Eico HV probe rating - any guesses?

[KA1ZGC]

I just found an HV probe in my junkpile I forgot I had. It has that unmistakable bakelite smell. It's made by Eico, and has 740 Megohms of series wirewound resistance inside (also with the Eico stamp). It's about 3/4" dia, and about 9" long.

I'm guessing I pulled this from my grandfather's stash, he was the original TV repairman of the family.

I'm trying to decide if this meant for the single-digit kilovolt range or closer to flyback voltages (10-30 kV).

The math wing of my brain is on strike today. Any guesses?

--Thom
Killer Aircraft One Zeppelin Goes Crash

[AB2EZ]

Tom

What it is good for and what it is safe for might be two different things for an antique HV probe.

Assuming that it was intended to be plugged into an instrument (e.g. a VTVM or a scope) with a 10 Megohm input resistance, that would correspond to an intended use as 75:1 voltage divider. I.e. 10 megohms / (740 megohms + 10 megohms).

I would worry about the safety of any HV probe whose condition is unknown. E.g. leakage due to the presence of conducting films that have formed over time, carbon-filled paths due to past arcing, cracked internal insulators, ...

Stu

[KA1ZGC]

What it is good for and what it is safe for might be two different things for an antique HV probe.

Agreed. I would certainly hipot it before I went waving it around high voltages in the real world.

Assuming that it was intended to be plugged into an instrument (e.g. a VTVM or a scope) with a 10 Megohm input resistance, that would correspond to an intended use as 75:1 voltage divider. I.e. 10 megohms / (740 megohms + 10 megohms).

(Smacks hand to forehead) Yeah, I knew it was something simple and sensible. What's the latin word for "duh"? I guess sometimes I really do need to hear the obvious. Thanks, Stu!

Yes, this would have been tied to a VTVM or similar tube-input device, knowing my grandfather, so 10 Megohms would be the right number.

I would worry about the safety of any HV probe whose condition is unknown. E.g. leakage due to the presence of conducting films that have formed over time, carbon-filled paths due to past arcing, cracked internal insulators, ...

Yep, I'll certainly hipot test this probe before using it. What I'm partly trying to determine is a good voltage range for hipot testing. I'd hate to hit it with 10kV if that's just going to destroy a otherwise-good probe.

[The Slab Bacon]

Keep in mind, guys that MOST of those HV probes were designed for testing the HV in older televisions. Which in most cases is much higher than the plate supplies in our transmitters. (at a much much lower current capability). Older color TVs could easily see 30-40KV on the anode.

Clean it up good and closely examine it's insulation carefully and let common sense be your guide.

                                                             the Slab Bacon

[KA1ZGC]

Yeah, Frank... quite likely that's what he used this one for.

He had one of those plastic sliding-rule type of measuring devices for checking flyback voltage (you know, stick the stirrup under the cup and slide the plastic dingus inward till the light comes on). We were spoiled at my last shop and had a real kilovolt meter.

This is your common pointed tip, though. If it were for checking flyback voltages I'd expect it to have a stirrup end.

I got bit by a flyback xfmr once when I was in the trade. 24,000 volts, IIRC. Threw me backwards several feet. No big rush to repeat the experience.

I'll definately be careful!

Tnx, guys.

[KB2WIG]

If you want to bite the bullet...   Surplous Steals of Nebraska has the Manuel

PUB)  EICO-HVP-1 Eico HVP-1 High Voltage Probe Operating Instructions 10.00


klc

[KB3DKS]

The Manual can be found here for free in ziped gif.
  Look under Test Equipment, Eico.

http://www.nostalgiaair.org/References/Manuals/

Bill KB3DKS in 1 Land

[KA1ZGC]

Eico HVP-1 High Voltage Probe

Yep, that's the animal, alright...

http://www.nostalgiaair.org/References/Manuals/

Bingo! Found it! Thank you very much!

Neat site, hadn't seen that one before. Thanks for the link!

--Thom
Killer Agony One Zipper Got Caught

[KA1ZGC]

For what it's worth, it turns out this probe was configured to read 1,000 volts on an Eico 221 with 30,000 volts at the tip. No idea who wound up with the meter. It wasn't me.

So it's got a bakelite handle, and a lucite shell on the hot end. Any recommendations for cleaning solutions that are friendly to both substances (or warnings about ones that aren't)?

[KB3DKS]

  I think I have one myself, or a close equiv.
 Looks like a nasty S&M dildo or something Tesla would have used. Bright red plastic tubular probe with a long pointed metal tip. Blue cable. Will have to look.
 Don't know about cleaning it but I usually use ethenol denatured alcohol and then wipe down with windex or similiar for plastics. Must dry completely!

 For use, instead of the 30:1 divider that it is intended to function as, you could probably terminate it to be a 10:1 in a small utility box and mount a set of banana jacks or a pigtail to plug into a digital meter. Maybe add a neon lamp or two and resistor somewhere to gnd to act as a safety.

Bill, KB3DKS in 1 Land