Bad choke?

[KE6DF]

I have a big Thordarson swinging choke rated at 16/6 henrys 500ma.

It's a Tru-Fidelity unit so it should be good quality.

Anyway, with my Amprobe DVM it only reads 9Hy.

Typically this meter reads the correct rated inductance on choke -- usually a bit higher given that smoothing chokes are rated for carrying DC.

My question: Is this choke bad? Shorted turns?

I'm moving house and am dealing with moving an overwhelming amount of krap so this choke is a strong dumpster candidate -- if it's bad.

Dave

[W7TFO]

Doesn't sound bad to me.

Maybe try putting a little DC through it while taking the measurement or does your meter do that automatically?

73DG

[KM1H]

Hand helds are notorious for misreading swingers.

Carl

[ke7trp]

I tried to measure swining chokes a few times over the years, the one in my King for example  I could not get a reading on it. If it has no short to case, its probably good.

C

[KE6DF]

Hand helds are notorious for misreading swingers.

Carl

Interesting comment because I have found other swingers where I get readings that seem low.

I'll hang onto this choke.

It's rated at 7.5KV RMS so it would take quite a bit to burn it out.

Plus it's a top-of-the-Thordarson-line unit and presumably was used in a broadcast xmtr of some kind -- and commercial users typically use parts below max ratings.

You never know how much krap you have accumulated until you have to move it....

Dave

[KA2DZT]

I measure chokes with a GR bridge.  Usually get readings close to what may be expected.  Hard to measure chokes to their rated inductance.  They need current through them and you need to duplicate the same test set up that was used by the manufacturer.  The best way to test chokes is to connect it to a TEST HV PS and measure the AC ripple under load.  Then compare the results against other known good chokes in the same size range.  You can tell what chokes work better than others.

Fred

[KM1H]

It's rated at 7.5KV RMS so it would take quite a bit to burn it out.

Id suggest hipotting it before applying any serious HV as even the best of the oldies can deterioate the wire and winding insulation over time.
That RMS rating is with the applied DC plus ripple riding above it and with a real low value input cap it can be pretty high.

Carl