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Started this build two years ago, but due to travel and life the amp has just been finished up recently. Initially the checks on the amp where good, however once I fired it up and started playing it... obviously there's a problem.

When switched to standby, everything is good (tubes glow, no fuses pop). Switch to ON, w/ or w/o a guitar plugged in the amp hums quite a bit. With a guitar hooked up the notes are very distorted almost sounds like an oscillation. (This is all on channels no overdrive.

Below are my tube readings, I see there is a problem with the PI section. However I checked everything and it looks/measures fine. I'll post pics and a clip later. Thanks.

No suggestions or help?

I would think the PI would be OK, the voltages follow the correct pattern and are closeenough allowing for different tubes.
With hum, you have to go back and check the grouding and cable dress and look at the coax closely to make sure there is no shorts or stray pieces of wire.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

I'm assuming the 340VDC at Pin 9 of V4 is a typo on the sheet... Well I looked closer at my inputs, and I was missing the jumper on the LINK jack (attached). Which quieted down the amp, but it still hums some. The real problem is the very distorting/ringing when playing any notes on the guitar. Also a question about those coax signal wires, when it was convenient for me I used a twisted pair. I would still ground the shield per the schematic. Example in picture attached, is a 2 conductor cable used to connect the signal (+) from the BRILL and NORM jack to V1. Is carry more than 1 signal within the cable fine?

I would think the twisted coax would be fine and your work looks good. Can only say that the desgin, layout works so you might want to check the latest docs since it's been a while.

Where did you get the parts and board from?

And the note "340VDC at Pin 9 of V4 " comes from where??

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

I've used the documents posted on the forum to build the amp. I purchased the transformers from you guys and the rest I sourced myself.

340VDC comes from a document also on the forum (6V6 Voltages). Also here is a sound clip of the amp, it still hums moderately and notes are very distorted.

http://youtu.be/mbMvjBKSIF0

Can you give us some pictures of your board and wiring? Hum can be caused by lots of things...We need to be able to see what you're working with.

Also, people will help you on here, you just have to give it time.

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--Bryan

Here it is

I see some pretty long signal wires travelling along the board. Those either need to be made to run right against the metal of the chassis or be shielded. There's a lot of gain available in this amp, and there's absolutely no room for any compromises with the layout. I didn't quite understand what you're saying about using twisted wire, but running two different signals within a single shielded wire will give you crosstalk between them.

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Great tones come in small glass jars!

All the previous shielded cables were replaced to be single conductor/signal cables. In addition, I replaced most of the wiring on the input/tone control end. With only the three remaining signals untouched, left as seen (three RED arrows). I'm still getting humming and distorted played notes.



On the other side of the board, what do you recommend I tackle first, i.e. to switch to shielded conductors? Thanks.

Move the wires around V3,4 and see if that helps. Esp. on the grids. This is quite sensitive.
Have you seen the large size picture of a Triwatt Build?

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

What large size picture?

This one - http://www.trinityamps.com/ForumGallery ... _board.jpg

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Thanks.

I tried moving around the grid wires on V3/V4, unsuccessfully. Pin 2 on V3 is short, Pin 7 on V3 is shielded wire. Pin 2 on V4 is short, Pin 7 on V4 is shielded wire. I noticed something interesting when playing music through the inputs. When the amp is ON, lots of hissing and distorted music. As soon as I switch the amp OFF and leaving the music playing through the input, the output (music) clears up beautifully. It's much quieter, but it sound "normal" when I switch the amp from ON to OFF.

Here is a sound clip:
http://youtu.be/0Q2MZXAFV1E

Turns out C22 and C23 were connected in reverse and not grounded... so only connected to R46, R45, D6, R28 and R29. I'm surprised it even worked before.

So something is still not right, it doesn't seem there is much gain... i.e. when connected to a 12" speaker and the volumes maxed out, it's still fairly quiet.

So I rechecked my voltages, V4 is way off. Sort of fixed an issue with the bias only going up to 11 mA. I unplugged the 910K resistor from the switch. HT2 is 418 VDC and HT3 is 406 VDC. I wonder if C22 and C23 were damaged? They look fine.

Looks like the caps (incredibly) survived. But the PI is way off. Check cathode path to ground, and voltage ahead of the plate resisitors. There's something way wrong there.

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Thanks Stephen, I figured out part of the problem. The shielded cable I was using on V4 for the plates/grids (pins 1, 6 & 7), was grounding out. I temporarily cut the shielding and the voltages came back more in line...



So I'll fix those and report back.

Looking better. that should do it. Shielded wire to plates should not be required. I would advise you use basic solid core for that.

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

FIXED! Awesome... sounds amazing. Thanks for all the help, it has been a longgg road