AVO Multimeter survey

[SPCh]

Thanks to everbody for the steady stream of information.

Zulu95, your Universal Minor (UM-1) dates from July 1942 (I have number 48547 in my collection from the same month). 120,000 were built in the 14 years from 1938 (plus some military variants). The UM-1A (basically the same spec. but with a clever "low ohms" range added) was introduced around the end of 1955 !

The survey is a slow process, and heavily skewed towards the Model 8 Mark II which seems to be the one most "restorers" have. Around 120,000 of these were built in the ten years from 1956 at a fairly steady rate. That compares with around 40,000 Mk Is (in the five years from 1951), and some 90,000 Mk IIIs (in the five years from 1964).

It's good to see so many of you taking an interest. AVO (whose head office is now "across the pond" in Ohio) has no interest in the history of its product range at all, and is only interested in badging oriental flimsies. It's humbling to consider that the first AVO meters are just coming up to 83 years of age, with some still working, still accurate, and at least one with its original calibration seal intact. Where will the flimsies be even 20 years from now, I wonder ?

Keep the Serial Numbers coming in, and any questions or comments (in an appropriate other thread or by PM).

[Zulu95]

After reading the posts here I guessed it was a 1942 model. Good to know.

[jasee]

I have quite a few:
A minor U.15/6076.245, A Universal Model 8 9xxxx-C-559, A Model 8 Mk 7 5xxx-442, and two Model 8 Mk 5's 0xxxx 8V/11/77 and 5xxxx 8V/3/75, HTH

[wireful3]

I have just noticed this thread on AVO meters and have an AVO 7 No 9xxx2-A-185. There is little information on it but it is in a Hammer finish gray metal case. I don't know whether this is common as all I have seen before were black. I can't set it up on resistance range to give no change on switching between the ranges, this might just be the batteries. Can anyone comment?
I also have an old small Avo in a bakelite case stored away somewhere. It is not the common Avo minor as it has switched range selection and has the meter and selector switch side by side. When I find where I stored it I will let you have serial number and more details.

Regards John

[SPCh]

Thanks John.

Could you please confirm the last three digits: is it really 185 or could it be 158 ?

The zero setting problem is usually batteries, or dirty connections thereto. Could be internal but isn't normally. A new 1.5 volt battery and perhaps a tickle with the emery cloth should fix the problem for the 10kohm and 100kohm ranges.

Your "little one" sounds like a Multiminor. Range selector knob on the left with ohms zeroing knob immediately above. Nice little workhorse.

[brunel]

Avo 8 Mk.6

1349 M 92225

Mod 8v1 1/88

Regards

Brunel

[wireful3]

Originally Posted by SPCh

Could you please confirm the last three digits: is it really 185 or could it be 158 ?
The zero setting problem is usually batteries, or dirty connections thereto. Could be internal but isn't normally. A new 1.5 volt battery and perhaps a tickle with the emery cloth should fix the problem for the 10kohm and 100kohm ranges.
Your "little one" sounds like a Multiminor. Range selector knob on the left with ohms zeroing knob immediately above. Nice little workhorse.

I was Completely wrong on the serial No. as I tried to read it in poor light. It is in fact 165.

Your description of the Multiminor is spot on. I will have to seek it out again. From memory I agree with your comment and I think the ranges more useful for battery work than the 7.

Thanks for the tip regarding setting must change the D cell and have another go.


Regards

[SPCh]

Thanks, John

-165 puts it exactly where it should be.

That's the whole point of the survey, patterns are emerging (at least for the Model 7s and 8s) which allow me to question/challenge what appears incorrect. Not a lot does.

But as a reward for everybody who's contributed and shown an interest, I have one unexplained "oddity" which I can share with you.

A Model 8 Mark II (and it really is) with a serial number which puts it very definitely at end 1957 / beginning 1958, but with a date code which insists it's from May 1967.

By that date it couldn't have been a Mark II, but would have to have been a Mark III - with a substantially lower serial number in a significantly different format. So; just a slip of the pen ? Certainly not an instinctive one (digit-reversal or wrong-digit-duplication). Was it just that one meter, or the whole day's production (40 ish) or the whole month's (1000) ? Clearly the perpetrator had something else on his or her mind. To put it into context, the late 1950s were still the "Dixon of Dock Green" era; "Z-Cars" were still some years away.

Keep 'em coming guys, and gals; I'll keep you informed.

[jim_jobe]

Hi,
I have a Model 8 Mk V, serial number: 96470 8V/9/73.

Vive le liberation!!

Jim

[TNC]

Hi SPCh

Mine (in common with many others I assume) is ex BBC - covered in their sticky labels!! It's a Model 8, MkIII - serial no: 103489. 969.
I assume that means manufactured in Sept. 1969?

Other interesting BBC info:
"OUPC Ref. N380";
"Class: Test" and
"Loc. T005".

It came with the AVO leather case in excellent condition - and even that carries a serial number(!): 6320 - 052.
Does that mean anything to anyone?

Regards,
Trevor.

[Zulu95]

I just had an Avo 8 delivered I won on eBay. I had forgotten just how honking big these things are! Came with probes, carry case with shoulder strap. Canadian Supplier Plate on the battery door.
Details.
Model 8 Serial No. 6352 C1052

I guess it was born in October 1952. If so I'm a month older!

[pmmunro]

Trevor,

I don't know if you have a BBC background, but one of my memories of their induction course was the presentor assuring us that absolutely everything had the corporate name on it, including the paper with the perforations between sheets. As this was before computer print-outs were common, there was little doubt that it was the shiny sanitized kind.

The number on your case is a catalogue number, not a serial number. I'd have to check, but you could probably order a replacement from Avo using that part number if you were so inclinded and willing to part with a little over £100, plus tax.

PMM

[Zulu95]

Just added a 40 to my collection. Needs some work internally. Made in 3/43.

[Mike Fulton]

I have two AVOs to hand and another two in the loft.....
Those to hand are:

Model 7 S/no: 40644-a-353 VGC
Model 40 S/no: 18874-847 Mint with full set of shunts - Cased & unused

Those in loft are a model 7 - minus AC Tx (anyone want any spares??) and model 8 in fully working order & recently calibrated but needs back case (bakelite if anyone wants to send me one) details to follow.....

[Dave Moll]

I have recently acquired the following (in a local auction, so no concerns about serial numbers being traceable - if the seller has, that's his (probably not hers) problem):

model 8 mk II serial no. 130092-C-1161 (on scale)

model 8 mk V serial no. 036882 DC 8V (in battery compartment)

[timewave]

Hello SPCh

I have a model 8 Mk IV S/No 02699 524/170. My father bought it for me back in about 1967/68 maybe. It was brand new and I think it cost about £30.It has seen a lot of use and is now in need of some TLC.
Also have 2 model 8Mk V the S/Nos are very worn 1XXXX 8v/6/74 and 0XXXX and the rest is a mystery.

Red terminal cover,ohms zero knob and top of Rev M.C. switch missing on one of the Mk Vs and all 3 are battle scarred but wouldn't part with them.

Cheers

John

[Rob Lines]

SPCH
I have 2 AVOs to include in your survey.
The first is a Multiminor Mk V, whose only sign of a ser no is on the Cal Label (marked Brush Elec Machines Ltd & dated 16 Feb 78) shown as Inst No 60786. The front pael of the Avo is engraved BEM Maint no 1.

My Model 8 Mk 2 is Ser 162493-C-763. There is a sticky label on the side proclaiming 'Serviced by London Instrument Repair Centre', no date, but the label has a Thorn logo on it. This avo was bought for a few pounds at the NVCF a few years ago, it had multiple faults which I managed to repair but the most interesting was one of the finw ww resistors (1230 ohm) which, being o/c I painstakingly unwound until I found the break. At the break I found the 2 ends of the res wire laid carefully alongside each other in the wax, this resistor could never have worked from new! I carefully soldered the 2 ends together and rewound the rest back on and bingo, one very nice avo again!

I will dig out from my attic my 3rd Avo when my back allows climbing and post details for you

rgds
Rob

[SPCh]

Interesting. The open circuit 1230 ohm resistor would have given a small error on the OHMS X 1 range - probably not enough to upset a user, or to fail the production test.

[George Epple]

Hello... my very recently acquired AVO meter is a model 8 MK IV serial number 74133 (84/8/72). Functions quite well and in almost new condition except for the "Ohms divided by 100" scale not quite zero-ing. Possibly caused by a dirty pot?

Regards,
George

[Sam]

Originally Posted by George Epple

Functions quite well and in almost new condition except for the "Ohms divided by 100" scale not quite zero-ing. Possibly caused by a dirty pot?

Have you changed the batteries? Old batteries cause problems zero-ing the meter on the resistance ranges. I think it is the 1.5V D-cell for the Ohms/100 range on the 8, and not the 15V battery.

Sam