AVO Multimeter survey

[Superscope]

As part of trying to update the information on Heavy Duty Avometers of
which currently there is very little, I have attached a few more Photos
of what I assume to be the Mk 1 that I posted about previously.

Note the lack of a Dataplate on the back.

A photo of what I assume is a Mk 2 has recently appeared on a different
Thread (Post # 13 ):

https://www.vintage-radio.net/forum/...d.php?t=193847


Does anybody on the Forum know the main differences between all the Marks?
And when they were released?
There were at least 6 Mk's.

From what I gather, the Mk 1 came out in 1948.
The Mk 2, looks like it was in production by around 1952.

The only confirmed Mk 6 had a 1984 Date.

I have no other information on the Heavy Duty, and most of the Survey
records don't have the Mk recorded either.

Service Data is sketchy, although a Schematic for the Mk 5 is in the back
of the Mk 5 user Manual which are fairly common.

I have an undated Schematic found on line which has some Value changes,
but no indication of which Mk it belongs too, so there were clearly changes
going on.

Does anybody have a known Mk 3, or 4?
How can you tell?




Ian

[Superscope]

Ref Post # 3020

Thanks for the Number Graham, although it doesn't seem
to fit into the number sequence we have.

Doesn't necessarily mean it's wrong though.

Where was the number located?
Normally, it's written in the lower Middle of the Scaleplate
and would normally have a Date Code as well.



Ian

[jez_145]

Originally Posted by Superscope

...
There were at least 6 Mk's.

From what I gather, the Mk 1 came out in 1948.
The Mk 2, looks like it was in production by around 1952.

The only confirmed Mk 6 had a 1984 Date.

I didn't realise the were six versions of the HD Ian. I always thought there were just five, of which the HD 5 seems to be the most prolific - by far.

My HD 5, Serial No. 14714, has 28.3.79 on it's Certificate of Test signed by H.J. Poole. I think I've added this info to the survey some time ago.

I'd certainly be interested to see a photo of a Mk6.

Jerry

[Superscope]

Hi Jerry,

Yes, I found your Serial Number entry.
You posted it in 2019.

We only have One Mk6 recorded.

Unfortunately, as is often the case, the Member only posted 8 posts
and never came back after 2005, so we can't ask any further details.
That was long before I got involved in the Survey.

I have no idea how the Mk6 was identified.

In the early days of the Survey, it was pretty much only Serial Numbers
that were asked for, so extra information was sadly lacking in most cases.

I'm planning the 5th Edition of the Survey report, but there is still a lot
of information I would like to get before it's published.
The Heavy Duty and Multiminor in particular.

Since the Heavy Duty has raised it's head recently, I thought I would put
the call out for any further information.


Ian

[jez_145]

Yes, it would be good to know more about the Heavy Duty. I think it misses out to the glory of the 7 and 8 models - which is a shame as it does have its good points. For one thing, the meter movement is much less damped than the other AVOs - which makes it very responsive. That's good for some measurements. It's not so good for higher resistance measurements though


Jerry

[The Philpott]

I haven't had any dealings with the heavy duty variant myself.

Referring back to Micheals Post No.3018, the s/no of my DC Avominor is 1034-93.

Dave

[Superscope]

Correction to my post # 3022.

The Multiminor does NOT have a Date Code as far as I'm aware.
I was still in Heavy Duty Mode when I was writting that.

The Serial Number, as far as I know for the Multiminor, is normally found
stamped in the lower middle of the Scaleplate, and it is often obscured
by the enamel paint covering, making it difficult to read or completely hidden.

I'm still hoping one Day, somebody will appear who bought a Multiminor
new, so knows the approximate Date related to their serial number.



Ian

[Superscope]

Thanks Dave,

I don't think we had your DC Avominor Number.


Is it a Stepped Side example?

Ian

[The Philpott]

Ian, 1034-93 is a smoothie. (What i would expect)
It doesn't have any lumps missing. (many of them do, presumably explaining the move to tougher step-sides..)

Dave

[Superscope]

Excellent, a Smoothie!

I shall be using that terminology going forward!



Ian

[pmmunro]

As well as the 5, possibly 6 main Marks there were two variants of some, if not all of them: a commercial and a railway signalling variant. The Railway signalling version does not have the variable sensitivity facility but a flat panel engraved (in all phenolic versions) with ownership details, usually "British Railways" and a region and/or department allocation.

Attached here is an advertisement from 1951 with a clear railway theme but the meter is a commercial one - not the Railway Signalling version. The locomotive is a Southern Railway Urie H15, dating from 1924 with what looks like an unbraked freight train! Hardly a model of the latest technology and perhaps done to emphasise that this meter was available to others than the GWR; but why in 1951? Who except British Railways would be buying multimeters for railway use in the UK, unless "The Electrician" had an overseas circulation sufficient to justify the advertisement.

A table of ranges is attached.

I have a marked-up circuit diagram for a GWR HD but it is not my own so I will not attach it here. If the originator would like to comment, he(she) could decide if it can be posted.

My GWR HD, Serial No.194-448 has acast aluminium front panel and back case, both painted black in wrinkle finish paint. The range marking are on an embossed brass plate.

Serial No.756-849 has a cast aluminium front panel and back case and the top labelling Variable Sensitivity/Normal/10mA DC = 100mV ans range plates are both surface mounted screen printed aluminium plates. Ther is no instruction plate on the back.The terminals, both black, are the high type as for the GWR meter. Possibly MK II?

Serial No. 3411-154 has a phenolic moulded front panel and a pressed aluminium case. both the sensitivity labelling and the range markings are moulded in. The terminals are the same type as a Mk I Model 8. Mk III?


All my other HDs are Mk Vs, with phenolic front panels and back cases. Terminals are the later red and black 4mm sockets/screw terminals. The back cases are mostly broken to some degree. It has to be wondered why a heavy duty meter should have such a fragile case.

I have information about plans for the development of a further version of the HD but whether this is the Mk 6 already reported and if it ever went into fullproduction, I don't know.

The HD Avometer in the 1952 catalogue seems to similar to the GWR version but with standard ranges.

PMM

[LincolnImp50]

Hi all,
I have recently discovered an Avometer 8 Mark 1......given to me by a neighbour.
It seems to have all of the original leads, leather carry case and working instructions booklet.

The serial number on the right hand side of the scale is 3246-C-252, so I'm assuming it is a February 1952 Mk 1 meter.

I have used the meter to measure the voltage of a household AA cell and it gives 1.5V on the 2.5V, 10V and 25V DC scales. I have not opened the battery compartment or tested any AC or resistance switch ranges.

If anyone wants any photos of the meter please PM me your email address.

Cheers, Brett

[ex 2 Base]

I may have registered my model 7 before, could register keeper please check. On the right side of the scale 23404 and also has the number No.7945. Could it have been manufactured Feb 1940 ? . At the moment a non runner, and I hope to do what ever during the winter months. Ted

[The Philpott]

More likely Model 7-September-1945. The 7 was inserted to befuddle us, as was the habit of reversing the position of the serial number and date code from time to time!

Dave

[Superscope]

Hi Ted,

Is the Number actually: 7945-23404 ?
i.e. with the 7945 first.

That number would make sence and fits in perfectly with the Data we have.
As Dave alluded too, that would make the Meter a September 1945 Vintage.

This Meter has not been recorded before.
We have one other Model 7 Mk II from you though from 2017.



Ian (The Register Keeper! )

[Superscope]

LincolnImp50,

Thanks for your Number, and yes, that would indicate a February 1952 Meter.
So Yes, a Mk I.

I would recommend getting the Battery Cover off and inspecting whether a
Battery has been left in or not.
Hopefully not!


Ian

[ex 2 Base]

Many thanks Dave and Ian for the info regarding my AVO 7. Yes Ian that is how it is on the dial 7945-23404, 7945 first. The battery box is clean pleased to say ,no signs of corrosion, no damage to the case either, in fact the front panel look almost like new,
but the correct terminals are missing. Rubber feet are there, needle not bent, but meter doesn't, a winter job. Ted

[Superscope]

Hi Ted,

What do you mean by "the correct Terminals are missing"
A meter of that age should have the Domed Bakelite Terminal Screws.


Do you have a photo?



Ian

[ex 2 Base]

Hello Ian, one of the terminals is the screw type with the Bakelite domed top broken away, showing the brass below, as it is, it would be safe to use. The other terminal is obviously a home made lash up. I'll be needing a couple of replacement when I've proven the movement is in GWO Pleased to say the threads are OK. Ted

[Pamphonica]

That collection of early Avos from the Richard Allan auction at Diss went for £500! Someone really wanted the models 3 and 6 in that batch.
https://auctions.twgaze.co.uk/catalo...ectr-lot-7134/