Metropoulos Forum

I added a 100pF bright cap to the high treble channel a few days ago and noticed that I now get a high pitched feedback squeal when the volume passes 8 and sometimes even on 4-5 if I'm running two OD pedals stacked into input 1 of the high treble channel.
could the feedback stem from the bright cap?

I should note that my JTM45 is still not mounted in a head case so there is no aluminum foil at the bottom. still, there was no problem before the bright cap was added.

I also checked the preamp tubes' grid wires, everything sits above the chassis as per the instructions, the presence pot's wire also runs along the edge of the board and away from the other pots and their wires so it's probably not the presence pot's lead dress.

Elad E wrote:I
I should note that my JTM45 is still not mounted in a head case so there is no aluminum foil at the bottom. still, there was no problem before the bright cap was added.

neikeel wrote:

Elad E wrote:I
I should note that my JTM45 is still not mounted in a head case so there is no aluminum foil at the bottom. still, there was no problem before the bright cap was added.

should I take that as a nod toward taking the bright cap off or toward getting a headbox?

Elad E wrote:head case

Elad E wrote: two OD pedals stacked

stef wrote:

Elad E wrote:head case

Elad E wrote: two OD pedals stacked

Exactly

thanks,

may just fix some aluminum foil to the wood plank the chassis sits on at the moment until I decide if I'm going to build my own or go for a pre made head box.

it seems V1 tube ,a 4 year old Tung Sol, went bad (the edges of the metal deposit at the top turned black).
replacing it with a new one solved the problem (and opened up the frequency response altogether).

however, I'm still having power cut problems:http://forum.metroamp.com/viewtopic.php ... 24#p424724