Retro Electronics: AVO Universal AvoMeter Model 7

A bit of electronics servicing history - the Universal AvoMeter Model 7

[mbaker]

Within the last hour I have brought a SANWA YX360TRF analogue meter. Analogue meters are unbeatable for certain jobs (try tuning trimmers and ferrite slugs for smoke which is simple on an analogue but near impossible for digital meters). Also the SANWA has a zero centre capability. I have fluke and volcraft for day to day use but would love an AVO. Beautiful piece of kit which would be better off in appreciative hands.

[Malcarper]

There were loads of Avo's at college, back in the late 1960's, when I was studying C&G radio, tv and electronics.
They often got overloaded / blown, by students. The college technician, would then repair them.
I think your find that battery adapter, is made of 'Paxolin'. It's a hard, paper laminated, insulating material.
Again, we used Paxolin a lot at college. Drilled holes in it, then pressed metal turret pins into the holes, followed by soldering electronic components / connecting wires onto the pins, to form an electronic circuit.

[fredmorton]

I still have one of these and would not part with it.
They are so useful and are not prone to strange frequencies as DVM's can be. You can watch small value capacitors discharging which would confuse a DVM. with undulating signals a DVM will be going nuts to lock on to a reading, analogue wins out with a visual display. As for the age, there is a date code on the meter faceplate that is partly from direct view by the case, situated above the Q control.
There is a dedicated site on the web (cant recall where) that gives chapter and verse on these and dates the many variants too. My Mk7 IIRC 1952

[rivets]

I’ve worked for Avo\Megger in Dover for 25 years, and I am company historian. It’s a classic piece of test equipment, sold up until 2008. The date can be obtained from the serial number printed on the scale plate.

[followthetrawler]

this was the first meter I used at work as an apprentice at GEC Traction in Manchester - 1977

[tdcattech]

I have to say that it was impressive how accurate this was and it is nice to read from those huge swinging meters (bit like preferring a speedometer to a digital speed readout in a car) but it belongs in a museum to show how much better things are now.

[nlo]

I still have a Model 7, with the steel back case. I was told it was tropicalized. The steel case has an earthing stud for screening. My other one is a Model 8 Mk 9. Both have mirror scales and are within 1% or better of my Fluke 75. Big and clumsy they are for everyday use, but if your workbench is big enough, just leave them connected all day long to the job in total confidence. A bullet-proof meter from my apprenticeship days, they were the top of for every day use. Good ones are about £50 or so.

[TheRealSasquatch]

A beautiful example of electro-mechanical engineering. I still use my Avo 8 for initial checking on my valve amps - I somehow have more faith in one of these for higher voltages than a modern(ish) dmm.Great video by the way :)

[ericgee]

God, this makes me feel old. My first (work) meter was an Avo 8, the standard for the time.
Great memories. Thanks (I think).

[thephilpott]

On a safety note, early units had a backbox made of aluminium with a black crackle finish. This is all well and good as phenolic boards are glued inside as insulation.... provided no-one has drilled out and replaced the rubber feet and attached new ones with self tappers. The spacial tolerances inside are pretty tight and it is possible to shove a screw straight into a shunt or coil and make the case live when testing.

[jameslamb]

You Philistine, it's a classic piece of "Art Deco" design. I remember using these in school! Lol, that dates me. That manual/handbook you linked to from Wikipedia looked like it was done in the '60s, judging by the print style.

[JerryEricsson]

I have a very old VOM, No brand on it that I can find, just a couple rows of plugs on a red board, a large meter, in a wooden case. When I got it, I pulled it apart and removed some old Winchester brand D cells. They were, of course dead, and at that time, I was working as a Gunsmith and had a table at most gun shows in the area. I put the batteries on my table, and some fellow fell in love with them and tried to talk me out of them. By the end of the show he ended up trading me a very nice little 2 Inch .38 SPCL Chief's Special by S&W. Still have the meter though.

[ParedCheese]

It's all about the nuances of analogue meters. The way the needle wiggles when the voltages is varying can give you as much information as a cheap scope. :)

[thraherxbs]

The top is home made. It is much newer than the rest of the meter. The original Bakelite tops were prone to cracking through the screw holes due to owners over tightening them.

[johncarcher]

My grand dad actually supposedly stole one of these from the navy back in the 1960's and I still have it today!

[Theoobovril]

The AVO here has had a replacement back instruction panel fitted. Thorn took over AVO when Thorn took over Metal industries back in 1967, then, AVO was part of Metal Industries.

[agustinbmed]

And that's how you break a perfectly good case.... you don't pull out... you slide out from the top (or bottom from the looks of yours)

[MrCobo]

My father bought me an AVO Model 7, in its leather case for my 15th birthday (hmm 1972) and working towards my electronics GSE. Still have it and, on occation, still use it for more indepth fault tracing, my newer digital being used for other testing, like fuses and lamps.

[stu]

i used one as an apprentice in the '90s so bought one on ebay a few yrs ago after a few glasses of wine as you do... didn't get leads or a case though :(
 it now resides in my sideboard looking rather good alongside other interesting nick nacks.

[terry]

The AVO 7 had a sensitivity of only 500 ohms/volt so on the 10 volt range it shunted the circuit with 5k ohms compared to 10M ohm for to-days meters or the AVO 8 which is 20, 000 ohms per volt. The AVO 7s were basically designed for Electricians to use (Low impedance circuits) and the AVO 8s were designed for Technicians to use on high impedance circuits. (Radio, TVs etc)