The AM Forum

What connectors are best for connecting an external HV power supply to an amplifier?
73,
Bill KO4NR

Before making any decisions, I suggest a thorough reading of this thread:
http://amfone.net/Amforum/index.php?topic=44457.0
A lot of good information, as well as a valuable cautionary tale.

[Edited today: my original link would take you to page 2 of that thread, bypassing crucial stuff on the 1st page.]

Thank you!!
73,
Bill KO4NR

OOPS

I also used the ancient pin jacks on my EFJ 500.

(https://photos.smugmug.com/EF-JOHNSON/Johnson-500/i-zqP4wRH/0/d641bf3f/L/HV%20CableCrop-L.jpg)

The stuff I’ve built or rebuilt with a separate power supply, I’ve only used the SHV connectors. Millen connectors or other archaic mis-applied connectors used for multiple kilovolt connections have always scared me, so I don’t use them…

To avoid the issue mentioned above with the HV cable shield being the return/negative line, which can lead to dangerous situations, I use a second interconnect that carries a heavy ground wire as well as the control for the HV supply..it won’t turn on or stay on if that cable isnt connected. I use a locking, line-rated, UL listed connector on this cable. That way, the shield connection is never breaking the circuit unless the supply is already both turned off and control disconnected. There’s no local switch on the PSU to independently turn it on, either.

Ed

KD1SH covered it well with Shane's mishap. Learn from other's experiences, albeit good or bad! RF Parts has those Millen type connectors listed for 7KV @2A. Personally, I wouldn't trust them much above 2KV. Mike, KE0Z has it right. Those HV connectors are a good sub. I need to get some more RG-58 to complete the remainder of my HV connections.

A timely thread.

I'm currently addressing how to get the 2 KV from my HB power supply to my TBW transmitter.   I have a few questions but want to review some other related threads first.  The more I think I know, the more questions I have.

And...the wrong way to do it. Home-brew power supply and amplifier I acquired recently. The exposed 240 VAC terminals alone ought to be enough to give anyone nightmares, but those big ceramic insulators — 4KV at 3 amps! This guy used some good design practice in some areas, but in others, not so much. When you pick up old HB gear, never underestimate the insanity some builders are capable of.

I bought something similar. The guy had a couple of lucite rectangles as safety features. 🙄😬🤪
I was lucky to get 600 volts across hand to hand and staggered backward as I began to black out and got off it. My chest hurt for a month. Not sure why I wasn’t dead, but it was a great cure for thoughtless stupidity. Still worked with much higher voltages and one of my OM mentors showed me once how 4500 volts can jump and arc with no contact necessary. Still keep one hand in my back pocket even when using HV probes…
Call it fear or respect, but abominations like this can kill. Good practice does not take much more effort, but not being fried is good motivation…😉

7-16 DIN connectors.  Rated for HV, cheap on the Bay.

They come in chassis or cable usage, male or female.

Hard to kill yourself with them.

73DG

While recently unscrewing a Millen connector, as it was turned, the HV wire just came out of it. Apparently the solder connection in the end had broken loose. over time. Mainly pointing to connectors that do not use some sort of force to retain the wire/cable inside the body.

Egads! 4KV at 3A! That is 12 KW!!!!!

It's a big Peter Dahl Hipersil transformer, with encapsulated rectifiers and oil filled caps. Very nice build other than the exposed terminals. It runs a pair of 8877's/YU158's.

Life's too short for QRP.

73DG

I did a TBW about fifteen years ago and have a video of it over on YouTube:

https://www.youtube.com/watch?v=sd4gPNGNYRU

The original design used a weird three pin ceramic plug, the filament, screen and +500 volts all come in on the big Bakelite connect next to it and you can use banana jacks that fit right over the pins to keep that all original. I had a 2-kV power supply that was under the rack that was connected by a chunk of RG-58 with crimp on connectors on the shield and center conductor that was attached to the screw terminals on the filter capacitor in the power supply and connected directly to C327 or C336 on the HV side of the plate tank and did not attempt to use the original HV plug on the bottom of the transmitter.
Are you going to use screen modulation like the original design or high-level modulation?
Do you have the center section?

Ray --

I'm starting a new thread in the Military Radio section and will answer your question there.

Under 2500VDC I've used teflon UHF connectors with great success. Of course you gotta use a  suitable wire with it.