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Ok, so I have finally finished wiring this kit, and I'm ready to take some voltage measurements. I have a couple questions first before I begin:

First, I have some spare parts leftover: two 2k7 carbon comp resistors, a 1M carbon comp, and the switch used for the optional boost circuit. Are these resistors all used for the boost circuit that I did not install? I cannot find them anywhere on the main layout or schematic.

Second - and I'm probably just being paranoid here - on page 41 of the manual, there is a bold print reminder to never operate the amp without a load... but then immediately following are some instructions for powering the amp on WITHOUT a load, then installing the rectifier (again, without a load)... and then plugging in a speaker before testing with the preamp and power tubes in. It makes sense to me that it would be ok to turn the amp on without a speaker load as long as the preamp and power tubes are also not yet installed, but I want to make sure I'm reading this correctly before I blow something up.

Any advice?

The 2K7s are used for the boost. You should have at least one on the board from V2A pin 3 to ground the second one gets wired to the switch for the boost. The 1Ms are used on each of the HI input jacks. If you have those all in place and still have extras then they are indeed extra parts.
You are reading correctly. You can run without a load ONLY if you do NOT have the power tubes installed. When I first built my amp, I plugged the speaker in even when I had no tubes just to be safe.

_________________
Les

http://www.soundclick.com/unimind

I do indeed have the two 1M resistors on the hi Z inputs installed, and there is still the one extra carbon comp. Good to know I'm not missing it elsewhere.

Ok, thanks for the tips, I'm off to test!

Ok, I have tested B+ and the plate voltages with only the EZ81 installed, and here are the results:

AC mains: 120 VAC
B+ (no tubes): 434 VDC

V1 pin 1: 429 VDC
V1 pin 6: 429 VDC

V2 pin 1: 430 VDC
V2 pin 6: 433 VDC

V3 pin 1: 430 VDC
V3 pin 6: 428 VDC

V4 pin 7: 434 VDC

V5 pin 7: 434 VDC

These measurements do not at all match the chart on page 43 of the manual. Is thos because there are no tubes installed? I know the manual says the voltages should be slightly higher, but this is not slight Do the plates really get basically the full on B+ voltage, or have I messed something up?

Can't test with tubes just yet, since I do not have a cab at the moment.

Voltage tests without tubes installed are almost meaningless. You will get some crazy high voltage readings.

_________________
Great tones come in small glass jars!

Ya..don't be afraid to install the power tubes when you do the voltage checks....as long as you're not cranking away on a guitar plugged to the amp with the volume turned up you won't hurt anything if the speakers aren't connected.

Would a dummy load suffice for testing the amp WITH tubes but WITHOUT a cab?

If you're more comfortable with a dummy load sure..go with that. Remember a transformer works with audio. Has to do with magnetic fields changing at audio rates. With no audio the transformer is just a dc resistance for the output tubes. There is no impedance transfer etc.

Ok, then, thank you. Something about all that boldface print in the manual has made me a little wary of turning the thing on.

So far you are doing it correctly. As for the voltage measurements, they wont be close untill all the tubes are installed.
The startup procedure is indeed, intended to slow you down and make you think.

Check B+ first - make sure it's reasonable, then install tubes & connect speaker or dummy load) and measure voltages. Connect speaker and listen for sound.

The "TMB" model does not have a boost switch. Is yours a Plexi model?

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

Ok, so I've finally hooked up an 8 ohm load and tested some voltages with all tubes installed. I know, it's been a couple months (as a public school teacher, the beginning of the school year absolutely destroys any free time I would normally have).

Most of the measurements are close, but some are off by enough that I would worry if I knew exactly why I would have reason to worry (remember, rookie here!). I'd appreciate it if some of you more experienced fellows would have a look at these measurements:

AC Mains: 120
B+ (All tubes installed): 362.3

V1
pin 1
expected: 155vdc
measured: 144.8vdc
pin 2
expected: 1.0vdc
measured: .983vdc
pin 6
expected: 155vdc
measured: 144.2 vdc
pin 8
expected: 1.0 vdc
measured: .945vdc

V2
pin1
expected: 180 vdc
measured: 143.1 vdc
pin3
expected: 1.5 vdc
measured: .915 vdc
pin6
expected: 272 vdc
measured: 265.1 vdc
pin8
expected: 180 vdc
measured: 143.3 vdc

V3
pin1
expected: 220 vdc
measured: 212.7 vdc
pin2
expected: 52 vdc
measured: 52.7 vdc
pin3
expected: 75 vdc
measured: 75.5 vdc
pin6
expected: 217 vdc
measured: 206.3.vdc
pin7
expected: 62 vdc
measured: 50.8 vdc
pin8
expected: 75 vdc
measured: 75.7 vdc

V4
pin3
expected: 12 vdc
measured: 11.61 vdc
pin7
expected: 345 vdc
measured: 350.6 vdc
pin9
expected: 340 vdc
measured: 337.8 vdc

V5
pin3
expected: 12vdc
measured: 11.57 vdc
pin7
expected: 345 vdc
measured: 349.6 vdc
pin9
expected: 340 vdc
measured: 339.0 vdc

V6
pin 1
expected: 292 vac
measured: 308.3.vac
pin3
expected: 350 vdc
measured: 361 vdc
pin7
expected: 292 vac
measured: 308.3 vac


Thanks in advance for any help/advice you'd be able to offer from seeing these measurements!

I think they are fine. Remember that different tubes measure different voltages, they aren't precise devices. They vary across manufacturers as well.
Play it and see what you think. Let your ears be the judge.

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

Finally got the opportunity to play the amp briefly on a borrowed stage monitor. It's not the ideal set up, I know, but I think it works! All of the controls are working, and both channels behave as expected... I will have to take a closer listen for tone once I finish saving for my own cabinet.

Thanks for the help, everyone!