I need a little help before starting up a new amp, PT wiring issue


The schematics are below.

I wired. Black to power/hot and White to neutral. Mains here are 123VAC.
Green/yellow to ground. Green Green per schematic.
I ASSUME yellow black (center tap) and yellow to 5Y3 per schematic.

I have two questions. Is the yellow 5V correct?
If I want higher voltage should I use the grey wire on the primary based on 123VAC mains?




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Joined 2011
Rectifier uses 5VAC, so connect the yellow and yellow to the filament.
Carefully isolate the yellow/black center tap, but do not connect it to anything.
Be aware that center tap is elevated at a high DC voltage.

If you want a higher B+, using the 115VAC tap instead of the 125VAC tap will do that,
but at the expense of lower current. The VA rating does not change.
Joined 2011
Be really careful of the filament center tap, it's hundreds of volts above ground.

Yes, the 5VAC rectifier winding center tap gives 2.5VAC to either end of the winding.
But you cannot ground or otherwise connect the center tap anywhere at all, it has to float.

Cut off the bare end of the center tap wire, and cover the insulated end of the wire
with several thicknesses of heat shrink. No rubber tape, it will fall off in the heat.
Joined 2011
The shrink tubing should go at least 1/2" beyond the end of the wire for voltage isolation.
Then use a nylon wire tie to tightly fix the tubing onto the wire, so it can't ever slide off.
This is a really critical place to isolate properly.