Hoffman AC30

[Iron Rose]

Newb question.
Hammond 270HX has ct on the 5v and the 6.3v
Should both of these be run to ground?

[Glenn]

I have used that tranny in a few of my builds, I grounded the ct of the 6.3v and taped off the 5v ct...only one is needed
. Glenn

[PRR]

The 5V is usually the rectifier +DC output and should NOT be run to ground!!

The "best" use of the 5V CT is to run it to your first filter cap. Instead of taking 1st filter from one side of the 5V winding as we usually do. In theory this gives a few volts less ripple. In practice: Sluckey looked real hard at both connections and any difference was dubious (lost in other effects). If you don't use the 5V CT, tape it off.

[Iron Rose]

There are (2) 100k resistors on the board.
Should they not be used with the ct to ground?

[PRR]

> There are (2) 100k resistors on the board.

100k?? Or just 100 Ohms?

The two 100r are on the 6V feed. Not the 5V for the rectifier.

[Iron Rose]

Sorry,yes, 100 ohm in the heater circuit.
I have read to use the ct or the resistors, but not both.
Just want to clarify.

[PRR]

Keep it simple. Tape-off *both* 5V and 6V CTs. Use the two 100r on the 6V heater lines. Wire the 5V just like Hoffman shows.

In principle you "could" ground (or elevate) the 6V CT, that was commonly done. But if there is a heater-cathode short the current is unlimited, much damage can happen. The two 100r will control stray heater voltage and will limit the fault current, at worst blowing-out 30 cents of parts.

[Iron Rose]

Thank You.