Resuerrecting Unigor 6e

[TAMHAN]

Hello Folks,
nice to finally join the forum after reading around for many, many years. Let's get to business: I am, as of today, the proud owner of a vintage Unigor 6e, which I got off a greek fellow who got it from a training academy.

I took it apart and found out that the mechanical meter works, but that the electronics seem to have an eeker. The meter had some "rough times", as it was obviously taken apart once for an exchange of one of the banana plugs (red instead of black). After a few hours of cursing and getting help from el girlfriend, we now have the meter so far that it:
a) reflects on battery capacity
b) shows +inf when in resistor mode
c) shows a zero-ish value in all other modes

Our main issue is now - in addition to the non-zerping -  this, that the meter always sees a "phantom" resistance. So in the highest resistance measuring mode, we are always getting 200 kOhm, even if the clamps are perfectly open.

We tested the resistance measuring mode by attachng an external voltmeter: all the lower ranges get the proscribed voltage, while the highest one is limited to 20% of it. When measuring the internal resistance of the voltmeter, by and large, the internal resistance looks good as seen from an ohmmeter attached across the Unigor under Test.

Ideas, anyone? If yes, big thanks!

[TAMHAN]

Update: this multimeter, obviously, is sexist towards males.

My GF partially tore it down mechanically, reassembled it and suddenly the R modes seem to work again.

Now, just the zeroing remains...

P.S. We just wired 10 Bucks to some Austrian fellow who has the "big" service manual. We expect to get it, and will probably post it here when we can.

[jeroen79]

elektrotanya.com has some manuals for the unigor 6e as well.
Free but limited to 2 a day.

[Balaur]

Good luck on your resurrection.

(By the way, is there any link between this model and the Russian 4313/4315?. The form factor is similar)

I've recently restored my father multimeter (a French VOC 40 from the '70s that I've broke when I was 10 or so). I've deeply enjoyed the project, and the multimeter is now usable, but gee, current digital multimeters are so much better in many ways.
The best characteristics is the AC response. The meter is still able to measure AC (or at least, indicate something) at quite high frequencies (hundreds of KHz).

[TAMHAN]

Hello,
thank you so much for your kind wishes.

First of all: I checked the ElektroTanya manuals, which contain much less data than the full repair manual which I bought (and have here, cough cough). So if anyone of you has an eeker with a 6e, tamhan at tamoggemon point com is your friend.

As of now: the zeroing still doesnt work. But the manual has given me a few pointers which I will pursue on.

In the meantime: I will post some pictures of the 6e, no issue if you guys want. But I am not sure whether it is similar to 3p and so on: the 6e used a taut suspension measuring system, which, according to Ganz Instruments Ltd, was an "all Görtz" affair.

[TAMHAN]

Some updates: looks like the Greek who modified it was not an idiot, but was playing some obscure angle which I dont understand yet.

But, as you asked for pics. The first thing, which to me, looks like a common issue is the connection on top of the Unigor 6e relais, which I - blindly - resoldered as shown. The service manual makes no mention of that, and since I dont have pics of a known working one... ;(

[TAMHAN]

And, our current eeker. D2's "little foot" at the bottom touches the shield, thereby reducing the measured resistance. Proposed fix by el annette: overhead foil.

Out now for a hard round of shopping, will report in again as I get home and have applied the fix.

BTW: we decided that our Unigor, as it will never be moved, will no longer be fed with batteries. instead, we will use a simple power supply along with some caps...no always recharging crappe, less leaking crappe, and so on.

[TAMHAN]

Just in case, why we repair the Unigor: we also have a 34401A in the mail (used, badly battered but working unit). We want the Unigor for two reasons:

a) If I am drunk, I tend to distrust most meters when measuring resistances from our badly battered decade (full of chaos). Unigors, being analog, are, um, "more trustworthy"

b, more importantly) The 6e is SUPER accurate, down to 1 yA and 1mV. Thats why we have the little bugger: its insane accuracy allows us to use it as a "shabbesgoy" for repairing other meters (HP, I am looking at you) and it can also be used on MSP430 circuits.

[TAMHAN]

Hello,
and we have, once again, reached the point of needing some advice.

The remaining error clearly points to a capacitor being blown. In the manual, it is described as:
Tantal Electrolyte Capacitor, produced by ROE
3x100 yF, 3V ETP3

Now my question is: the part looks like a normal electrolytic cap to me. If I buy a 300yf SMD tantalum cap, will this also work, or do I really need to buy three 100yf and connect them in parallel?

[coromonadalix]

https://elektrotanya.com/unigor_6e_6ep_multimeter_sm.pdf/download.html#dl