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HI all,
Having issues with my ef 86 channel on ,my dc-30. Basically high pitched whistling on when I crank the gain (volume) knob past 2 o’clock and then when I wind the master past 9 o’clock.
The 12ax7 channel works perfectly fine.

To me I don’t think it’s the tube (Phillips miniwatt) as I tried another of them (don’t have any others to try) and same effect.

Checked my lead dress from the input socket (shielded cable)- was o.k.
Wiggled my lead dress from rotary tone switch to the 220k resistor to ef86 and noticed the whistling would kind of go away and come back when moving it. So I replaced with shielded cable (grounded at pot end) and no luck, still whistling.

Amp friend of mine suggested putting a small pf cap b/w gain stages on the ef 86.
Where would be the best place to do that?

Any suggestions at all?

With guitar plugged in or not?

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

plugged and unplugged.

di you try to reverse the OT leads. Might be worth a shot.

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Hey Stephen,
Correction - it only whistles when guitar is plugged in or when the cable is left plugged in. When there is no lead plugged in, it doesn't whistle.
Cheers
daz

Is the grid stopper resistor right on the pin of the EF86? Can you post a close-up of the input thru EF86; that part of the amp??

Hmm, I see they are. Shielded wire used?

Try another guitar - cable . It could be the pick up / cable.

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

I noticed some people ground pins 2 & 7 (shield) of the ef86. Might try that as well.
I used shielded cable only the inputs. I'll take some pics tonite.
Thanks Stephen.

whistling is gone - reversed the OT leads it seemed to do the trick. Strange!!

Not really, the OT has to be in phase with the amp. So reversing them is pretty common fix for an amp squeal.

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps