AVO Multimeter survey

[Barnmead]

Mine are all 500 Volt models, all apart from one 1946 have a red flag on the meter needle. It does not seem likely that it has fallen off as the needle would not balance correctly. The others are similar to yours.

[The Philpott]

Post 2679 and 2681

Hello Richard (and the others),
I too have noticed the U legend in the corner of the (Universal Avominor) Model 1 scale plates, there appear to have been at least six as i have one which is marked U6. They are, i believe, scale-shape markers.

The Model 1A scale plates i have are marked in a different place, near where you would find the serial number. The markings i have seen are 'Type 3A' or 'Type 4A'

Even the Type E has this type of marking, examples being E3, E4.
I achieved decent alignment and accuracy when matching an E5 movement to an E6 scale plate, which hints that the standard ACWEECO were working to was very fine. I gave this meter to my father, and at some point he put it up against a Model 8 to check it's accuracy; a type of meter he has been using since before i was born. I don't believe he had used an Avominor before and i think it's fair to say he was pleasantly surprised. All this from a wartime meter cobbled together from two donors.

Interestingly, Model 2 Universal Avominors do not appear to have a scale shape marker! My feeling from using the Model 2 is that (albeit with higher sensitivity) it tends not be quite as accurate as a 'happy' Model 1.

The red disc on the needle/pointer (or the lack of it) does have a significant effect on balance of the needle..but it does not seem to throw the accuracy of reading out by too much. I believe that all the Universal Avominors had these red discs on their needles, and those that don't-have thrown them off! I have gone through all my 'minors and equipped any that don't have a disc, with a new one. Partly motivated by not being able to see the needle at certain points on the scale, most specifically FSD, where it is practically invisible!..A pain when checking for continuity!
Dave

[AndyGilham]

Good morning all

Since we are on the subject, I have just received a Universal Avominor Model 1A. this is the earliest one I have seen, with serial number 401-656 (June 1956).

Some of you may have seen this on Ebay, as it was supplied fitted in a wooden box (very snug) that included some sockets. I am not an electrical guy, so not sure what this box connections were used for, maybe a multiplier or for calibration. I took some photos

Interestingly this is marked on the Scale plate as a Model 1A, but the instruction plate is from a standard Model 1. Also the top face of the housing includes Admiralty Pattern 'A.P. 13301', which I know we have seen on instruction plates in the past.

For completion, this instrument has 'Type 3' on the bottom right corner of the scale plate.

Andy

[Phil G4SPZ]

Among other things yet unidentified, that home-made box contains what appears to be a selenium air-cooled finned rectifier and a smoothing capacitor, forming an AC to DC power supply. It looks like it was intended to be powered directly from the mains but you would be well advised not to try it out!

[Barnmead]

Andy
My AD PATT 13301 meter has a brass rather than aluminium backplate, does yours? For shipboard use aluminium would have drawbacks.

[pmmunro]

Originally Posted by Barnmead

Andy
My AD PATT 13301 meter has a brass rather than aluminium backplate, does yours? For shipboard use aluminium would have drawbacks.

Admiralty Pattern 13301 is not a designation I know but Admiralty Models 47A and 48A usually have brass instruction plates. Internally there are other parts which are brass where otherwise plated steel might be used and it is my impression that varnish is used quite liberally to protect parts.

PMM

[AndyGilham]

Originally Posted by Barnmead

Andy
My AD PATT 13301 meter has a brass rather than aluminium backplate, does yours? For shipboard use aluminium would have drawbacks.

Richard,
The plate on the back is Aluminium, so either it was replaced with an old one, or earlier Model 1A instrument still used the Aluminium plate.

[AndyGilham]

Yes another instrument for the Megger collection, this time we have a Model 8 Mark 3 in great condition. Serial Number 82518-768 (July 1968)

this instrument came in a wooden box and complete with leads and all documentation.


I also have a Model 2 coming from Canada.... watch this space!

Andy

[The Philpott]

Andy's Model 1A 'minor serial number 401-656 ties in well with the ones i have here:

132232-1155 (MIMCCO LTD- Marconi Marine)
1951-1156 (ZD03063)
2807-157 (10S^46) -leather case 10S/10614
3367-257 (ZD03063)- leather case ZD03062

This tends to indicate that the start of the production run was inked in as part of the Model 1 production run, before being given it's own number series. (Not an unusual anomaly)

Note also the strong leaning of the production towards branches of the military and their contractors.

My meters arrived with the extra phenolic back board containing (welwyn) component resistors, which effectively removes the cubby hole provided for test leads in the back of the meter (which wasn't very large anyway)
On at least one meter I found these resistors to have been handpicked for very high accuracy- and on that meter they had no trimmers in series.

I would tentatively say that Andy's Model 1 instruction plate has been salvaged from another meter. At least it keeps the dirt out and the battery in.

As regards full size Avometers of admiralty issue, i have noticed they smell quite strongly compared to contemporaries, which might support Peters observation that extra treatment was provided for aggressive environments.

Dave

[pmmunro]

A Heavy Duty Avometer serial number from eBay for the survey: 2484-679. It's an ex BR Railway Signalling version in what looks like very good condition.

Another item of interest is a Model 40 movement with the serial number 403345-243 R which has a block magnet. I take this to mean that it is a post 1947/48 replacement for a a 1943 Model 40.

There are also batches of Model 8 scaleplates for Marks IV, V and 6/7 on offer if anyone is interested. (I hope that it's permissible to mention this here).

PMM

[Sinewave]

The British Railway ones are a nice one to collect. I've only ever managed to find two different regions. I'd like all regions at some point.

[Phil G4SPZ]

Wouldn’t it be fascinating if one turned up from pre-nationalisation?!

I wonder if any of the Big Four railways ever had Model 40s or other Avometers engraved for them, like Marconi and probably others did.

[pmmunro]

Phil,

I have one marked GWR, Serial No.194-448, but it isn't actually pre-nationalisation in manufacturing date since that took place on the 1st of January 1948.

I would think that the order was placed by the GWR once they had seen the prototype of the design they requested and delivery took some months from the date of ordering.

As well as the regional variants, some seem to have been ordered centrally and have no regional marking.

PMM

[Phil G4SPZ]

What a nice item to have in your collection, Peter! I'm sure you're correct in your suppositions.

I hadn't realised that the GWR were actually behind the design of the Heavy Duty model. The GWR seems to have been forward-looking in a number of areas, despite doing a great many things differently from the other railway companies "just because they could". There is a model of Tilley lamp (one of my other hobbies) called the "Challow", named after the Great Western station at which it was trialled during its development, again instigated by the GWR itself. Challow lamps are the holy grail for some collectors, as perhaps the GWR Heavy Duty Avometer should be...

[pmmunro]

ACWEECO were advertising the commercial version of the Heavy Duty Avometer by 1950 in this strange hybrid advertisement which uses a railway background to set the heavy duty theme, but using a Southern Railway Urie Class H15 heavy freight locomotive.

It would have seemed more appropriate either to use a Western Region scene or a much more modern locomotive than one built in 1924 when working for a company which had ceased to exist nearly three years earlier. Or did the ACWEECO advertising office just think that any railway image would do?

PMM

[The Philpott]

The terminals on the early Heavy Duty Avo look similar (possibly identical) to those used on the High Resistance Avo (Late '40's early '50's) and also those used on certain high voltage multipliers and resistance range extenders supplied as accessories.

They are captive type on my High Resistance Avo, and rather spindly. I took great care when straightening them as (at that point) i hadn't seen them on ANY other ACWEECO product.

Dave

[AndyGilham]

Good morning collectors!

Today I have received an DC Avometer Model 2, serial Number 6317

The instrument is in great condition and arrived safely from Canada. It was on Ebay and a bargain at £45, as I guess in Canada their are no collectors fighting over a rare instrument!

Its a later serial number and I noticed differences in the scale plate from others I have seen.

Andy

[Phil G4SPZ]

Nice find! You sound as happy as the cat that got the cream!

[pmmunro]

Andy,

It looks like your Model 2 has acquired screw terminals, either as well as or instead of the original fixed connections. Does it look like these might have been an "official" modification, or something done by the user?

It's interesting that this one found its way to Canada but I don't suppose we will ever know now if it was first sold there or was a personal export later.

PMM

[Superscope]

Ref Post #2698

That is an interesting Meter.
Not because it is a Model 2, as there are quite a few surviving examples
of Model 2's, but the Serial Number makes it one of the very last Model
2's manufactured.

I had previously estimated the last Model 2 to be around Number 6250, so
this particular meter pushes the estimate up by a margin.

6317 would have been very close to the end of Model 2 production, since the
Model 6 had started production by at least 6394, only 77 Units later.


It's a shame that it has been modified though.
Assuming it is modified, but this is something I have seen before on Model 2's.
I suspect this type of Modification was quite common back in the Day.



This brings me quite nicely onto some research I have been doing recently.


I suspect that, in addition to owners carrying out their own modifications
to Model 2 Test Leads, that Avo themselves offered the same Modification by
substituting the Case from a Model 6.

I am now aware of at least Two examples of Model 2's which reside inside
Model 6 Cases.

First impressions have been that Owners have swapped over cases to repair
broken Meters. Something that is still done today.

However, the Model 6 Cases on these Hybrid Meters have been professionally
changed with plugs blocking the /2 Button Hole and External Voltage adjust Hole.
Both of these Hybrids have the same identical Modifications, so clearly carried
out by the same Company, which almost certainly can only be Avo.

I will post the Photos of these Hybrids Meters after I've checked with the respective
owners.



Ian