Weird Heater Supply Problem - And other solutions!

[Littlewyan]

Use a chopstick if you have one. A valuable tool

It can be something in the house causing it. I get a lot of interference in my rehearsal space sometimes. I also had a lot of issues when I built this amp into a small Pignose chassis and could never get it to be quiet or not oscillate. There might be hope for your's though as you have a decent size chassis.

Does the buzz get worse when you plug into the low input? Are all of your grounds connected correctly? Checked them with a meter?

[marshallnoise]

I did some reading and determined I better get the guts of this amp into a different chassis. So I built a chassis today. Pics will follow at some point.

The current issue is that the OT is on the opposite side of the chassis as the PT. So I understand that long runs from the OT are not good and if they pass by the preamp, then noise will absolutely happen. I spent some time with grinders, cut off wheels and my welder and came up with a new chassis that is a bit smaller than a full size Marshall chassis. It measures in at 24" x 7" x 3". It will have plenty of room for mods down the road if I want and I am leaving it rusted up a bit with a nice patina. This amp is as much an art piece as anything else.



EDIT: The grounds check out good and the hi-input just amplifies the same noise as the low-input.

[Littlewyan]

That's pretty cool that you made your own chassis!

There are a lot of amps out there with the OT on the preamp side but I don't know how they're wired. Like I don't know if they run the wires on top of the chassis or straight in at the preamp end.

[neikeel]

OT and PT at either end is no issue. Look at oranges and hiwatt. Just keep your secondaries to the output jacks shortish and ideally have the output tubes fairly close too.

[marshallnoise]

Yeah, the long runs are the problem. I had to use the tube socket holes that were already in the chassis. So the OT secondary AND primary leads had to run a long way. Bugera uses ribbon cable for all their connections and several daughter boards and stuff.

[marshallnoise]

Is it bad practice to have the filter caps located directly underneath the power transformer?

[neikeel]

Is it bad practice to have the filter caps located directly underneath the power transformer?

By that I presume your caps are going to be properly mounted to radial cap mounts horizontally to the side walls of your chassis (said he hopefully) and not glue gunned. In that case no problem. Other way is axial caps on a cap board, which again can sit inside under your PT.

[marshallnoise]

Is it bad practice to have the filter caps located directly underneath the power transformer?

By that I presume your caps are going to be properly mounted to radial cap mounts horizontally to the side walls of your chassis (said he hopefully) and not glue gunned. In that case no problem. Other way is axial caps on a cap board, which again can sit inside under your PT.

Haha message received.

[Littlewyan]

Take your time doing it. I went through exactly the same process as you. Built it into a chassis that wasn't suitable, couldn't make it quiet, moved it to a proper chassis .

[marshallnoise]

Take your time doing it. I went through exactly the same process as you. Built it into a chassis that wasn't suitable, couldn't make it quiet, moved it to a proper chassis .

Yes, I am taking my time now. I can't believe you tried to stuff this amp in a Pignose!

Here are some pics. I have started to drill holes and killed a step bit already. Switched to a holesaw and its working better.

IMG_20170929_124119013_HDR by Paul Abbott, on Flickr

IMG_20170929_124959386 by Paul Abbott, on Flickr

IMG_20170929_131625408 by Paul Abbott, on Flickr

IMG_20170929_140607948 by Paul Abbott, on Flickr

IMG_20170930_135952601 by Paul Abbott, on Flickr

Dimensions are 24"x7"x 3". Total coincidence the other chassis was virtually the same.

[Littlewyan]

Haha. The Pignose G40V is a very similar circuit, so I just modified it. However it sounded terrible, was noisy and with the treble above 5 it would oscillate!

For the holes you should use a hole punch. Much easier. Not that cheap but if you use them a lot then the cost isn't so bad .

So you're building a rat rod amp

[marshallnoise]

Haha. The Pignose G40V is a very similar circuit, so I just modified it. However it sounded terrible, was noisy and with the treble above 5 it would oscillate!

For the holes you should use a hole punch. Much easier. Not that cheap but if you use them a lot then the cost isn't so bad .

So you're building a rat rod amp

Ratrod! Exactly! That's a great description.

Using a hole punch would have made much more sense but my step bits worked fine for all but the big holes.

Holes by Paul Abbott, on Flickr

Holes by Paul Abbott, on Flickr

Not the cleanest. But "Rat Rodding" makes the mistakes just part of the theme. LOL

[neikeel]

[marshallnoise]

Ordered a few goodies for this thing. I decided to hit up ValveStorm for some hookup wire instead of using the cheap RadShack crap I was using before. I also ordered some new 9 pin sockets because the ones I have won't fit or mount up. I made the holes too big on all of them, but at least the power tube sockets fit just fine. I used #8 1/2" Teck screws to self tap them into the chassis. Worked like a charm.

I also got 12 bronzed chicken head knobs that will go with the rat-rod motif. https://www.amazon.com/gp/product/B01F6 ... UTF8&psc=1

This whole process pretty much reeks of "do it right the first time, dummy." Or "an ounce of prevention is better than a pound of cure."

But its fun!

[Littlewyan]

Got to learn somehow mate. Can't learn unless you cock up . I speak from plenty of experience

Those control knobs look pretty damn cool! Do the sockets feel secure with the self tap screws?