Early Model EICO Model 232 VTVM
 

Hello everyone, yesterday afternoon I picked up an early production run EICO Model 232 VTVM for $10 on Facebook Marketplace that unfortunately is missing its original probe, but otherwise seems to be working.

My question is, I found some modern reproduction probes for this VTVM on eBay for $37 and free shipping and I wonder if anyone on here has any experience with those probes and if they are worth the $37. Also How do these work compared to a modern DMM?

Also is this the piece of equipment they refer to when they talk about using a VTVM in the Alignment instructions for old radios in your old Riders and and Sam's Manuals? If so, how do you hook these up to do those tests?

Thanks, for your help.

See pictures below.

The Eico VTVM came with an Eico Uniprobe, that you could switch out the 1Meg isolation resistor. The DC range requires that resistor in series with the meter. The AC and Ohms range doesn't require a series resistor.
I have a Allied Knight-kit which used two separate probes. I ended up buying a Eico Uniprobe for it.
For the most part, all the VTVM's of the time, shared the same circuitry.

Since you didn't link to the probe on ebay it would be hard to comment on it.
Most modern DMM use straight through probes. They load high frequency signals too much.

Sorry about that the link to the VTVM Probes on eBay is listed below:

https://www.ebay.com/itm/232269025972

The probes are custom made to replicate the 2 probe VTVM probe setup that was used by Knight and others (one probe has the 1 Meg resistor and one doesn't), and the person who made these probes, and is selling them said he tried them out on all of the different types of VTVMs including the EICO and he said they worked on all of them.

I was just curious if you were familiar with this seller and his products and if any of you guys had used any of his stuff or not and what your experience was with it.

By the way it sounds in his description, it sounds like he's an old electronics technician or electrical engineer that was trying to make use of modern parts to recreate a commonly missing part on your old VTVMs and other old test equipment and possibly might be someone who is a member here or at AudioKarma.

I won't comment much on the price, I guess everyone is entitled to make a buck.
The buyer has to decide whether it is worth the price. I would just build my own. It isn't rocket science. If you don't have the skill, patience and understanding to make your own I wonder how someone would be able to fix anything.
That being said, this is not a replica of what the original probe was like. The original probe would not be double headed. With the double probes (which are not switched) the same voltage would be present on both probes when you use it. That means when using one probe you have to be careful what the other probe is touching (might be the chassis, might be something that would be damaged, might be you).
If you click in the guys picture, lower down on the page, it will bring up a bio.

I didn't say that it was a replica of the one that EICO used, I said it was a replica of the one used on the Knight Kit VTVMs, and that the seller of the probes said that it would work on the EICO units.

No. It would be a hard pass from me paying for 2 probes that you cannot disconnect and use seperately.
Not to mention, if you wait long enough you could get a whole VTVM with the probe for about the same price.

VTVM's get weird with RF and capacitance and it makes the meter move just putting your hand near it without the ground lead grounded.

I have the Eico uniprobe and all it is is a 1 meg resistor and a direct . There's a front section that you twist a half a turn and you can select direct, or through the 1 meg resistor.

The original Heathkits were wired the same but they just had a small slide switch.

If I was in a bind and didn't have a probe I would just use 2 regular probes with 1 having the 1 meg resistor. But I want them seperate and not interconnected.
I done this for a while till I was given the Eico probe in box of parts one time.

If you're not to concerned with originality you could also swap out the old microphone connector for a 1/4" mono jack. Like the ones used on guitar amps.
Way cheaper to get ahold of.

OK well I've been looking over at places like Mouser and Digikey to see if I could find the parts there I would need to make the probes to get this VTVM going and I'm not having much luck I was thinking I could try and convert the old Switchcraft mic jack to a BNC jack and use a couple of generic BNC test leads that I could rig one of them up with the 1 Meg resistor that was required for the DC Range and have one without the resistor for the AC and Ohms setting, they would of course be two separate cables that would be swapped out as needed, but all I'm finding as far as BNC test leads are ones that have the positive and negative (black and red clip leads) together on one test lead cable and I'm not finding anything that has just one clip lead on it (just the red clip lead).

Any ideas as to where I might find something like that?

OK so I found an original EICO Uni-Probe for sale on eBay but they want $57+ $5 shipping, plus it has a funky 2-pin plug that looks a little bit like the old switchcraft mic jacks but its not (it's one of those old CB/Ham Radio Mic Jack Plugs), so I wonder if its from a little newer VTVM than mine is, or perhaps a kit version of this VTVM? :scratch2:

See Link Below:

https://www.ebay.com/itm/29451291820...8AAOSwk3xhgBaV

Is $57 a reasonable price for one of those probes or is that person asking too much?

That is not an EICO uniprobe! It's an old scope probe.
The Uniprobe has the front barrel that turns to select AC/Ohms or DC with a 10Meg resistor in series.
My Uniprobe cost less than $10 USD in the early 60's. :thmbsp:

This is the uniprobe.
Like diesseljeep says, the front barrel (white part) turns a half a turn.
AC - ohms on one side, DC on the other. The red dot is a indicator on what setting you're on and it drops into a V shaped notch to keep the position.
They look like this.

Mine is a lighter grey, the early ones were black and red.

https://i.postimg.cc/G3k0j6q0/eico-2...1490207240.jpg



Before I would go to BNC I would go to 1/4 phone plug. It's far easier for mounting nice flexable wire of any size to and easier to service. Also if you're fitting your ground lead on the plug I think you'll find the BNC a tight squeeze.

This is the way my Heathkit has been set up since I got it 15 years ago.
1/4" phono plug and a banana plug for the ground.

I like the seperate ground cause I can change from a probe to a alligator clip any time I want to without any changes to the uniprobe.

Well then it looks like I might be looking for quite a while then because the only thing I'm seeing related to the EICO Uniprobe is VTVM's that have the uniprobe attachment already with them, and I don't want to break up some VTVMs that had been together for all these years.

I bought my Uniprobe to use with my Knight-Kit VTVM. I seemed like it would more convenient than the two simple probes that came with the kit. I used the separate ground lead that came with the meter.

Well I found a manual for the uniprobe over at the BAMA and according to the manual the uniprobe came either pre-built or in kit form, and the one in kit form didn't come with a connector plug so you had to supply your own plug which would mean that you could use any type of plug you wanted whether it was the old switchcraft mic jack, or 1/4" mic jack or an XLR style jack.