The Amp Garage

Great! looking forward to seeing photos and maybe a sound clip.

Good to hear you figured it out. Note in the Bluesmaster layout the switches shown are slide types, but the lug connections are shown as they would be for toggle switches.

So I have a question. Using this board and this transformer The AC bias tap should be 60VAC, transformer puts out 45vac. Is this enough voltage or do I need to do something different to get 60 volts? Just have to reduce the 3k9 resistor to something smaller, maybe 470 ohms or so. Correction, 47 to ...

Dragon1 wrote: ↑Thu May 16, 2024 9:19 pm So I have a question. Using this board and this transformer The AC bias tap should be 60VAC, transformer puts out 45vac. Is this enough voltage or do I need to do something different to get 60 volts?

Just have to reduce the 3k9 resistor to something smaller, maybe 470 ohms or so.

Raoul Duke wrote: ↑Thu May 16, 2024 8:02 pm Not hearing any weird noise from the PI or OT, so I guess V3b plate wire is ok where it is for now?

Do you mean the OT primary connections/NFB?

It's the same as placing two same-value resistors in series to reduce voltage instead of one at the same total resistance. In the case of two resistors, half of the voltage is dropped in each one, current is the same, so half the power (V*I) is dissipated in each.

Thinking about this more and running some numbers here is what I've come up with. Voltage dividers are linear (though a pot may have a different taper) meaning if you think of the divider as attenuating a certain percentage of signal voltage, it does not matter if that input is 10V or 50V, the rati...

Kagliostro wrote: ↑Thu May 16, 2024 9:01 am but I'm not able to figure why at 1/3 of the voltage as output the dissipation will not ne high

At very low voltage the current draw is reduced. Power is I^2R, and the reduction in I^2 becomes dominant.

I see it has the pro tour option, 12 chassis mounting bolts ;^)

Yea, sorry for the diversion. If you went ahead and wired the rest of it up you'd have been fine. Hopefully the learning was worth the trip!

Raoul Duke wrote: ↑Wed May 15, 2024 2:00 pmMakes sense - the second ground reference wasn’t in the circuit - so it compensated by pushing all the voltage to one (grounded) side. Do I understand that correctly?

That's it. I seem to recall the same question coming up in your 102 build.

Do you have heater leads connected between the two sockets? If not that would explain it. I thought I saw a back/white twisted pair.

That says that the 150R from 2 isn't connected to ground.

Yes. If you disconnect the PT heater leads you should measure ~150R to ground from pins 7 and 2. There are two diodes and a resistor across those pins, but that shouldn't affect the measurement significantly. P.S. If you measure pin 2 or 7 to ground with the heater leads connected, you should see ~7...

I’ll go over everything one more time, but I’m fairly certain that I don’t. Is it safe to measure heater voltage with the leads off the socket and just hanging in the air? No problem. Measure across the leads since you have removed the ground reference. The only other thing I wonder about is the te...