trinityamps.com

At the circled spot on the 2K5 resistor w/ ground: 2.5mV DC

At the circled spot at diode intersect w/ ground: 312V DC

At the upper-oriented circled spot on filter cap w/ ground: 2.5mV DC

At the bottom-oriented circled spot on filter cap (220K resistor) w/ ground: this started at 4.0mV and would slowly drop by 1mV every few seconds over the course of a couple minutes. It went down to 2.8mV after about 4 minutes.



Yep, all are DC measurements except for the AC 690V taken at the PT transformer points, and I'm placing the black probe to ground/chassis. Just put a brand new battery in my meter and am getting the same results.




Yes, I am clipping the black probe/ ground to the metal part of the chassis, with the red probe applied to the various points. The heater AC measurements at preamp tubes 4 to 9 are all reading 0V, and from 5 to 9 it's reading 3V (same at all 4). Output tubes 2 to 7 AC are both 6.2V.





Sweeping the bias pot from fully CW to fully CCW changes the output tube pin 5 to drop from the -1.93V to -1.66V on both sockets.

Yep, I've had all tubes out for all of these measurements/tests and connected to a speaker load.

As stated before, when I did have the tubes and powered it they did all glow/get warm.

Thanks again for all of the help.

Does it matter which lug the red and black wires are soldered to on the jewel light here?

You've got the Zener diode in the wrong place. You've got the Zener where the rectifier for the bias supply should be and the rectifier for the bias supply where the Zener should be. I've cut the mistake from the pictures you posted yesterday. The circled diode is the Zener. You need to swap the two diodes I've indicated.

The heaters run on AC, so doesn't matter which lug you have the black and red wires connected to on the lamp as long as there is one on each lug.

Wow, I can't believe I missed that. Thank you so much. I've swapped those diodes out and am now getting voltage to a couple of the preamp pins:

ALL OF THESE WERE MEASURED WRONG - CORRECT MEASUREMENTS IN A DIFFERENT REPLY BELOW

V1
1: fluctuates from -6.5mV to +6.5mV (same as before)
2: 0V
3: 0V
4: 418V
5:fluctuates from -6.5mV to +6.5mV (same as before)
6: fluctuates from -6.5mV to +6.5mV (same as before)
7: 0
8: 0
9: 419V
Pin 4-9: 0V
Pin 5-9: 890V

V2
1: fluctuates from -6.5mV to +6.5mV (same as before)
2: 0V
3: 0V
4: 419V
5:fluctuates from -6.5mV to +6.5mV (same as before)
6: fluctuates from -6.5mV to +6.5mV (same as before)
7: 0
8: 0
9: 428V
Pin 4-9: 5.3V
Pin 5-9: 924V

V3
1: fluctuates from -6.5mV to +6.5mV (same as before)
2: 0V
3: 0V
4: 400V
5:fluctuates from -6.5mV to +6.5mV (same as before)
6: fluctuates from -6.5mV to +6.5mV (same as before)
7: 0
8: 140V
9: 429V
Pin 4-9: 55V
Pin 5-9: 936V

V4
1: fluctuates from -6.5mV to +6.5mV (same as before)
2: 0V
3: 0V
4: 432V
5:fluctuates from -6.5mV to +6.5mV (same as before)
6: fluctuates from -6.5mV to +6.5mV (same as before)
7: 0
8: 0
9: 433V
Pin 4-9: 0V
Pin 5-9: 946V

Power Tube V5 Pin 2-7: 6.1V
Power Tube V6 Pin 2-7: 6.1V

However I'm still not getting any mV reading at either of the bias points.

Thanks again.

Wow! Something is definitely not right.

It looks like you have plate voltage on the heaters! Did you change anything besides swapping those diodes? Going from memory, I think the heaters were looking okay before and I wouldn't have expected that to change.

Speaking of the heaters, I'm a bit confused at how you are getting different readings on Pins 4 and 5 of the preamp tubes. Those two pins should be connected together so the readings should be exactly the same on those pins. Also, when reading the voltage for the heaters you want to have one probe on the Pin 4/5 pair and one on Pin 9. So you won't be reading those pins in relation to ground. On the output tube sockets you would read with one probe on Pin 2 and one on Pin 7.

Maybe post another picture of the power supply area of the amp. Something that better shows the power transformer wires and the section of the layout I've been highlighting, including the diodes.

Also, what DC voltage do you have on the two lugs of the bias switch that show red wires going to them on the layout diagram? What do you get at the lugs of the power/standby switch where the HT1 and HT1/OT lines connect? Does switching the bias switch change any of that? Read those with the black probe on ground.

one other question that might seem dumb but, you are doing these measurements with the power switch in the play postion, not standby, right?

Also, I can't quite tell from your pics, but I think you have the impedance switch wired wrong. It looks like you have the yellow and red wires connected to the same tab and nothing on the bottom tab. The red wire should go to the bottom tab, not the same tab as yellow.

Ok so I'm an idiot. I was measuring the pin voltages totally wrong...I'm really sorry about that. I have the pins 4/5 reading as they should. Here are what they actually are:

Here are more photos since switching the two diodes: https://imgur.com/a/t21za1i

The soldering on those diodes looks really bad - I had the legs cut pretty short and had to solder a lead to the zener to extend it, and it was a tight squeeze making everything fit again, but I measured everything out with a meter and it shows a full connection. The first couple of photos are with the meter connected to ground and the end and pin 4/5 of V1 to show full continuity for the whole run of those.

It's such a jumbled mess of wires, sorry again for that. Please let me know if anything is unclear from the photos.

V1
1: 412V
2: +/- 6.0V
3: +/- 6.3V
4: -
5: -
6: 409V
7: +/- 5.9V
8: +/- 6.0V
9: +/- 11.5V

V2
1: 417V
2: +/- 4.9V
3: +/- 6.1V
4: -
5: -
6: 410V
7: +/- 5.4V
8: +/- 6.0V
9: +/- 12.1V

V3
1: 426V
3: 139V
4: +/- 6.2V
5: -
6: 395V
7: +/- 6.3V
8: +/- 6.5V
9: +/- 12.5V

V4
1: 433V
2: +/- 5.7V
3: +/- 6.4V
4: -
5: -
6: 434V
7: +/- 6.4V
8: +/- 6.3V
9: +/- 12.4V

Yes, all measurements have been taken with the power switch in full power mode (not standby).

For the impedance switch - I think it was just from a bad angle, and I used a yellow wire (instead of red on the layout) to go from the 7.5K resistor to the 16 ohm tab. I think I have it right, but there are photos uploaded in that Imgur link of it in case.

The heaters are working as intended (I think), I was just going about measuring them all wrong.

For measuring those DC voltages at the bias switch, power/standby switch, etc - just to be certain, do I clip the ground of the meter to the chassis then touch the red meter probe to each of the points? Just making sure before I do it for safety reasons.

Thanks again.

That certainly looks better!

For the impedance switch, I'm referring to the tab for the four ohm tap. That yellow wire from the output transformer should be connected there but that red wire (the one going to the speaker jacks) should be on the bottom tab of the switch (the one that looks like it has nothing soldered to it in your earlier pictures). It will work the way it is, but the impedance switch will be disabled and the four ohm tap will be hardwired to output jacks. I've circled the area in the attached pic. I might not be seeing it right, but it won't hurt to double check.

If all that checks out, set the bias pot so that you get maximum negative voltage at pin 5 of the output tube sockets. It should be somewhere around -35 to -45 volts DC. If that's good, do the Power Up tests starting on page 49 of the assembly documents (Step 10 Power Up, if the page numbers are different than mine). If everything holds, re-measure for your DC Voltage chart. If that looks good, check if you have any hiss/hum at the speaker (the tubes should be in by now). If you can't hear any hiss try Coco's screwdriver click test. If you can hear hiss, try plugging a guitar cable into the input of the amp and turn it up a bit. Tap your finger on the end of the cable. If you get noise that's a good sign. Set the bias before you go further! Once you have the bias set, try playing through the amp with your guitar.

I think you're on the home stretch.

Great! I fixed the impedance switch, another lazy mistake that I somehow managed. Thank you for pointing that out. Luckily I've had it connected to a 4-ohm speaker load for all of these tests.

I'm getting the -39 to -40 volts DC at both output pin 5 sockets with the bias swept. I put the tubes in, but I'm not getting any of the speaker noise/hiss/hum at all through the speaker. I checked the DC voltage charts and everything on V1, V2, and V3 looks great (all reading with 10 volts or so of the manual chart). I checked the fuse and it is in perfect condition.

I will admit that the screwdriver test scares me

However on V4, when touching the probe to pins 1, 2, and 3 it creates a pop of static noise through the speaker upon contact. I'm afraid to hold the probe long enough to get an accurate measurement with the noise it creates, but the reading did look to jump to where it should be. I'm also getting a voltage reading on pin 9 of V4 (which is supposed to be zero), and when probing for measurement it does not send the static pop.

From what I understand of coco's screwdriver test, is this a good thing in that it shows that the socket is sending an output? V1, V2, and V3 preamp tubes did create the pop. Should the screwdriver test be done with the tubes in or out?

There is also no sound at all when tapping the end of a 1/4" cable to any of the inputs.

Thanks again for all the help.

Pin 9 of V4 is a heater pin so you should be getting AC there.

Pop and noise when you probe the pins is normal and a good sign. Not all pins make a pop or noise but on the grids, plates and cathodes it’s good. Don’t let it freak you out, it takes some getting used to but is generally a good sign. Just be careful when probing and keep your left hand behind your back.

I’m out right now, but will check in later.

Don’t be hard on yourself. Everyone makes mistakes on their first build and the Triwatt is pretty advanced.

Got it working!! Well the normal channel at least. I had done a lousy job on the coax wires to the input jacks and the shielding was grounding out. Unfortunately I wrecked the wire to the bright input when trying to fix it, and I don't have enough coax to re-run it, so I'll have to order some and just use the normal channel for now.

Can't express how much I appreciate all of the help I got on here.

Fantastic! I’m so glad it’s working and you found the trouble!