Thordarson Modulation Transformer

[KE6DF]

I have a Thordarson 11M75 modulation transformer.

It's a CHT 75 watter and is the black cube type with the plug connection panel on one side (12 connections).

Anyway, I need to find something to use for the connection plugs as I have none of the originals.

I tried standard banana plugs, and they are too large.

I tried mini banana plugs and they are too small.

Could someone with some of these plugs measure the diameter with a micrometer and post the result?

I'm hoping it will be close to one of the standard wire guages (say 10 or 8 guage) and I can use pieces of single strand wire for jumpers -- or else get some brass or copper rod stock and make some plugs.

I realize this has come up before, but I don't remember anyone posting the diameter of the plugs.

[WA1GFZ]

I think you need pin plugs. They look like a banana plug without the spring loaded sides just a straight pin. Cannon pins would also work.

[Todd, KA1KAQ]

Went through the same search recently. I actually have one of the original Amphenol plugs, basically a pin with bakelite body for gripping. No joy finding originals.

An excellent substitute is the RCA plug sans outer metal clip/jacket. First perfect, the phenolic center insulator seems to handle the HV just fine, and the pin is the same size. You'll not likely need the full dozen as you'll only jumper a few of the sockets.

[k4kyv]

I once used one of those transformers years ago, but unfortunately crapped it out in short order, whilst experimenting with high level speech clipping. As I recall, the large (filament) pins of a non-octal tube socket are the correct size.  If you have a bunch of defunct 807s, 1625s or other tubes kicking around, you might give this a try.  Since  you will probably need at least 8 of those pins, I would NOT suggest destroying good tubes just to salvage the pins. Maybe the brass rod idea is best, or standard size wire (most likely #8 would be correct). Another idea, if you can't find a solid rod or wire that fits exactly, but you can find one that is slightly too large, try reducing its size by rotating the last half-inch or so of the rod against a grinding wheel, then polishing it with fine grit sandpaper until it smoothly but snugly fits in. I emphasise the "polishing" part, because you don't want to scratch off the plating on the inside of transformer terminal with a roughly ground piece of rod.

Todd's suggestion of the pin from an RCA plug seems most promising.

[KC9GMF]

I've used the smaller pins on dead 811's before.

[KM1H]

I've used the smaller pins on dead 811's before.

There should be enough dead Chinese 811 and 572B's to go around the world.

Thats the same tube base used thru a good part of the 1920's and 30's for receiving type tubes such as the 27, 80, 5Z3, 45, 2A3, etc.

Carl

[KE6DF]

Last week I replaced the ice maker in our fridge. Ordered the replacement unit from the manufacturer and installed it.

The replacement unit was intended to fit a few different models of fridges, and included a wire adapter consisting of about 6 in of wire with connectors on either end.

I didn't need the adapter, and so I just took one of the connectors apart and tried the pins.

Perfect fit.

There are only four on the adapter, so I'll need to find some more, but it looks like a standard Molex connector.

Looks like a trip to the electronic store is in order to find some Molex pins.

[w1vtp]

I've used the smaller pins on dead 811's before.

There should be enough dead Chinese 811 and 572B's to go around the world.

Thats the same tube base used thru a good part of the 1920's and 30's for receiving type tubes such as the 27, 80, 5Z3, 45, 2A3, etc.

Carl

Carl

You got that right.  I'm working on my collection of bad chinese toobs.

Al