EEVblog #634 - Analog Multimeter Teardowns

[EEVblog]

Teardown Tuesday.
3 classic analog multimeters:
Metrawatt Unigor A43: http://www.haw-hamburg.de/fileadmin/user_upload/TI-IE/Daten/Labore/Elektrotechnik/Bedienungsanleitungen___User_Manuels/UnigorA43.pdf

Triplett 630NA: http://www.triplett.com/wp-content/uploads/2012/11/84-183f.pdf

Simpson 260 XLP http://www.simpson260.com/260-6/simpson_260-6xlp.htm

[kizzap]

Well there is the multimeter shootout for the year over and done with! 

That Triplett was a damn fine looking meter inside

[Bored@Work]

If the label on the Unigor doesn't say BBC Metrawatt, but just Metrawatt, then that particular meter must be from before 1968. In 1968 BBC bought Metrawatt and they became BBC Metrawatt.

That also matches the age of other Unigor meters, the Unigor design series originated in the early 1960th.

So you are looking at a 45+ year old meter, still in spec. and where they did manage to get the pin spacing right - as opposite to that second meter 

[vk6zgo]

What?
No AVO 8?

[EEVblog]

If the label on the Unigor doesn't say BBC Metrawatt, but just Metrawatt, then that particular meter must be from before 1968. In 1968 BBC bought Metrawatt and they became BBC Metrawatt.
That also matches the age of other Unigor meters, the Unigor design series originated in the early 1960th.
So you are looking at a 45+ year old meter, still in spec. and where they did manage to get the pin spacing right - as opposite to that second meter 

Ah, thanks. In that case I'll cut it some more slack!

[MaxTesla]

Hey Guys and Dave

As my Dad owns quite an old multimeter made in USSR, I thought i should share some teardown pics with you

I don't know how old it is exactly, my guess is as it is made in USSR and my dad did his apprenticeship back in 1970, that the meter must be at least 40 years old.

Hope you are enjoying the pics
On the back side of the meter there are some instructions how to measure stuff, the input sensitivity (DC range 20kOhm/V ; AC range 4kOhm/V) and the burden voltage (DC 0.4V ; AC 1.0V)

I am sorry for the bad lighting condition of the pics, my workspace is in my basement

Regards,

Max

[david77]

Here's a scan of the "RIM Electronic 1976" catalog pages concerning the Unigor A43 and its bigger brother the Unigor 6e.
The A43 is still a very common meter on ebay or on local flea markets, the 6e is much rarer, wich is understandable as it cost double the price of the A43. Note that one is sold a Metrawatt and the other under the Goerz brand name. After seeing Dave's
teardown it is clear that the same construction style was used on both these meters. Not only the outside looks extremely similar.

I do have a 6e in good condition, it's my goto meter whenever I want to use an analog meter. From a modern POV the build quality might look atrocious but considering that these meters were probably designed in the 60ies and were probably the first generation using PCB's, one shouldn't be so hard on them. They do still work after 40+ years, to me that is a sign of quality.

Can anybody shed some light on how BBC (Brown Boverie & Cie, not TV station), Goerz and Metrawatt were involved?

PS: Sorry, scans are in German.
PPS: Just looking at the technical data for the 6e I noticed it mentions the burden voltage in the amps ranges. There wouldn't be much point in Dave's µCurrent if modern meters were that good.

[RupertGo]

I think the 'trimmer resistor' at 26:10 is a compression trimmer capacitor; I remember tweaking banks of those things when aligning old communications receivers back in the day. I guess that's C3 in the Triplett circuit diagram, but I can't make out what it does - something to do with the capacity measurement? Which looks a lot of fun - whamming 110 VAC mains voltage across a capacitor divider to work out the DUT! That's a very macho way of doing things: none of that weedy internal oscillator nonsense for Real Engineers...

[david77]

...
Which looks a lot of fun - whamming 110 VAC mains voltage across a capacitor divider to work out the DUT! That's a very macho way of doing things: none of that weedy internal oscillator nonsense for Real Engineers...

The ICE Supertester 680R does that too. It's supplied with a 230V mains lead for capacitance measurment. Always made me kind of nervous...

[Cottees]

I have a Jayem JK-20K. It was my grandfather's. I think it was Aussie built.

[Towger]

What?
No AVO 8?

I have a broken military version, I was planning to send Dave soon. It is old and crusty just like how Dave likes his vintage electronics. The smell of musty old electronics off it would take your breath away :-)

Only problem is the postage is about 50 euro...

[Radio Tech]

Nice tear down Dave.
I love old meters.
Here are my two Simpon meters. The one on the left is a series 6PM (1973 vintage). On right series 6XLPM (1978).
Both of these meters have the mirror.


The third one is a Simpon wanabe, my old Micronta 22-220 (1978??) From when Radio Shack was a real electronics place!
Link to Micronta
http://www.radiomuseum.org/r/radio_shac_micronta_electronic_mult.html

[EEVblog]

I think the 'trimmer resistor' at 26:10 is a compression trimmer capacitor

So it is. Completely missed that in the schematic.

[EEVblog]

The third one is a Simpon wanabe, my old Micronta 22-220 (1978??) From when Radio Shack was a real electronics place!

I have one of those and was looking for it before the teardown but couldn't find it!

[Radio Tech]

I have one of those and was looking for it before the teardown but couldn't find it!

Funny 
I was just about to hit post on the two Simpson's when I remembered I had the Micronta. So threw it in as well.
China quality at it's best.

[Stonent]

I've got an early 80s Micronta with the range doubler. It has a nice hickory smoked .46 ohm resistor inside with the wires exposed from when I tried to measure a car battery on the milliamp or ohms range accidentally.  The video explains the unobtanium in these resistors.  I could get an smd resistor in that value 0805 I think but it was 6 or 7 bucks.

[WackyGerman]

Hi Dave ,
thanks for the interesting teardown of good old analog stuff . So here is my ABB Metrawatt Metravo 4 s with rubber holster , built in 1976 . It s a little better than the unigor and it has 1333 Ohms/V

[quarros]

That Unigor meter to my knowledge had at least two different version/manufacturer. One is made by Metrawatt and the other is by Ganz. I dont know who copied who but aside from the case of the meter, the inside of the two was very different (2 board construction to 4).
Interestingly even now the Ganzuniv is a crazy expensive equipment, a refurbished one is cost at least 420 AUD



Pictures of the inside:
http://regimuszereklhanzi.5mp.eu/kepgaleria_nagyitas.php?azonosito=regimuszereklhanzi&oldalkod=ErgPrYxc0Y&kepkonyvtar=&kep=06..jpg

Ganz: http://en.wikipedia.org/wiki/Ganz_Works

[linux-works]

I bought one of these just a week or 2 ago:



and even a 2nd one since I liked it so much.  I'll open it open it up and take some teardown pics of them.

they are nice cute little meters.  still a current model even after 50 or so years!

[Radio Tech]

I bought one of these just a week or 2 ago:


and even a 2nd one since I liked it so much.  I'll open it open it up and take some teardown pics of them.

they are nice cute little meters.  still a current model even after 50 or so years!

I have one almost the same. It is the 310-TEL
These were designed for the telephone repair man. Voltage only goes up to 300 volts AC/DC.
 On the top is a place to connect the lanyard  to hang yourself with.  Also has a polarity switch on the side.
I like mine and use it often.

Thanks for sharing.

[linux-works]

the polarity switch is nice.  neither of mine have it.

one that I bought came with the ac clamp.  I can't seem to get my clamp to read anything, but maybe I'm not using it right.

there are some that are marked as 'bell system' and some that were even made and marked with 'ibm', sort of how fluke made some of its handheld dmm's for ibm.

the little mighty-mites are not light   when I hand mine to people, they are always surprised at how heavy it is, for its size.

[Radio Tech]

the polarity switch is nice.  neither of mine have it.

one that I bought came with the ac clamp.  I can't seem to get my clamp to read anything, but maybe I'm not using it right.

there are some that are marked as 'bell system' and some that were even made and marked with 'ibm', sort of how fluke made some of its handheld dmm's for ibm.

the little mighty-mites are not light   when I hand mine to people, they are always surprised at how heavy it is, for its size.

Good info.
I agree, these things feel like bricks.  Can you imagine having this hanging around your neck all day? When I worked in the mobile communication field and had to go out and service 800 MHz trunked radio systems the Tel-Co folks would always meet me at the tower sites with these things hanging around their necks.  I was really surprised how much they weighed.
The polarity switch was a nice feature also.

[WackyGerman]

yes they feel like bricks , also my metravo 4s . but my greenlee dm-a 830 is really huge and heavy too . i think the cat IV 1000 V rating is the reason for it . it s built really solid , could be used also for self defense 

[elliott]

The Triplett's protection diodes are in a single package, it is that gold leaded brown component on the back of the meter movement. I have a pair of 630As, I'm jealous of the NA's range doubler. I also have a 630-PLK with the overload reset, but it was beyond repair due to corrosion of the range switch.

You can hurt a Triplett, I'm not sure how because it was done before I got it, but you can burn those unobtainable precision resistors.

[Thilo78]

Dave, as I just commented on YT:
If you don't like the Unigor, I'll be happy to give it a caring home 

I have my somewhat-80s Unigor A43 (manufactured in the time when Goerz Metrawatt was part of BBC) and I love to work with it.
I saved that one from the junk bin in the education lab at ABB, when I was a freshman with ABB in Mannheim.

It would only need a little adjustment. Still have to figure out the bunch of pots to adjust it. 

Greetings

Thilo