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Please check the impedance switch is wired correctly. or bypass it and go direct to an output jack .
There should be a variable negative bias voltage so check for that.Power tubes dont have to be in for that.
Check your ground on the bias circuit and power tubes.

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

Yes, swap the primary leads to the OT. That sure sounds like positive feedback to me.

I'll have to splice one of them, I left it too short. I've checked the impedance switch, and the bias circuit, haven't identified any wiring issues.

Impedance Switch Wiring,

Orange 16 Ohm tap, also to board (Yellow cutt-off)
Green 8 Ohm tap
Yellow 4 Ohm tap
Output tap to output jack tips

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Could be exacerbated negative feedback as well, so try it.

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

Are you getting negative bias voltage?

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

Swapping the OT primaries did the trick, silent as a liberal in a library on election day! Just running through a crappy test speaker, I'll hook up something more suitable tonight and put the amp through it's paces. Managed the splice quite cleanly -- I can live with that

Now there's a perfect example video of the feedback issue with swapping the OT primaries being the demonstrative fix for others to compare their squeals to. Thanks!

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So, you can also bias the tubes?

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

I didn't have time this morning -- didn't think I'd have time to swap the OT primaries, but squeezed that in. I'll try to bias again tonight. Just so I understand, what is the purpose of the second bias test point? The manual doesn't specify which of the two, though I'm assuming the first.

Update: Okay, since there's only one adjustment I'm getting that the two bias points are one for each tube and bias is set to where both of the points read within the spec range?

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Yes, you got it. Measure between RED-BLACK for each tube. Make sure they are both within range. They wont be identical.

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

Am able to bias, though didn't work on stand-by, had to be fully on, I've got 17mV on one and 21mV on the other without any adjustment. Turning the pot brings the 17mV side down, so I guess it's fine where it is.

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Yes, plates need voltage for the tubes to be biased.

Any joy?

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

Bias seems good, didn't get to test the amp out with a guitar yet, ran out of time again, have to watch my son then off to catch Sebadoh.

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I had little play through this morning, but still on a crappy 3W test speaker -- still sounds good! Though the volume controls are had me questioning things, both the Bright and Normal volume controls seem to affect the signal when I using either of those inputs, is that normal? For example, I plug into the Bright channel and the Normal volume control affects the volume. I'll need to do more testing to determine the exact relation, but I would have expected that those controls only affect the associated channel unless you're using the Linked channel, is that not the case here?

Everything seems to work, I just have to build an extension cab, or the head cab and bring the amp to my studio.

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Each vol control affects only that channel unless in linked mode.
I would first suspect an issue with the wiring of the input jacks.

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

I see what happened. The layout has the jacks in the order of Brilliant, Linked, Normal, where as the chassis has them (if you start from the inner corner) Normal, Brilliant stacked then Linked beside them, so I have everything in the wrong place.

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Should we change the layout? This is a first though.

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

Has the chassis/faceplate changed or have they always been arranged like this? I wired them with the faceplate facing away from me, never thought to check the order as I assumed the layout had them positioned starting with the hardest to access (the inner corner of the chassis) which is the Normal, then the one above it, Brilliant and then the one beside them, Link. However this is not the case.

As it is I'm not sure how the layout diagram (Brilliant, Link, Normal) relates to the physical arrangement which I see as Normal, Brilliant Link. Rather compounding the issue the diagram shows the Brilliant going to the ground lug whereas in the reality the Normal is closer to the chassis ground lug.

Not that you should change anything based on my interpretation Just outlining how I ended up with them all backwards.

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Took the finished Triwatt and half-finished cabinet to the studio the other day, here's a short clip,

http://thicket.to/storage/2017.04.26.Tr ... g_Muff.mp3

Tons of fun! This clip is the Link channel with mostly Normal, Gibson SG, through a modded Boss CS-2 and a Russian Big Muff for most of it, plus an oddball pedal called the reVOLVER at the end. Be warned I'm a pretty loose player

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Temporary name plate...

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