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Old 18th Apr 2013, 11:07 pm   #1
Phil G4SPZ
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Default Universal Avominor intrigue and mystery

I wonder if anyone can help or advise on the various models of Universal Avominor that were produced? The various Avo catalogues that I have seen list two types, the "Model 1" having a 2.5mA movement and a sensitivity of 400 ohms-per-volt, and the "Model 2" with a 250uA movement and 4,000 OPV sensitivity. So far, so good, although I've not come across a Model 2 yet.

The Air Ministry "Model E" is a quite common variant of the Model 1, with the 2.5mA movement and distinguishable by the fuse in the bottom left hand corner. However, I have found at least three other variants of the "Model 1", all with 2.5mA movements but different panel designs and different voltage ranges. They all have the same 20,000 ohms resistance and 2.5mA, 5mA, 25mA, 100mA and 500mA current ranges. However, instead of the 250V and 500V ranges, two variants have 500V and 1,500V ranges. The variants are shown in the thumbnails as follows:

1. "Standard" Model 1 as in catalogue, with 5, 25, 100, 250 and 500 volt ranges.
2. Early variant with 5, 25, 100, 500 and 1,500 volt ranges and raised lettering to range switch.
3. Later variant with 5, 25, 100, 500 and 1,500 volt ranges and engraved lettering to range switch.
4. All four, including a Model E (top right).

The change from raised lettering to all-engraved lettering must have occurred between the 1939 and 1952 catalogues, at a guess around 1948.

I have not seen the 500V and 1,500V range variants in any Avo literature. If anyone can shed any light, I'll be grateful!

Phil
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Old 19th Apr 2013, 7:23 am   #2
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Default Re: Universal Avominor intrigue and mystery

Quote:
Originally Posted by Phil G4SPZ View Post
I wonder if anyone can help or advise on the various models of Universal Avominor that were produced?

The change from raised lettering to all-engraved lettering must have occurred between the 1939 and 1952 catalogues, at a guess around 1948.

Phil
A technique is applied in respect of bakelite moulding whereby economy is achieved, when only small changes are required between several models of an item involving a single basic structure. The dies are made incorporating removable inserts which are changed as needed. Careful examination discloses where this technique has been used.

As a result another interesting factor is provided when collecting Avos. It becomes apparent that as time has passed Avo became aware of this technique and used it extensively.

There has been criticism that Avometers were rather crude in some respects, having been very much hand made. However this enabled meters to be custom made as required and must have added a second layer of customers. Certainly no other brand features so many models and variations of those base models. Another reason why Avos have proven collectable as opposed other brands.

Trevor.
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Old 19th Apr 2013, 7:51 am   #3
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Default Re: Universal Avominor intrigue and mystery

Hi Trevor, good to hear from you again. I'm sure I was technically incorrect when I mentioned "engraving", and perhaps "indented moulding" would be a better way of describing the very smooth legends that are filled with paint or wax.

I'll try to post some close-up images shortly showing not only the legends, but other differences between the early and late panel designs of the Universal Avominor.
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Old 20th Apr 2013, 1:19 am   #4
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Default Re: Universal Avominor intrigue and mystery

Fair enough Phill.

I have also noticed where blank inserts have provided a panel where hand/machine engraving can be applied, I would presume where a very short run of custom made items are involved. Again this illustrates the flexibility of the Avo set up, as well as a confirming a willingness to cater for a customers exact requirements. All of this must have had a significant bearing on the well demonstrated lengthy allegiance to the brand AVO.

Trevor.
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Old 24th Apr 2013, 9:49 pm   #5
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Default Re: Universal Avominor intrigue and mystery

I have reported two more Universal Avominor serial numbers for the survey, and at the same time pinned down the date of the change from "raised" to "indented" legends on the range switch with a little more accuracy.

Serial number U68536-744 (July 1944) has raised lettering.
Serial number U85135-1145 (November 1945) has indented lettering.

So the design (and the moulds) must have changed sometime between July 1944 and November 1945, and my earlier guess of 1948 was way out. If anyone has an instrument within this date range, perhaps they could advise the style of the switch legends?

I've also established that there are two distinct styles of indented legends on the range sockets on these meters. The earlier style (up to at least 1945) has a smaller typeface and no dot between the letters M and A, e.g "500 MA". The later style (1950s era) has bigger letters and "500 M.A."

I now own, or have seen, six of these instruments and no two are the same!
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Old 25th Apr 2013, 11:13 am   #6
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Default Re: Universal Avominor intrigue and mystery

Phil:

Certainly this 1954 example has the rather clumsy punctuation!

John
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Old 25th Apr 2013, 3:23 pm   #7
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Default Re: Universal Avominor intrigue and mystery

Thanks for the picture, John. This seems to be the most common post-war style, with the maximum 500 V range and the unnecessary punctuation. At least "M.A." is better than the typical and even clumsier wartime "M/A".
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Old 25th Apr 2013, 3:37 pm   #8
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Default Re: Universal Avominor intrigue and mystery

It must pre-date the decision to use m for milli, M for mega. Back in the days of 'Meg'

Raised lettering on a product is easy and cheap because it's engraved into the moulds. Indented lettering is hard because it needs raised lettering in the mould by engraving everything around it away. Having changeable mould parts to change legends is smart. Often text is the most fragile part and can be replaced when worn without building an entire tool again.

David
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Old 9th Jun 2013, 3:37 pm   #9
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Default Re: Universal Avominor intrigue and mystery

Oh, it gets worse... I've found yet another case style for the Universal Avominor. My latest acquisition has the early type case, but there are no raised circular rings surrounding the sockets.

The serial number is U23115-36 and whilst it's tempting to think this may be a 1936 instrument, its condition suggests otherwise!

Phil
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Old 10th Jun 2013, 2:00 pm   #10
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Default Re: Universal Avominor intrigue and mystery

I have one of these but unfortunately it's a little beat up,but still works.
The glass is broken and the lettering on the various sockets are not whitened,plain same colour as the avo,someone stuck a piece of Perspex over the meter movement,the rear is banged up and the instructions printed on the rear half are unreadable.inside is one 1.5 AA Duracell battery.wouldnt mind restoring her.
Where on earth would I get the glass from to start with.
Regards Roger.
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Old 10th Jun 2013, 2:16 pm   #11
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Default Re: Universal Avominor intrigue and mystery

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Where on earth would I get the glass from to start with.
Try a picture framer.
 
Old 10th Jun 2013, 3:44 pm   #12
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Default Re: Universal Avominor intrigue and mystery

If you can make a template most glass cutting companies will do it for a couple of pounds. Ive had several made up for my collection of AVO's.
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Old 11th Jun 2013, 10:42 am   #13
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Default Re: Universal Avominor intrigue and mystery

glass for Avo. As jamesvalves says, make up a card template. Then go to your local glass merchant. A picture framer may be less versatile. But make sure you get thin 2mm glass. For windows they are required to use 4 mm. Pictures also are usually thicker, some other regulation. So ask for horticultural glass, or explain what it is for. Otherwise Health and Safety regulations will restrict the thickness of glass supplied.
My local glass merchant found is quite interesting to cut on a curve and then take a notch out for the zero adjuster spike. wme_bill
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Old 13th Jun 2013, 3:22 pm   #14
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Default Re: Universal Avominor intrigue and mystery

Okay, back to Universal Avominor case styles. I think I can now conclude that there were at least six different case styles and range variants between 1935 and 1954. I'm posting the following images in two groups, the first three being the older style with raised range-switch lettering, dating from 1936, 1941 and 1943 respectively. The second three are the later style with indented range-switch lettering, dating from August 1945, November 1945 and 1954. The instruments with the as-yet undocumented 1,500 volt range are from June 1941 and August 1945.

Peter Munro has kindly confirmed the age of the 1936 instrument, and Paul Adams has an identical model in his collection with a 1935 serial number, so this style would appear to represent the earliest production.

If anyone owns an Avominor which differs from these, particularly a Type 2 (4,000 OPV) then please post an image and serial number!

Phil
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Old 13th Jun 2013, 3:24 pm   #15
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Default Re: Universal Avominor intrigue and mystery

Here are the second (post-war) batch.
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Old 13th Jun 2013, 4:51 pm   #16
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Default Re: Universal Avominor intrigue and mystery

Well Phil mine looks like the 2nd one in the first set of pictures.
Circa 1941 you say.
They don't make em like they use to ,do they !
Regards Roger.
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Old 13th Jun 2013, 6:05 pm   #17
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Default Re: Universal Avominor intrigue and mystery

You're right, Roger, they don't. My oldest Avo is a DC Avominor dated February 1934, and it still works accurately.

The last digits of the serial number, following the dot or dash, indicates the date of manufacture in the format (M)MYY, so 941 = September 1941. Pre-war models have a single Y digit representing the last digit of the 1930s decade, hence my 1936 model has "36" meaning March, 1936.
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Old 13th Jun 2013, 9:26 pm   #18
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Default Re: Universal Avominor intrigue and mystery

Where's the serial no located on these Phil ?
I know the Avo 8 is on the meter face.
Truly a portable multimeter and still accurate to this day,do you make the test leads or are they readily available ?
The very best regards Roger.
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Old 13th Jun 2013, 10:08 pm   #19
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Default Re: Universal Avominor intrigue and mystery

Hi Roger,

All the Avominors I've seen have the serial number on the scale plate, as below. Occasionally you find one where the serial number has been erased, possibly by the person who originally liberated it from its rightful owner...

I have acquired a handful of original test leads, which are double cotton covered cables with standard "wander plugs" on the meter end and elegant shrouded male sockets on the other, into which small crocodile clips or probes can be plugged. For use nowadays on serious voltages, a modern set of test leads can be used if fitted with wander plugs to fit the Avominor's sockets.

Good contact is important, and I use a pipe cleaner and a spot of Bake-O-Bryte to clean any tarnish off the inside of the socket tubes.

Phil
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Old 27th Sep 2013, 4:47 pm   #20
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Default Re: Universal Avominor intrigue and mystery

Recently acquired is this ’Air Ministry’ type ’E’, with all of the type ’E’s that I have, this is a variant that I haven’t seen before, awaiting Phil’s comments.

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Serial number in the appropriate section.

Paul.
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