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Hey guys, first time builder having an issue.
(I completed the build, but had these issues. I’ve since taken it apart to check all the component values & redo it. Just thought I’d throw this out to see if I missed something.)

I’m not getting 340v @ r10 & c6. First off, I get 400v on the left side of the resistor coming from the OT & power tube. On the right side of the resistor, my voltage starts around 270v then drops continuously to 24v. I only get 6.5v @ pins 1 & 6 on the preamp tube. I get 1.7v @ pin 3, but 0 @ pin 8.

I've attached a pic of the turret board with voltages to clarify what I’m taking about.

Voltages with 6v6 & vrm @ 400v:

@ fuse - 123.9vac
heater wires to ground (pin 2 & 7 power tube, pin 5 & 9 preamp) - all are 4.1v ac
diodes - 377v & 380v
vrm power cap:
@ idle - 87v
@ 5 - 158v
@ max - 467v

While checking the voltages I tapped the pins on the power & preamp tubes & heard pops from the speaker, but with the odd preamp voltages I never plugged a guitar in.

So….. after reading through many other posts my thoughts were a misplaced jumper or bad solder joint.

I checked & rechecked the wiring. Everything matched the printout. The jumpers on the back were correct, but I replaced them just to be sure. I removed & resoldered all of the tone stack capacitors & resistors. Reflowed both grounding locations & tested for continuity. Added heat shrink to the coaxial cable (one was grounding out on the board). Checked my wiring to the volume & tone pots. Put it all back together…… and got the same results.

I guess my question is, could something on the power side be causing this? The wiring to the power tube and transformers is correct. In my uneducated thinking, if the voltages are correct there, the problems on the preamp side.

I’m hoping it’s a bad capacitor. I had to order a capacitor tester, so I’ll find out when it arrives. The resistors tested correct.

Any advice or troubleshooting help is greatly appreciated.

Thanks,
Stephen

Looks like way to much of a voltage drop across the 47k resistor between the two 33uf filter caps. The colour codes on the resistor looks right. Check to see where the jumpers under the board are correct from that point.

And do you have any pictures of the full build with board installed

check that the grounds are in the correct places as well.

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

Well, I’m at a loss…

Since my last post, I’ve completely re-populated the board, minus the diodes & mosfet.
Tightened the grounds, rewired the jumpers, tube sockets, & pots.
Fired it up & have the same issue.
(I’m not getting 340v @ r10 & c6. On the right side of the resistor, my voltage starts around 270v then drops continuously to 24v. I only get 6.5v @ pins 1 & 6 on the preamp tube.)

Since I heard pops through the speaker during testing, I plugged in a guitar.

Other than the low volume, this thing sounds great! (Volume & Master volume need to be @ 6+ for clear sound)

No hum. Treble & bass pots work. Fat switch works. ’Tude switch works.
Man, the overdrive sounds awesome when you put the vrm @ 9-10!

So…
Since my pots are working, can I remove the jumpers from the board to them, to troubleshoot the preamp section?

I’ve got to get a chopstick or wood dowel to poke around.

I'll post my full list of voltages later.

Here's some pics & a video demo.
https://youtu.be/AuY2rChRee4

I don't see the little jumper that is supposed to run between the grounded ends of R7 and R8 on the board (the two 2K7 resistors right beside each other). Maybe you put it on the bottom side of the board, but if it's missing C6 and C7 won't have grounds and none of the preamp power supply will work right.

Also, do a continuity check with your ohm meter to make sure that everything that is supposed to be grounded actually is.

Good luck!

Thanks for the reply mitch. The jumpers there, it's just under the board
I'm building a cabinet now, just letting the amp sit for a while.
I've ordered some wire & will attack again in a month, with a fresh set of eyes.

Are pins 4&5 of v1 tied together?
Heater voltage should be 6.3VAC at least, with that mains voltage, 4.1 is too low.

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

So I took some time off, & built a cabinet. I got some “scrap wood” from my aunt (100 year old heart pine to woodworkers) & threw this together.

Next, I decided to start from almost scratch. I pulled the board & removed all the wiring to the tube sockets & pots, leaving the transformers, led, & heater wires. I resoldered them to get a baseline on my voltages.

Wall voltage @ 121 VAC

Heater wires:
Pin to ground: 3.48 VAC
Pin to pin: 6.98 VAC

It's high, but I've seen other posts where diodes were added to drop the voltage from the transformer. I might have to go that route later.

That cabinet looks really good. Great to give that 100-year-old pine a new life in a neat project.

Heater voltages will read high if there aren't any tubes in place.

Success!!

Well, almost

Everything sounds great, voltages are good, but I've got that squeal problem with the vrm & master volume maxed, & the volume above 8. I've read this is a lead dress issue & I've included pics, to maybe get some feedback on what to move or change.

The voltage problem from the first post ended up being a volt meter problem. It reads weird on the preamp side, but 2 other meters read fine. It was probably wired correctly then,but my soldering skills have improved greatly from that first attempt to the last, and I'm more confident in these joints not giving me issues later.

Thanks for compliments about the cabinet mitch, I'm totally stoked with it! Oh, & thanks for the plans Stephen, they made it very easy!

Glad the amp is almost fixed. Try moving wires around with a chopstick or a similar wooden stick while the amp is squealing to see if you can reduce the squeal. Do you get the squeal in both settings of the Tweed/'Tude switch?

It's just in the 'tude mode. Sounds fine with everything maxed in the tweed mode.
I'll try some chop sticks & see what happens.