Hi all. I have an AWA 712C 5-valve radio. The filter choke L14 (on the schematic) is measuring on DMM 9.6 K-ohms & 13.45 Henry's, no open circuit or down to earth.

The specs indicate it should be 1000 ohms, stock Code-TU17 but gives no inductance value or any details on the unit.

The shape is similar to a small metal encased iron core transformer but a coli, ( 63mm x 52mm x 20mm ) with two mountings. It appears to have gotten very hot over it's life.

Can anyone explain to me what this means please, i.e. do I need to replace it, test it if so, how do I test, can I use another type of filter choke?
Where can I but another similar type from?
Thanks
Paul.

Hi Paul,
These chokes cannot really be measured with a multimeter.
The 1000 ohms quoted in the specs are ohms impedance not ohms resistance.

Chances are its OK and even if not will show up as the repair/restoration progresses.
These filter chokes often get very hot, especially when the radio is old, has leaky caps and out of tolerance resistor's,
All contributing to excessive current being drawn through the filter choke.

To start with check/replace all electrolytic capacitors and paper capacitors.
Then fire up via 100 watt globe in series with radio.
Then measure voltages, especially either side of the choke.
With a little luck it will go.
JJ

Welcome Paul!

That's a lot of henries and resistance for an ordinary radio filter choke, maybe it was a substitute.

With 9k resistance, yes, I'd expect it to get hot.

Not an easy item to come by these days.
But you can, if you are also replacing the electrolytics around it, substitute it with a 1k 10 watt resistor and increase the 2nd filter cap to, maybe, 47μF, to compensate for the lack of "filtering".

Don't do this with the other cap that's on the rectifier cathodes, leave it at max 10μF. Higher than that will stress the rectifier valve for no benefit.

Try to dress (position) the hot resistor away from the electros.

Ian

Filter chokes in this application were typically in the 10 to 15 Henry range at currents in the range of 50 to 100 mA. Looking at the specs of a couple of manufacturers, the DC resistance of these was 300 to 600 ohms, measured when cold. Your choke is specified at 1000 ohms, a bit higher than the average but not wildly different.
Your choke measuring 9.6 K ohms is much higher than I would expect. Maybe, as Ian suggested, it may be not the original.
I would be inclined to try replacing it with a 1K resistor and see if the HT voltage is as expected. It is going to get hot and I would use 2 X 2K 5 watt resistors in parallel.
Harold

A second idea is a panel mount resistor perhaps on a side. Have used.

9.6K sounds too high; Possibly cooked.

I would If possible try a pure DC analogue ohm meter and make sure your fingers are not part of the circuit.