Old Traynor YBA Mk 2, transient silence

[GerryJ]

Hello, maybe someone can identify this - I have an early 70s YBA-1A Mk 2 Traynor bassmaster (2 EL34s & cooling fan), was serviced in the 90s, usually works fine. I fired it up after 8 months storage and a move. and initially there was virtually no sound- none whatsoever, as if the speaker wasn't connected. Did a few resets (has a red reset button in the back), no change. Powered it off, then back on once, no change, but second time, now works completely normal.
It did this a few yrs ago but I thought in retrospect it was early power tube failure, as one did short out a few months later. Currently has new tubes with little use.
?..What gives? Maybe needs time (if not used often) to charge up the filter caps? It still has those 2 large metal caps that hang down like tubes, but all the parts look good both inside and out. Thanks for any ideas!

[xtian]

Maybe the switch itself is an issue? Does it have a standby switch? Those are prone to pitting from arcing, making them failure prone.

[martin manning]

I fired it up after 8 months storage and a move. and initially there was virtually no sound- none whatsoever, as if the speaker wasn't connected.

When you switched it on and got no sound, was anything working? Pilot lamp, fan, tube heaters? If not, perhaps the circuit breaker is failing.

Maybe needs time (if not used often) to charge up the filter caps? It still has those 2 large metal caps that hang down like tubes, but all the parts look good both inside and out.

If an amp is not used for some time the filters may draw a lot of current initially, get hot, and in the worst case, explode. They may"reform" and recover most of their function over some time, minutes or hours, but if they are not shorted you will usually get sound right away, possibly with a lot of 120 Hz hum.

[GerryJ]

Yes, when switched on, pilot lights, fan & tubes all came on. Come to think of it, while the power tubes did glow, it was probably just the heaters, as the plates were dark. Upon repowering, I Did hear the beginnings of a loud AC hum & quickly shut it down. The 3rd time, it powered up normally. Maybe it was the filter caps re-forming...
Re- standby switch- appears to work, but I should clean it (& the others) to make sure.
Thanks!
These old Traynor Mk 2s with their Massive transformers & high voltages are a little intimidating when they misbehave! But it's got the 3 prong grounded mod & I follow procedure (drain the caps, etc)- never got a shock from them after the original 2 prong cords were replaced.

[LOUDthud]

It's important to always use the Standby in these amps. If you don't allow the tubes to warm up, that 560V goes down stream to the 450V cap for the preamp. It will eventually fail. On later versions of the amp, there is a bleeder resistor that limits Voltage to that preamp filter cap.