Power Transformer - Heathkit IG-82 Salvage Operation !!

[TomCarlos]

MEF members...

I came across a non-functioning Heathkit IG-82 signal generator - schematic. The case seems like it is usable for an upcoming project I want to undertake. That will be a different thread some day.

This unit has a Power Transformer with the # 10976526. It also has 54-59.

Input Wires
Red Output Wires - 125 vac, no centertap, unloaded
Green Wires - 7.0 vac, no centertap, unloaded

The unit uses the following tubes:

6CL6, qty 2, 650ma x 2 = 1.2 amps

6AW8A, qty 1, 600ma

6CB6, qty 1, 300ma

12AT7, qty 1, 300ma

(I assume the specs I found are relatively accurate for a given tube)...

So I pull out the abacus, flip the beads, and it looks like the transformer is supplying ~ 2.5 amps on the heater winding.

If nothing else, the transformer would serve as a standalone heater supply? The only thing needed might be a couple 100 ohms resistors to ground?

I found this Heathkit at a local electronics surplus place ($10). I felt like Mike and Frankie doing some digging on American Pickers!!

[Enzo]

I felt like Mike and Frankie doing some digging on American Pickers!!

What, you mean you walked into their door, with the camera crew already there and set up to watch you enter, and the owners pretend to be surprised?

Don't forget the 6v pilot lamp. I bet the thing is good for 3A anyway, they didn't push things hard.

Looks like the doubled up power supply for B+ will make about 300v, that might be useful for a preamp circuit.

Yes, you'd want to add a fake center tap to ground. Heath in this model linked the heater winding to the B+.


I have a Heath IG-82 in my car as I write. It wants to work, but needs attention.

[TomCarlos]

Thanks Enzo...

I was wondering why the connection of the heaters to B+. That is new to me.

[Enzo]

Well, it is quite common to see "elevated" heaters for hum abatement. An old trick is in a cathode biased power amp, they connect the heater center tap instead of to ground, connects to the cathode of the power tubes. It is just sitting there at some useful positive voltage, so we steal some of it.

In the Heath case, elevating the heaters to 88v will surely do that, but I SUSPECT the reason they did it was those first three tubes. The cathode voltages of 90, 104, and 150 volts. Tubes have a maximum heater to cathode voltage. The cathode is very close around a heater, and excess voltage difference can break it down.

You may recall various discussions we have had where certain tubes are not happy as cathode followers for this reason.