Tube amp problem

[AceFireForce117]

Hi everyone !

Yesterday, after recording one of my band's guitar players, i decided to play a bit before turning the amp off.
Turn the standby on and suddenly there's this loud low squeal. Did a couple of tests and i've nailed it down to the lead gain. I've noticed when i turn the gain up the squeal's pitch goes higher, while turning it down makes a lower pitch squeal. I've never encountered this kind of problem so i'm guessing the cause is the tube pre for the lead gain ? I'm not sure. Has anyone had this problem before ?

The amp is a engl ritchie blackmore signature 100 head.
Can't continue recording and i need it working now

 

[ProphetofHatred]

The tubes are failing

 

[AceFireForce117]

The power tubes ? god damn it...
Just what i needed right now

 

[bryan_kilco]

Sounds like microphone tube(s) maybe? Like a feedback type noise?

You tracking the live amp?! If so, you may have problems getting the same tone again.

 

[AceFireForce117]

Yeah it sounds pretty much like it..
And yeah i'm gonna have to fiddle with it once it's up and running again to get a matching sound. I'm not that worried, it's for a debut ep but still...

 

[TheWinterSnow]

I want to put money on that it is a preamp tube. Its rare for power tubes to go microphonic like that as they have so little voltage gain to begin with. I have had some weird harmonic screeching coming from the phase inverter tube having oxidation on the socket, moving it around and in and out a few times fixes it, but a good oxidizing spray would do even better.

 

[AceFireForce117]

I want to put money on that it is a preamp tube. Its rare for power tubes to go microphonic like that as they have so little voltage gain to begin with. I have had some weird harmonic screeching coming from the phase inverter tube having oxidation on the socket, moving it around and in and out a few times fixes it, but a good oxidizing spray would do even better.

that's why i thought about a preamp tube. If that's the case, then the question is which one ? and also how the hell can i access the preamp tubes, idk if you've ever owned a engl e650 but you can't take off the front panel and from the rear panel the power tubes block the way !

I'll mess around with it tonight when i have more time, see what happens when i change the pre's

 

[Fredrik-Ablaze]

Microphonic tubes, ive owned 6-7 different engl amps and they have all had problems with microphonic preamp tubes.
The stock tubes are simply not that good

 

[TheEngarn]

Tubes. Don't risk the power transformers. Change them for safety.