Random Squealing Noise

[♫♪♫]

Ok, in the past couple days, my Marshall DSL50 head seems to make a weird squealing noise...

I have no idea what is causing it, but yeah its freaking me out so I haven't turned it on for fear of wrecking it.

Help!!!!

[TweeDLX]

Try pulling the preamp (small) tubes one by one and see if it it stops. You can also lightly tap each one to see if it starts. Could be a microphonic tube. You may be able to use the microphonic tube in another position, so try swapping it around..

Mike

[♫♪♫]

I switched tubes 1 and 4...


I noticed however, that the bad tube glows pretty dimly...compared to the rest. So, I guess I should just replace the thing correct?

And if so, would I be better off replacing them all, or just the offending one. I used to use a lot of overdriving to push my amp, so I am thinking that is why the tube has gone pretty quickly.


Finally, I noticed that the first tube had a metal cover over it, and I was wondering if this is actually good for the tube....it would seem it would trap the heat inside, but I dont know...?

[rockon1]

Personally with new production pre amp tubes I'd replace just the offending one. Reliabilty isnt thier strong point so if they are working I'd leave em alone. In other words they have made past the possible initial crap out or infant motality point. It is important to have some spares on hand though too. You could replace them all and keep the good ones as spares too. If one suffers "infant mortality" your covered. I stock many spares so either way its not an issuefor me.
Cover? Interestingly enough Ive read they can actually draw heat away. Either way I dont think its a issue. Its mostly there for RF noise and retention. Some claim they can hear a difference with them off(the amp sounds better). Bob