Troubleshooting first build.

[Tapsnap]

This is my first amp build and I am experiencing some problems. Here is the schematic and some pictures.












 Sometimes the amp works at full volume though with a lot of buzz, then suddenly it cuts to half the volume for no apparent reason. I have checked all the voltages and all seem good except for the one at R9. which is 110V not 85V. I have checked all resistors and changed the pots, re-routed the grounds, checked all the connections to the tube holders, pots, jack sockets, but I am still getting the same problem.
One thing I don't fully understand is grounding. A good explanation as to how to ground an amp and where to connect to, but more important, what not to do and why would be really helpful.

[shooter]

Nice floor!!!,
the schematic is good looking, your build looks like my 1st few

look at the board in the is link;
http://el34world.com/Forum/index.php?topic=22495.0
find the achieve section here and check out the how to troubleshoot links

guessing the yellow wires are filament?
If so get them as far away from V1 and associated components n wires as you can.
search grounding in this forum section, the 1st take-away, keep preamp ground from power amp ground

hang in there, you'll be playing soon
the cutout problem probably an iffy solder joint somewhere

[Tapsnap]

"the 1st take-away, keep preamp ground from power amp ground"  OK see, this is what I don't understand. Don't all the grounds eventually go to the same place? I have them all going to the green grounding wire coming from the AC Power. Is there some ground I don't know about that I should be connecting to instead?

[shooter]

here's some explanation n examples;
http://el34world.com/Forum/index.php?topic=9267.msg84015#msg84015

a ground point n a ground plane are somewhat different. a chassis is a ground plane, a bolt n nut are a ground point on that plane.  I'm NOT a theory guy.  everything pre, ground at input jack, everything PA ground at PT bolt.

get the amp reliable, no signal loss plays well, then clean up wiring and grounds, then play!

here's my studio floor, maybe we can collaborate on a Pollock tribute

[sluckey]

here's my studio floor, maybe we can collaborate on a Pollock tribute

If you could figure out how to capture that on canvas lot's of folks would pay good money for it. Especially if you make up some story about how you struggled to reach that point in life. Heck, even prints of that photo would sell.

[shooter]

how you struggled to reach that point in life

that would be a novel stranger than fiction!
My nephew already claimed the floor if I sell the house
It's funny, I have a pretty good group of millennial artist friends, I offer them 1/2 to sell my works, their to lazy to even try!!!

[Tapsnap]

PT is Power transformer; what's PA?

[shooter]

PA = Power amp (section) in your case just the big tube, if it were a PP (push-pull 2 tube) then the PI (phase invertor) should be included as part of the PA section.

[Tapsnap]

So, to clarify, you're saying  that the rectifier, the filter caps and their resistors should all ground to the same place as the grounds of the power tube which is a single lug mounted to the chassis near the power transformer. Then the grounding wires connected to the preamp, the volume and the tone, all ground to the input jack, which is also connected to the chassis but away from the power transformer. Is that right?

[shooter]

Is that right?

yup
here's how I would split up the grounds, red pre, blue power

EDIT, also move your filament wires away from everybody, best you can, tuck along the edge of the chassis

[Tapsnap]

OK, I get it now. Thanks. I can't wait to try it out. I'll let you know how it goes.

[shooter]

I can't wait to try it out.

Take your time, think each section through, solder well, the more "front end" time you devote the more flawless jamming can be done later

[PRR]

> Sometimes the amp works at full volume ...., then suddenly it cuts to half the volume

This is almost certainly a Bad Joint. Find and fix it; then we can talk about the buzz.

[Tapsnap]

Well, I read the "grounding" page on Aiken Amps website and I now I think have a much better understanding of this whole grounding subject. Unfortunately, I had to conclude that I had to redesign the entire circuit board. So here is what I came up with.



Nothing is soldered yet so I can easily make some adjustments. I put in an extra filter cap which I may use if it is still too noisy, but will leave out initially,. The grounding for the preamp centers at "B" and the output and power supply, centers at "A

[Tapsnap]

Actually, that's completely wrong. Ignore my last post.

[shooter]

dually ignored
just take your time, double-check, ohm, you'll be jamming soon

[Willabe]

Here's another good read on grounding, if you haven't read it yet. It's from Merlin's web site, he is a member here and drops in now and then.

http://www.valvewizard.co.uk/Grounding.html