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| | |-+  Weird issue -- 5v tap reading 120v -- Bluesbreaker
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Author Topic: Weird issue -- 5v tap reading 120v -- Bluesbreaker  (Read 3746 times)
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« on: December 14, 2015, 12:28:41 PM »

Guys. After more than a year, my dad and I FINALLY built his Bluesbreaker. Got it all wired up and double-checked on Saturday. Went through a little testing procedure, which included measuring various voltages before loading up the tubes. 120 mains coming into primary -- good. 3.15 for heaters -- sweet. B+ -- rock and roll. 5v rectifier heaters -- 120 VOLTS!

I'm using a MM transformer (photos of lugs and guide from Mercury attached). It's hooked up, far as I can tell, exactly correctly. It's a multi-mains transformer. To get 120, you just don't connect the other wires and connect only black and COM (common 0 for the multiple mains options). That's what I did. Black to power switch. COM to N leg of mains input. Just like the diagram.

Called MM -- they said it's an impossibility that 120 is coming off the 5V tap; SOMETHING must be wired incorrectly. I don't even know where to look! As I'm typing, I'm not certain that I measured for voltage at 0 and 5 on the transformer. But I definitely did measure between chassis-ground and 5 as well as chassis-ground and pins 2 and 8 of the rectifier tube socket.

Any ideas? It's wreckin' my head!

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