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I'm building a tramp kit, and I'm to the point where I've applied power. No flashes or magic smoke, so things are looking up. I'm measuring the B+ voltage at the left most 50uf cap, and I'm expecting roughly 400 volts AC. (I'm using 47uf caps, rather than 50uf caps, by the way so I realize the voltages might be different.) What is the 400 volts with respect to? When measuring DC voltage, I get a reading using the chassis as ground. When measuring AC voltage, I get nothing using chassis as ground. However, when I use either of the red leads from the power xformer as reference, I get 330 Volts AC at that point.

What is the reference for measuring the AC voltages?

You should get around 400V DC at the first filter cap, relative to chassis/ground. You shouldn't have AC at that point.

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Great tones come in small glass jars!

Got it. When measuring the DC voltages against the numbers on the layout, I get the following (left to right on the layout):

400->414
29->31
340->337
191->182
***203->154
2.3->2.2

The only voltage that looks a bit weird is the one I noted. That said, I plugged in a guitar and rocked on it. Sounds good in my test run.