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Prior to installing tubes got these voltages:

Line-121 VAC

Voltage at first filter cap: 89 VDC-VRM @ idle and 448 VDC-VRM @ max

Secondary Voltage: 652 VAC

Heater Voltage: 7.0 to 7.1 VAC

Build guide (pg. 48) "Leave VRM at idle and measure DC voltage on the first 50uf capacitor. It should be over 400 VDC." I am only getting over 400VDC (448VDC) with VRM at max setting. Do I need to investigate?

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"The only problem with being retired is you never get a day off"

It will drop when tubes are installed.

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

I wouldn't mind seeing some clarification on this as well. I'm not there yet but without tubes your voltages should be higher and they should drop when you install the tubes. If the VRM is controlling the AC voltage level going in, shouldn't the voltage readings be low when its at its minimum level and highest at the highest level? My understanding is that the VRM is acting like a Variac. Inquiring minds would like to know.

Initially, without tubes, think you are making sure you have close to the correct voltages at the proper places. If you set B+ voltage to 400VDC, you should get the readings listed in the chart on pg. 52 and layout. B+2 and B+3 are on the schematic , but I'm pretty sure B+2 VDC is measured at the end of 47K power resistor above the last 33uF cap. Don't forget to plug the amp up to a load(speaker) when you test with tubes in.

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"The only problem with being retired is you never get a day off"

Yep. Definitely need to make sure a speaker is hooked up before installing the tubes. I made up a cable with a 1/4" jack on one end and two terminals at the other end to do this with my first build. Are your voltages still the same as they were before or did you figure out what was going on?

The VRM controls DC voltage after rectifiation, not AC in any way!

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

Oops! Thanks Stephen.