View Full Version : Emerson 571 Ballast Resistors


Chris K
05-22-2025, 01:27 PM
Has anyone tried to reproduce one of these? There are two 10 ohm and three 75 ohm resistors in it but I can't find their wattage anywhere in the documentation. It's only listed in the parts list as "Ballast Tube" and in the schematic by pin out and resistance.

Yamamaya42
05-22-2025, 01:34 PM
If anyone would know, it would be bandersen. :D

He prob did a few of them. :yes:

Chris K
05-22-2025, 01:49 PM
No doubt. I know he's done similar ballasts for the Motorola VT-71 sets in fact, I copied his design when I restored mine.

bandersen
05-22-2025, 01:57 PM
Not yet, but I expect I will someday.

I'd conservatively estimate 250mA of current. Then it's current squared times resistance.

0.25 * 0.25 * 10 = 0.625 W
0.25 * 0.25 * 75 = 5W

I'd double those for a safety margin.
2W or 3W for the 10 ohm. 10W for the 75 ohms

Chris K
05-22-2025, 11:55 PM
Got it. Thank you so much.