of mine or a friend's in desperation. I have 4 high power tube and one SS combo guitar amps. 3 Peaveys (2 Artist 1 Special) a newer digital Waller DSP 100, and a 70's Fender Twin Reverb that was a basket case that I traded a cheapo acoustic guitar for. Also have two 50 watt heads, a Laney and Fender Bassman. I've had problems with the SS Peavey and intermittent connections that seem to come and go. The amp I used the most back when I was gigging was the Twin. Smaller gigs with limited stage space I used the Waller because it had some built in effects. I repaired the Waller under warranty myself after it developed a digital noise when idle. Talked to Waller tech support and it was a known problem. Gave them my credentials, they said go ahead and do the modification.

As far as stress related failures in combo amps goes, Peavey seems to lead the way as far as what I've worked on. I can only imagine some of these newer amps like Berringer and the likes made in China crap. Good luck to you, you must be a younger man as i haven't the patience to do anything but the oldies made in the USA and the UK. (love my AOR Laney Pro Tube 50 head)

We never used to get many stress related failures in those old point to point hand wired valve amps despite - or maybe because of - long component lead lengths. Even the old AC30`s despite looking as tho they had been assembled by an enthusiastic schoolboy, were pretty reliable in that respect. Of course in those days, we used the old technique of making a sound mechanical joint first, then soldering it! The problems started when PCB`s were introduced.

I cant really understand why anyone would want to vibration test a customers amplifier, unulss it`s looking for dry joints, when a rubber mallet or chopstick will suffice. Surely any piece of kit has a 'vibration lifetime' (MTBF thro V?) and I cant think why anyone should want to shorten it by deliberately shaking it. Every minute spent on a vibration table is one minute closer to failure in the field (IMO)

Ron(UK)