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Greetings--I had time to get back to this:

OK, I have taken some basic readings of the signal path with a scope.
I started at the grid 68k resistors in the preamp stage.

I could follow the signal (a triangle wave from a little signal generator) all the way to the grids, the inputs, of the EL84s.
Then, at the plate points of the EL84s, as they lead to the OPT,
I got nothin'.

I also did a simple test of the OPT: the B+ leads to plate is:
Blue: 300 ohm ; Brown 260 ohm
reading plate to plate lead, I get the sum of those.
Thus it seems OK?

I seem to have isolated problem in the power stage--other possibilities?
I still have no sound. I performed these tests, naturally, with a speaker hooked up.

The OPT-to-speaker line reads as an open circuit--nothing--
(despite the blue/ brown readings above)
this is a sure sign of a dead OPT, right?

The resistance will be very low, less than 1 ohm, so measure it accurately as possible.
Do you have power cathode tube bias voltage?

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

Couple of things come to mind. Are you able to rig up a cable to hook your guitar straight into the phase inverter? As in connect it to the input of one of the coupling caps to bypass the whole preamp.

Also have you tried a different tube in the phase inverter?

How about checking all of the wires that come off the board to ground to see if the signal is shorting to ground somewhere.

An easy alternative to a signal generator that I have used for car audio is an iphone app that generates tones. You will need to rig up a cable, but it is much cheaper than buying a signal generator for occasional use.I was thinking about making a cable to go from my iphone to a pair of these, and another for my guitar to a pair of them as well. That way I can inject a signal where I want, and it is less likely to short something out.
http://www.litchfieldstation.com/xcart/ ... 276&page=1

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My Current gear..
Ibanez RGA121
Gibson Les Paul Studio
EVH 5150 III
Peters dual channel
EVH 2x12 cab

Check your impedance switch wiring

Trying to find a picture of another build

eco's and mine looks the same



yours

pretty sure the output wire is hooked to the pin closest to the impedance wires

Switch set for three clicks.

output on a
yellow goes to one
green goes to two
orange goes to three

HG: Do you have power cathode tube bias voltage?
Me: If that is pin three of the power tubes, I get about 12 volts
at each, consistently. That's based on readings taken during two separate tests,
noted in the build-ledger.

On the OPT leads-to-speaker input . . . if I scrub the
meter probe a bit on the lead as it comes to the impedance switch, I do get something like
1 ohm or less, intermittently. Is it "ok" if that is an intermittent reading?

I take some heart that nobody here has said outright, "you cooked the OPT at some point, you oaf"
but I swear I never ran this rig without a speaker; I am still suspicious that the OPT is hurt or MIA.

Thanks for notes LP-man. I'll digest that and post back, but I note I followed a signal from the pre-amp all the way to the
grids of the EL84s. It was at the plates that I seemed to loose the signal.
----
On sazafraz's note: I hear you, I agree, my impedance main lead out is wired to the tap labeled "C"
(on my switch the other tap is labeled "A")

The image you have and in the Manual shows the tap on the switch closest to the
1,2,3 leads ("A" on my switch) receiving the main OPT out. Can anyone attest to the importance of tap selection A or C
on the impedance switch? The switch is set for three clicks.

HG? (I thought he had already "checked off" on my photo of my impedance switch wiring, but
my suspicions have gone there too.)

A and C have no continuity between them so important

As for the wires which numbers did you use to hook up to the switch the ones on the top ( switch side) of bottom (pin side) the do not line up to each other you need to hook up wires to the numbers on the pin side

So you can fix up the switch and see where that lands you

Yeh, sazafraz, you get free beer,
you spotted the problem--(though I was about to try the same fix,
serendipitously--I swear)
the impedance switch tap was mis-wired. (!)

I think the instructions could include a variant of sazafraz's advice: make sure the
tap chosen is the one closest to the impedance-wires, not necessarily the "center"
(or at least not necessarily the one marked "C") tap.
I am mildly astounded that I didn't cook the OPT; it must have registered some sort of load.

I haven't played this much, but I hooked a Telecaster to it, and both channels, all controls,
boost, work fine, quiet: it chimes, it crunches!

In short: it's alive!

A cool cabinet for this is standing by and I'll post pictures this weekend once it gets installed.

Glad you got it working. And OT survived . Think about you imp switch being upside down it might effect which tap your switching 2

Now all I need for Christmas is a VRM and Low watt TT for my tweed

Here's the amp in its case; it is a 2 x 10 rig.
The color and grill cloth scheme are accidentally
(I only realized this after the fact) the same as
the Marshall Mercury series from c. 1972.
I just went for something that said "c. 1972!"

Ok, a new issue. I've been playing the amp for two days and it has sounded great.
Both channels have worked fine.
However, tonight, the TMB channel stopped working.
Its symptom is that it hums loudly--
the volume knob controls the loudness of the hum.
(The hum is the note Bb, --trivia).

The amp is back out of the cab and on the workbench.
This hum seems independent of the cliff-jack inputs.

Suggestions? A connection obviously went wrong, but what are some likely culprits?

The normal channel still works fine.

First try swapping out V2 and see if it goes away. Tubes go bad. Check all the voltages on v2 and see of they are normal. If they are and the tube is known good, then I would start by inspecting all the solder joints in the TMB channel and re soldering any suspects, or just redo all of them.
Note that It could also be the TMB half of V1.

I like your cabinet BTW and a 210 is glorious!,

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

Oh, another update, we are using new 10A impedance switches now and there is no question about correct terminals.

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

Like the Cab mini blues breaker head chassis in a combo cab

This hum issue was a bad V2 tube! These were new (fine Russki, Svetlana) tubes--this one was just a dud
(short lived, .i.e). Thanks for suggesting this. I don't know when I have had a pre-amp
tube be the source of a problem ( I recall once, in a hifi amp I have), but it does happen.

The amp sounds great, by the way. Stephen, do you have a sound clip section?
I am a drummer by main trade, but I can run it through its paces and post some clips.

(Attached pic of Marshall Mercury--similar color scheme as my cabinet).

Yes, clips go in the Clippage section. it's all good!

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

Simply GORGEOUS in it's cab! Did you build the cab? Fine work!
Gene

Great looking cabinet, kind of reminds me of a Morris esque cabinet.

I've always wanted a cab with that grill cloth, it's got a cool look to it.

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