AVO Multimeter survey

[noble kiwi]

Universal Avometer Model 7 MK. 2. S/No. 91867 - A - 1063.

[pmmunro]

Phil,

I can understand that you would not want to open up your meter if you don't have to. I have an original Avometer from around 1924 which still has the inspector's seal on one of the movement front-plate screws. It is also still in calibration so I fell I can't open it up despite wanting very much to study the construction, which is why I have been looking for another meter, or even a movement for several years.

I would expect that the damping on the block magnet type of movement is heavier than on the horseshoe type. When I can find the time I must try to make a comparison of a few Model 7s to see if this assumption is valid.

Kiwi,

Congratulations on another Avo acquisition! You do realise that there is no cure until the house begins to seem too small for all these meters?

PMM

[Antlong]

Hello all,

I'm not sure if this will help or not; we visited the Museum of Power, Hatfield Road, Langford, Maldon, Essex CM9 6QA , 01621 843183.

They had a couple of AVOs in a Perspex display case. At the top of the case, not over-well lit for my purpose at least, and they were about to close. I managed to get some wobbly pics of the scale areas as that was the only way I could get the numbers!

One was 74369-C-558 and the other 1357 2 (or Z?) 9949-A-353. Idiot, I forgot to note Model Nos but as I say time was very short.

Hopefully this might help, otherwise they were a friendly lot and I'm sure they'd look closer for you. A good place to visit, especially on a steam day.

Regards Ant

[pmmunro]

Ant,

If your pictures show any reasonable part of the scale plate we should be able to identify the meter.

PMM.

[Mooly]

AVO 8 mk 5 serial number 05071 8V/3/78

Bought when I was just starting out in electronics and seems within spec.

[terrapindundee]

Avo model 40, on the meter scale - "Patt No. 3284-150", Avo label on the right side of the case - "Serial No. 8163 10/2/73".

So is this meter made up from bits of two others ?, it seems to work OK.

[pmmunro]

Terrapindundee

The number on the meter scale is a part number for the scale plate. At this date, Avo were using a set of scale plates with different "scale shapes" (linearity characteristics). The correct scale plate, from a range of 10 or 12, was selected to suit the movement characteristic. There is usually a single or two-digit number at the bottom centre of the scaleplate showing which characteristic it fits.

Earlier meters were individually hand calibrated by comparison with a reference standard meter. Only the scale arcs and the figures were ready printed; on the earliest meters, even the figures were hand written. The cardinal points were set directly and the intermediate radial scale lines ruled in by hand using a goose quill and a proportional pantograph. On many scaleplates it is possible to see the light centre punch marks above the cardinal points showing where these points were set.

As you will have worked out your meter was made in February 1973.

PMM

[Chipmunk]

I have an Avo 8 MkV, with no hint of a serial number anywhere!

Nothing on the scale, nothing on the back instruction panel, and nothing that looks like an AVO serial inside either.

Came to me via a clearance auction for I think about a tenner. Works perfectly on all ranges, in agreement with my Fluke25 (also from a clearance auction, and calibrated the previous year) to within 0.5% on all comparable ranges.

The only damage is that the red/black terminal caps are missing, but that's easily fixed, I have some of that 'mould it at hot water temperature' plastic, ideal use for it I think, it apparently can also be coloured easily with powder pigments.

This one, in addition to my Admiralty model I entered earlier in this thread, will become my 'workhorse' as it's so accurate, and clean.

[Geoffrey]

I have four of the beasts.
In order of age, I think:
8MkII - 65677-c-957 A complete wreck with broken case and movement stuck. Most other internals look intact if anyone wants spares.
7MkII - 81116-A-959 Good working order in a nice wood fitted case. I use it occasionally.
8MkII - 115481-C-1160 My favorite, in excellent condition and occasional use. It came, from a boot sale, with original purchase documentation, costing £49-19-6 on the 13th of December 1960 from PC Radio, Shepherds Bush. Now resides in a nice leather case donated by the following one.
A military one carrying numbers 03803, 8V/11/77, 6625-99-620-9572, one or two added marks and inscriptions. Sadly it's taken a heavy knock and the movement is u/s. Could be a spares donor, including case which is excellent appart from inscriptions and labeling defacements.

[Paul Adams]

AVO 9 mk2, Serial Number: 380-1263.

In a bit of a state was this one, as the front glass was loose with screws rattling about inside of the meter jamming up the switches.
Now thankfully all back together and working.
Over 50 AVO’s now, think I may be addicted !

Paul.

[Bryan M]

My AVO EA113, now at the top of the to-do pile, has the serial no.6797 embossed on the back plate. There is nothing on the scale apart from a few symbols and the number 1.25 against each of the dc and ac symbols. It has a black front panel on a grey case.

It's in pristine condition externally except for the loss of the red terminal cover and a loose-fitting battery check switch cover. Thanks to Peter Munro for providing a manual.

Bryan M

[pmmunro]

Thanks for keeping the information coming.

Paul,

I think your diagnosis is correct - if you find a cure, please let me know. I haven't counted recently but certainly more than 100.

Thanks too to Bryan.

If anyone else has an EA113, could you please let me know the front panel colour?

PMM

[Paul Adams]

Hi PMM,
My EA113 is a sort of Bluish shade as shown in photo.

Paul.

[Kevin Hoyland]

Hello.
Avo 8 mk2 no 4773/ 4-7-1973.
Regards Kev.

[Paul Adams]

Hello,
Just acquired this one to the vast collection, an Air Ministry Model 7, but the Air Ministry logo is at the left hand side of the movement as shown in photo, and not at the top like most of the other ones that I have seen.

Does anyone know why the logo is in this position?

Oh and the Serial Number is: 7744-18206

Paul.

[greenstar]

Two rescued: Mk 7's,
71145-24817 and 6741-A-668 M.
One has the little '7' button missing (anyone have one spare?) - and need some leads !

Tony

[pmmunro]

Tony,

I've never seen a Model 7 with the Air Ministry marking before, but the Air Ministry Test Meter Type D is very common. The 'D' has the AM symbol at the top of the scale which is nicely symmetrical but it has fewer scale arcs than the Model 7; there just isn't room at the top on the Model 7 scaleplate, so it had to go at the end.

PMM

[Bazz4CQJ]

One more for the pot is my 8 MkII 134997-C-262. This works extremely well, but looks a little tired. It was in a staff auction when they were closing down (not very long after being "Privatised") the MoD 'Propellants Explosives and Rocket Motor Establishment' (PERME) at Westcott, Bucks.

I also have a Multiminor Mk5, which I use a great deal and which always reads much the same as its big brother. IIRC, I bought the Mk5 as one of a pair being sold "as seen" at a rally for £1; one was perfect, the other was useless - bargain!

Inspired by the thread on Avo accuracy, I'm about to take them in to work and check them against a calibrated DVM.

[murphyv310]

Here is a couple of pictures of the Two Avo 7's I have one is a 1944 model Mk1 and the other a later Mk2

[pmmunro]

Trevor,

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

PMM