AVO Multimeter survey

[Station X]

One off topic post moved to a new thread here:-

https://www.vintage-radio.net/forum/...ad.php?t=77538

[Paul Adams]

Hello all,
Santa’s been early and left me with another AVO, this time it looks very much like this has never been used, as it’s in mint condition.

It has a ‘D’ cell holder that I have never seen before, I thought at first that it was home made, but after looking more closely it appears to be well engineered very much like the meter, and probably made by AVO.

It came in the original AVO cardboard box, together with the packing slip, and the original user manual. ( I am more excited about these )

The serial number is: 77907-A-1158.

Paul.

[Brian R Pateman]

Recently acquired AVO Model 8 MkIII.

Serial number 6XXXX 1167.

A very nice instrument and the calibration looks pretty good from a quick check.

[noble kiwi]

Just to hand a model 8 Mk. V, which looks undamaged and all original and is so far testing OK.

SERIAL No. 09163, 8V/3/74. It carries a sticker dated 18/1/88 stating, "Serviced and re calibrated by Nortec (Scientific Equipment) Ltd, Crowther, Washington,"

[Craig Sawyers]

Model 8 Mk2, 80646-C-1158
Model 8 Mk3, 71317-1267
Model 8 Mk5, 037876

Multiminor, 77233-1245
Multiminor, 109941-850
Multiminor, later model with metal back, no S/No. Instruction book says "Model 1"
Multiminor, later model with plastic back, no S/No

[Craig Sawyers]

Forgot my most recent baby!

Precision Avometer, 235-466, calibration certificate 20th May 1966.

[jamesinnewcastl]

Following your request, all four of my little beauties are blue mmmmmmmmmmmm! One in long term repair!

(Serial Numbers already logged here)

James

[Still Tinkering]

A little late to this thread, I have a mint Avometer Model 8 in perfect working order, always kept safe within its leather hard carry case, complete with leads, croc clips and probes clipped in the top.

Ser No. 51913-C-1056

Originally purchased by my father, it now resides with me. Batteries installed and put back to work over Xmas for test work on a Bush BP5 I intend restoring.

Kevin

[pmmunro]

Thanks everyone for keeping the information coming. It seems that many people find themselves tempted to acquire a second Avometer "because it could be useful" and find that soon they have a small collection - or even a big one!

Craig,

If you look very closely at the scaleplates of your Multiminors you may see serial numbers stamped into the paint near the bottom centre. I don't know why Avo chose to make these serial numbers so difficult to see but this style is used on a number of models. However, some later Multiminors appear not to have any discernible serial number.

James,

Thanks for the information about your EA113s. I would be surprised if there are many other people who have four of these. If you know of a source of another, one contributor to the forum is very keen to acquire one.

Kevin,

It's nice to know of well-cared for Avometers. Those kept in a leather case are usually well protected. They don't like cold damp conditions; it tends to corrode their brass bits and, in extreme cases it can damage the movement. I find it difficult to understand how anyone can be so uncaring as to treat any kind of precision instrument abusively.

There used to be an advertisement for Parker fountain pens to the effect that one of their pens was the only possession likely still to be around many years, I think it was forty, later. Their case was that your best suit, fine shoes, watch, your car, etc. would all have been consigned to the bustbin/scrapyard but your Parker pen would still be serving you faithfully. My first Avometer, no longer my oldest by a large margin, is just a little older than yours and the only reason that I don't use it more often now is that I have a good few more collected over the years.

PMM.

[Phil G4SPZ]

We enthusiasts who enjoy vintage test gear are fortunate in that we can acquire AVOs and similar high-quality professional equipment for a fraction of its original price. Even if non-working on acquisition, such equipment is frequently repairable simply and cheaply.

The advice must be, 'if you see an old AVO, buy it as long as the price is right' and personally I don't think you can own too many. I have two AVOs permanently connected, monitoring the mains voltage and current to the test bench; one for portable use; and several awaiting restoration!

Can I also take this opportunity to thank Peter Munro and the many others who have made invaluable contributions since this fascinating thread started?

[timewave]

Here are some updates to what I suppose has become my AVO collection!


8 Mk II 128498-C-1061 from the scale.
8 Mk II? 160637-C-663 from the scale.
8 Mk III 83239-768 from the scale.
8 Mk IV 1373.1269 from the scale and 02699 524/170 from an AVO sticker on the case. My parents bought me this one for Christmas in the 60's.

8 Mk V 41247 8V/11/76
8 Mk V 15795 8V/6/74
8 Mk V 04558

40 412223-348 from the scale.
72 164062 from the scale. This one is still in the original box with the warranty card and packing slip.

All except my Christmas present were saved from the skip with my managers' consent.

John

[MrElectronicman]

Here is my latest acquisition. After a bit of a clean up this one works and is very accurate, however there is a problem with the AC range which I am looking in to.

8 MK 11 97680-C-1059

[Andrewausfa]

My fourth AVO 8, recently acquired.

AVO 8 Mk 6 (posing as a BT MMR14C) s/n M90699 5/86

In mint condition with leads, booklet, even the case still smells of new leather.

Andrew

[wave solder]

A few more Avo Numbers for the list.

Firstly an Ex British rail AVOMeter in an alloy case, similar to the heavy duty AVO, the numbers on the meter scale read 159-448. Any idea what model No. this one is?

Secondly I have a Rochester Road Avometer (with Diamond hatching on front panel), Serial No. 1538. A schematic for this one would be most useful as there are a few disconnected wires internally.

Thirdly an AVO Model 7 Serial No. 7941-5860.

[murphyv310]

Originally Posted by pmmunro

Trevor,

Would you like to add the serial numbers of your Model 7s to the survey please?

PMM

Yes please, sorry for the delay.
I'll post some better pics and give you the serial numbers once I feel a little better. (have a stomach bug)

[Paul Adams]

Originally Posted by wave solder

A few more Avo Numbers for the list.

Firstly an Ex British rail AVOMeter in an alloy case, similar to the heavy duty AVO, the numbers on the meter scale read 159-448. Any idea what model No. this one is?.

Hi,

It sounds like a version of the Mark 5, as shown below plus the circuit.

Paul.

[wave solder]

Originally Posted by Antony_G

Hi,

It sounds like a version of the Mark 5, as shown below plus the circuit.

Paul.

It is not that model I am afraid, there is no cutout and the two position switch is also lacking. picture attached.

[pmmunro]

Wavesolder,

Congratulations on your eBay purchases - I'm very glad that they have gone to a good home. Thanks for the detailed information on the purchases. The seller stated that the case of the Railway Signaling meter was bare aluminium. Does it look as though this is its original condition or has it just lost its paint? It may originally have been wrinkle finish black.

Send me a private message and I will return a diagram of the DC Avometer.

Your British Rail Heavy Duty Avometer is just that. The HD design was comissioned by the Great Western Railway around 1947 but I understand that the first deliveries were not until 1948. Certainly my GWR HD has a 1948 serial number. Probably neither the GWR or ACWEECO thought that those socialist upstarts would actually dare to carry out their threat and nationalise the GWR!!!

The original design really was heavy duty as you can see from yours. Both the front panel and case are cast aluminium. Unlike other Avometers, the marks (versions) have a simple logic - there really are five distinguishable stages of developement. (In fact a sixth was planned, but I don't have enough detail to know if it was a complete redesign or just a further development and I don't know if it was ever made).

Two types of Heavy duty Avometer were made; the Railway Signalling and a Commercial version, with different ranges. The movement is more closely related to the design of the Universal Avominor than the full-size Avometers, with a cut-out incorporated on later marks. The ranges of the two versions are different; I can post a table based on my sub-collection if it is of interest. The earliest marks may only have been available in the Railway Signalling version.

The later versions of both Railway Signalling and Commercial meters had a Bakelite front panel and Bakelite case. The case was definitely a weak point and most that are still around are cracked, some quite badly. In this respect, they do not live up to their name, which implies an ability to withstand a heavy duty environment.

I have been told that short stature electricians commonly used their Avometers as blocks to stand on to reach high objects. Maybe the original cast aluminium version was designed for testing block signalling.

PMM

[wave solder]

Hello Pmmunro, thank you for your very concise reply. The BR heavy duty AVO is painted and not bare alloy, the finish is certainly original and is a light grey hammered finish. Any further information is certainly of interest. It is the first one of its type that I have come accross.

Out of interest how many types of model 7 were there, as I have one with power factor sockets at the top more like a model 40 and one without the sockets.

[pmmunro]

"Officially" there was the Model 7 and the Model 7 Mark II, but this is not really a true representation of the variants.

The original Model 7 (1936) had a horseshoe magnet and was replaced around 1948 by a version with an alnico block magnet. The power factor sockets appeared on some variants around this time, presumably as an option which the customer could specify.

In 1956, the knurled knob terminals were replaced with red and black sockets which could accommodate either hooked leads or plug-in ones. At this stage it became the Model 7 Mark II. The Mark II continued to develop with minor, progressive internal changes until the late 1970s.

I think all later Model 7s had power factor sockets.

Send me a private message and I will return the DC Avometer diagrams and further HD information.

PMM