AVO Multimeter survey

[pmmunro]

Ken,

Thanks for the information which is always welcome. I hope you will find the forum interesting and useful.

Sadly SPCH died in February 2011 (see SPCH - In Memoriam) and since then I have been doing my best to support this survey.

PMM

[Refugee]

I have started a new thread for the AVO Electronic Testmeter in the test gear section.
The restoration is on and even my avatar has changed to the one with power on and the fan spinning to support this.

[Refugee]

Originally Posted by Andrew Sinclair

Refuge, I am trying to master crackle paint.
Andrew

I am going to start a new thread in the cabinet restoration section for this.

[Paul Adams]

Another one saved from the skip, actually found in one and not working due to the ‘+ terminal’ badly corroded and giving no reading on any ohms ranges also odd readings on the volts ranges, anyway giving the offending terminal a good cleanup with a ‘Fibreglass pen’ readings were restored.

A good scrub with a toothbrush and soap, re-applied the lettering and a good polish with ‘Bumper restorer’ and it’s like new again

Before and after photo’s.

Model 8. No.2290-C452

Paul.

[rswanborough]

I have an AVO Multiminor MK 4 with the number 82474 on the case.

[chuckey]

AVO 75565 8V/6/75 here. Someone connected me to 230V AC while switched to 10A AC. The inside of my case was sputtered in copper from the switch, still my current owner has replaced both the moving and fixed switch contacts and I work again!

Frank

[Camino1]

An AVO 8 MK V. Serial 75223 8V/6/75. Nice but without leather case or original leads. Still within specs. A friend borrowed my other Avo. Will report on that one later.

Henk

[Camino1]

The other one has just been returned. It is an AVO Mk V 44671 8V/10/74.
Works ok accurate on voltage ranges did not check the others.
Battery and fuse clips with slight corrosion. A crack in both red terminal clips.
Black cap on cutout missing. There is no serial number inside the battery cabinet. It is on the cabinet lower left hand side. The white lettering has a brownish color. Coffee? Sigarets?

Perhaps my other meter met Chuckey's in the factory. The serial numbers are not far apart.

Henk

[Cold Cathode]

I have had 2 AVO's in my possession since early 1970's
AVO 9 mk 11 No 13075 468 (Dover address)
AVO 8 mk 11 No 9308 C 364 D (Vauxhall Bridge address)

Hope this helps your survey

I still use them to measure current as DMMs always seem to blow expensive fuses which are a pain to replace.

[pmmunro]

Cold Cathode,

Thanks for the information on your meters.

It may be that the 'D' suffix to the serial number of your Model 8 indicates that it was one of the first to be made in the Dover factory which opened around March/April 1964.

It is one of the last of the Mark II Model 8s as the Mark II was announced in June 1964.

PMM

[Paul Adams]

Just acquired an avo 9 mk4 with a few problems, I think they are mainly switch related, as the meter is intermittent on all ranges.

Serial: 38700 94/4/71.

I have a circuit for a model 8 mk4, is this the same as the 9 mk4?

Paul.

[Paul Adams]

Regarding the Avo 9 mk4, so far I have found various problems, one that is the shunt chain is o/c in R10; 0.45ohms (see photo)

Anyone have any idea’s as to how I can obtain the required value?
The nearest I can get is 0.47ohms.

Oh and I have re-scanned the circuit from the manual, as the other wasn’t too clear.

Paul.

[Phil G4SPZ]

Hi Paul,

If you put an 10 ohm resistor in parallel with your 0.47 ohms, the resultant combination will be 0.4489 ohms, as near to the required 0.45 as makes no difference. If you can find an 11 ohm resistor, this will give you 0.4507 ohms, pretty well bang on.

I've actually got some 11 ohm 5% resistors if you'd like one. These are only 0.25 watt rated but in this application I think that would be sufficient - which current range uses the 0.45 ohm shunt?

I'm sure you said - in writing on this public forum - that you were going to stop collecting more Avometers... this affliction definitely appears to be incurable in the worst affected sufferers like yourself

[Paul Adams]

Hi Phil,
Sent you a P.M; Regarding the resistor, as for the affliction, I think I need professional help!
And there’s more on the way.

Paul.

[Paul Adams]

Latest acquisition is a avo8 mk3 with the serial: 25377.965.

This arrived in a sorry looking state, with paint on the front leatherette finish of the Bakelite (mottled finish) of the meter, and my normal approach of removing it with a small needle didn’t work, I ended up by carefully going over the paint with a small wire brush, which to my amazement removed it all and no harm to the finish.

The knobs on the switches were scratched, and the scratches removed with brasso, so were the escutcheons which were given the same treatment with the polishing, the old lettering removed with a fine needle, a good clean with a toothbrush, and finally new lettering applied.

A good buff up with some car bumper restorer, and it’s looking like new again.

I keep saying no more, but…..

Paul.

[Phil G4SPZ]

Paul,

Well done. I too am always impressed by the resilience of the Bakelite front panels of Avometers, up to the Model 8 Mk IV at least.

I've sent you a PM. Cheers,

Phil

[Electronno]

I recently bought an Universal AVO Minor, which seems to be quite old.
It has a 2.5 mA movement.
See http://www.glowbug.nl/instrument/Meters.html

As a contribution to your survey:
it has serial U 86310.146 hand written/painted on the scale

Is there any key to date these serial numbers?

Regards,
Onno

[Paul Adams]

Hello Onno and welcome to the forum,

From what I can gather the last three digits are the Month and the Year, so yours would be January 1946.

I’m sure that someone will correct me if I am wrong.

Paul.

[pmmunro]

Welcome to the forum Electronno.

Paul's interpretation of your serial number is correct. The Universal Minor was introduced in June 1934 and continued in production until around 1954 by which time there were two slightly different variants. These were replaced by the Avo Multiminor which had a single rotary switch to select the ranges and functions.

The Universal Avominor was used by the British armed forces during the Second world War and afterwards. There was also a modified version used by the Air Ministry to their Type 'E' specification. Although the 'E' used the same basic case moulding which still had the word 'Universal' as part of the moulding it was a DC only meter, but it had a fuse to protect the movement.

It depends who you ask on what counts as an 'old' meter. Probably for most of us an Avometer is officially old when its about 20 years more than we are. That means for the very oldest among us you'd have to go back to the original of 1923 for an Avometer to be really old. An Avometer which has been carefully looked after will usually still be good after well over 50 years use so it still isn't old in the sense that it no longer useful.

PMM.

[Electronno]

Thanks for the information and the philisophical digression. Though the meter is older than me, it doesn't meet your standard for my "old" meter.

From the circuit diagram found elsewhere here, I learned that the movement is more sensitive than 2.5 mA. It is the chain of shunts that makes it less sensitive?

Thanks to all who contributed to the body of information in this thread.

Regards,
Onno