[Jim Koehler]

Hi Guys.....
On the bench as I write is the power transformer of a Philco 630. The original transformer has died and went to flux heaven. The replacement, a known good transformer (so far), needed the usual new extension leads and a trip to the painting booth.
What I need to know before installation is the idle current draw on the AC primary side of the transformer. Hooked up at 117 VAC, I'm seeing a draw of 160 ma. (+/- 10 ma.)
Is this number in the ballpark? Unlike new transformers, I know the efficiencies of these older units can vary quite a bit and before I go about installing this one, I'd like to get a handle on whether or not the transformer will be a good candidate.

All ruminations welcome...
...Jim

[morzh]

Sound OK to me.
The basic rule is, if your transformer does no smoke and faithfully converts voltages, whatever current it draws then on the primary is the good current. Otherwise, in case of shorted turns etc, you will either smoke or won't convert etc etc.

The idle current is simply 110V divided by the primary inductance's impedance which is your inductance in H, times 6.28, times 60 (Hz). Say, 1H inductance gives you roughly 370 Ohms which would create roughly 0.3A current.

[Jim Koehler]

Ok Thanks....

The transformer is working in the radio quite nicely.

...Jim