Did I damage the OT or the valves?

SunDevil

Normal routine-  a random set of circumstances (I'll spare you the details) led to me powering up a valve amp with no speaker attached and only checking if the issue meaning extreme low volume was the lack of a speaker after swapping out a pedal and plugging direct into the amp!

It was switched on and off between these and whilst it was on with no load for probably a minute in total, only around 10 sec of that cumulatively would have had any signal into the front end

The amp plays fine, but when you turn it on or off, you get a static-y 'sighing' sound - it's louder when you switch on than off - I'm assuming (or is that hoping!?) that I've damaged the 6V6s or the rectifier valve, rather than the OT

Any steer from you fine folks

There's an Ampete or similar in my future now!

Danny1969

Did you have a speaker cable plugged into the amp but no speaker on the other end of the cable ? some amps have the output jack shorted to protect against no load but a speaker cable in the socket would defeat that 

SunDevil

Nothing plugged in @Danny1969 - not sure if an earth reference is more likely to save the OT at the cost of the power tubes?
No fuses blew
The noise it’s making when I power up/down is new after the above

SunDevil

A bit more info, as the noise sounds very valve like

The amp runs x4 6V6s and was in half power mode when the above happened - I flipped the position of the 6V6s (outside pair became inside pair) and that made no difference

I swapped the Rectifier valve - no change

pulling the PI valve left the amp totally silent (probably obvious) and swapping other 12AX7s from other positions in the amp made no difference, but putting a trusted old Ei 12AX7 in that the position before it (not clear if that’s the driver or reverb mixer?) does reduce the level of the ‘waves on beach’ noise I described in the original post

I have a new quad of 6V6s coming and one of the current JJs does look a bit dodge (while powder on the spacer) but given I’ve moved it around, I can’t see how it can always be producing power in every half power mode scenario? 

Danny1969

There's a lot of things that could in theory go wrong as the voltage on the valves  / primary side of the OT will build up and that could damage the valves but also the coupling caps possibly from stage to stage. In some amps the caps are not far from their max working voltage on a stable operating condition. 

ICBM / ecc83 will know more than me in this regard. Although I've fixed a lot of valve amps I don't have the model knowledge they do 

ICBM

What amp is it?

You would need to have had it turned up quite loud for there to be any likelihood of damage, unless it’s one of the extremely rare amps which will self-oscillate at full power with no load connected.

The strange noise is coming from the preamp if removing the PI stops it, so unlikely to be related to running the power stage with no load.

Almost all valve amps are far less fragile than popular myth says, it’s only really a risk if the amp is producing a lot of power.

SunDevil

Thanks Gents

the amp is a Divided by 13 FTR (Deluxe / Super a like) and the volume was at about 2pm (in half power mode)

i spoke to Two Rock last night and they were of a similar view (very unlikely to have damaged anything) so my working assumption is that I’m now just hyper-aware of something that was already there and the next stage is be more forensic in the preamp valves 

nick79

I had a Mesa Studio 22 that made that sighing sound when turned off, I’ve no idea why it but worked fine all the time I had it so I never worried about it too much! 

Not much help to you I know but thought I would just mention it