Bright Channel Buzz

[coco]

I just finished my second 5E3 but I have built a lot of other amps.

This one has a really annoying buzz/distortion at about 200 Hz maybe, on the bright channel, #1 input only when the Vol pot is maxed. the sound is so bad until the amplitude decreases thens its normal. Sort of really bad overloaded sound with a very hard / harsh edge. All other inputs seems fine and sound the same as my first build.

I have:
cleaned V1 socket;
reheated all the connections around input jacks, V1 & tone control;
reheated component connections on eyelet board;
replaced the 68K resistor for #1;
cleaned the input jack;
replaced the .1 uF coupling cap for that side of V1;
replaced the Vol pot; and
checked continuity to from tube to board and input jack.

No luck. So I thought I'd throw this one up there for help.

Any ideaas? This is very obscure (it will probably end up being something simple).

[TD_Madden]

Using any shielded wire inthe preamp?

[coco]

Using any shielded wire inthe preamp?

Thanksforthe reply,

No, for the 1" or so to the input resistors, do you think it's necessary? Input to board? AND board to V1?

[TD_Madden]

I was thinking from pin 2 of V2 (12AX7) to the "normal" volume pot, with the shield grounded there.

[coco]

I added a shield to the rear of the chassis and that was an improvement. The 2 metal can oil in paper .1 uf caps used for v1 were replaced with 'orange drop as they seemed to be attracting noise. That was an improvement. A bit of lead dress on v1 helped again. It's all good so shielding that long run is next on the list. Thanks for the tip.

I'll report back with some pictures and progress later.

[Thorny]

Clean up the lead dress a bit

Clean up your lead dress by making your wires to the tube sockets as direct and short as possible. I think that might take care of your problem. Do the chopstick test to see if moving wires helps your problem. It could be a bad solder joint someplace, but it sounds like you have tried there.

Also, rule out a noisy tube problem.

[coco]

Here is a picture of the final assembly. I'd say it's much improved.

Changing the two .1 coupling caps to orange drops from metal cased oil in paper; shielding the rear chassis opening; using shielded wire for the long lead from vol pot to V1 and some very minor lead changes got rid of the badly distorted buzz when playing some low frequency notes..