Ibanez Tube Multiefects problem, help!

[bioroids]

Hi, I need your advice or any help with this:

this is an Ibanez PUE5 Tube multiefects, from the 80's, it has a Tubescreamer, a tube distortion using a 12AX7 and other effects.

The valvular distortion makes a funny noise, like a high frequency resonance or oscillation, more prominent during the decay of the notes.
It was once fixed by changing the valve, but it didnt last long, and now the valve was again replaced but it didnt improved.

I never messed with tube pedals, so ANY advice you can give me is welcomed.

Thanks ahead

Luck

Miguel

[petemoore]

Since it's easy...a small cap at the input signal to ground might help, and will cut highs. I use test wire with alligator clips, clip one side to ground, clip a cap on the other side, and touch it to the input, just inside the DC blocking cap...or use a second testclip wire to make a more permanent temporary way to test the mod., so I can twiddle tone knob etc. and see what I think..
 Depending on the need for high end content [does it have a tone control?], it may be of some use to you.
 Technically it probably shouldn't need one there, but maybe it's worth a try for a kwik dirty solution? [If it works].

[bioroids]

Thanks for your help, I tried this but didn't work out. I mean, it did solved somewhat the squel, but also it loosed too much highs

I think the valve is defective, if anyone knows how to test for that, please post it.

The squeal is very strange, it sounds like crickets or other bugs, is not the classic high freq oscillation problem.

Thanks again and good luck

Miguel