New Express build

[BgTonalPursuit]

Just cranked on a new Express build, and I'm having a couple issues.

The biggest problem is that with the gain anywhere from 0-9.5, there is a proportionately loud (and TERRIBLY TERRIBLY so, at that) 120 Hz buzz. I've built a few amps, but I've never had one act like this. The layout is fairly close the Ceriatone layout, with the caps in the bottom right corner instead (farthest from input). Any suggestions?


There is also a fair amount of 60 hz noise that I can't attribute to anything (DC heaters, referenced to ground, with about 1VAC on them). This noise proportionate to the master volume (added in) which is much more normal behavior from what I've encountered.

Any input would be greatly appreciated!

[doctord02]

Gut pictures would be a big help here in identifying potential problems...

[BgTonalPursuit]

Forgot to mention that after 9.5 (ie, maxed) on the gain, the 120 Hz buzz goes away...like completely.

Here's gut shots. Forgive the extras, they're for reverb and PA B+ voltage control. The 3rd stage is an anode mixer.

[BgTonalPursuit]

Forgot to mention that after 9.5 (ie, maxed) on the gain, the 120 Hz buzz goes away...like completely.

Here's gut shots. Forgive the extras, they're for reverb and PA B+ voltage control. The 3rd stage is an anode mixer.

[IMG768]http://i288.photobucket.com/albums/ll18 ... G_0337.jpg[/img]

[IMG768]http://i288.photobucket.com/albums/ll18 ... G_0336.jpg[/img]

[IMG768]http://i288.photobucket.com/albums/ll18 ... G_0338.jpg[/img]

[IMG768]http://i288.photobucket.com/albums/ll18 ... G_0339.jpg[/img]

[IMG768]http://i288.photobucket.com/albums/ll18 ... G_0340.jpg[/img]

[IMG768]http://i288.photobucket.com/albums/ll18 ... G_0341.jpg[/img]

[Noel Grassy]

BgTonalPursuit, Howdy and welcome to the forum.

Forgive me for asking, but what's the function of the horizontal "solder log" in the bottom picture?
Have you reviewed any of the files with pictures of Francesca?
In any high gain amp, let alone one that's designed to hover on the fringes of instability, lead dress is paramount.
May I suggest building something much simpler? A kit might be more in order until you get tools and skills together to perform things like fabbing a chassis.
This is not meant to discourage you entirely, but more to save you from welding your heart to some other inconveniently located life support organ.
Start by tearing everything out of that chassis and studying what folks on
this forum have built before you. There's no logical place to start isolating
your hum problem otherwise.

[Lonely Raven]

Wow, that doesn't look like any ceriatone build that I'm aware of...

[BgTonalPursuit]

Noel,

The horizontal thing is the star ground for the preamp. It's connected by one wire to the star ground, on the blue board to the right, for the PA and first filter caps.

I've build several high gain amps, and tho I sometimes do things unconventionally I do have the golden rules of lead dress in mind. This has been the first build to give me a bit of trouble.

I've been able to solve the terrible hum by moving the tone stack/gain pot ground to the first stage local ground, rather than the 2nd. I was under the impression that connection to the ground at the stage with a DC path to ground was preferred. My issue now is that I cannot deduce why this solves the problem.

Forgive me if I sound as though I took offense, I certainly do appreciate the help. Though at the moment, I'm just a student, I do take pride in my work and sometimes it gets the best of me.

[Noel Grassy]