AVO Multimeter survey

[russell_w_b]

Originally Posted by line sync

'...other than the 1.5v cell was square shaped.'

My 7 II has a flat paxolin sheet as wide as a square-section cell is diagonal, into which a 'D'-cell can be placed between copper contacts. This allows the 'D'-cell to sit in the gap where the square-section cell would fit.

With your 4.5V batteries, the -VE strips (long ones) both go uppermost.

[Waldeck]

Hi, my first post. I found your site looking for information on AVO repairs. I have one Model 7 MK2 ser# 68270-A-1056 that came from Canada (Toronto) and 2 units on the way; A Model 8 MK5 0032161 8V BC from Singapore and a Multiminor coming from Arizona.

I collect Panasonic Toughbooks and now it seems AVO's, the wife will be pleased. It would seem that there are many collectors out there from this very long/old thread.

I first used an AVO in the army in the 60's and sort of had an attachment to them, just like well made equipment. In the last few years started using one again and like the feel of it, in the field I use a small digital one.

[Phil G4SPZ]

Hi Waldeck, and welcome to the Forum. I have no doubt that your Avometers will be working long after your Toughbooks have given up the ghost...

As you have discovered, there is a huge amount of information on Avos here, and Forum member PMMunro is the acknowledged expert on Avo matters. Feel free to post any questions when you get round to testing your meters.

Phil

[Waldeck]

Thanks Phil, I shall do that, I have lots of questions on AVO's and other old test equipment that I have and am going to get in the near future. I got my first problem solved which was batteries, have to send them to my daughter in Devon and she will send them on to me. I'm sure there is a better way, but it gets me going for now.

If there is anyone in the US that repair/services AVO's it would be nice to know.

Bob.

[Sara-4711]

Gentlemen,

I have two AVO8 with no Mk...
Text on scale says; Model No8 170016-C-265 and 170339-C-265.
So the manufacturing date is clear.

The meter has a thermistor with shunt resistor (galvanometer) but
NOT the large copper coil on the resitance bar (Plate 1).
See attached IMG.

It seems not to be a MkII or MkIII or X...
What is it?
Custom made?
Does anybody know?
Appreicate any comments.
BR
/Lars G

[threeseven]

Do you have an image of the front panel ?

[Sara-4711]

Hello,
Thanks for your notice!
Please see attached image.
BR
/Lars G

[gezza123]

Looks the same model as my ( Universal model 8) until you open it up.
Hope this helps.
Gezza123

[threeseven]

Thats the tropicalised version.

[Sara-4711]

Originally Posted by gezza123

Looks the same model as my ( Universal model 8) until you open it up.
Hope this helps.
Gezza123

Hello Gezza,
Your AVO is for sure an AVO8 as can be seen from the rearside.....
But your instrument is lacking of the thermistor and resistor connected
to the galvanometer.

My AVO 8 has only 1A as max. DC current, which probably is the reason for not having the large copper coil shunt.
Discovered by member "threeseven". Thank you!
Min. DC current is 1mA
AC current runs from 100mA to max 2.5A.
I guess I have a custom made MkIII. Manufactoring year is 1965.
BR
/Lars G

[threeseven]

I'm wondering if it could be a special version for Post Office Telephones ? Normally they were marked PO and their model number but I suppose it could have been a trial version.

[Gulliver]

Originally Posted by pmmunro

Gulliver,

Could I confirm that it is the scaleplate and not the instruction plate that is damaged? It is unusual for Model 8 scaleplates to loose paint although it is a common failing on pre-1939 Avometers in which, in most meters, the scaleplate paint was applied over the nickel plating which provided the mirror arc.

Yes it's definitely the scale plate, the paint is flaking off but it's all still readable.

I don't know it's history, I bought it via the bay around 10 years ago and I do use it occasionally. I provide tech support for the Science department in a secondary school and it's actually the only meter we have that is capable of measuring voltage over 750V. When doing physics experiments with CRT's I use it to get the 2000V accurately from our HT supplies

[John_BS]

Avominor Mk1?

U129836-1054 Mod 1

Instruction manual scanned (it's falling apart). First four of eleven pages attached.

Slightly sticky movement. Very accurate calibration. Fast response meter.

The meter body looks like it just left the factory!

John

[Refugee]

Here we go this is a valve one
AVO Electronic Testmeter
Part number 12031 I.ET.I
No 1480-549

There is a restoration coming on here

[Paul Adams]

AvoMinor type 'E' S/N: E.5187.1942.

Paul.

[pmmunro]

Sara4711,

The meter whose front panel you have photographed is definitely a Model 8 based special, and one I have not seen before.

Yours has more direct current ranges than normal, but not the 10A range.

Could you scan or photograph the instruction plate on the back please?

Sorry to have taken so long to respond to your original post.

You give two serial numbers - do you have two of the same version?

PMM

[pmmunro]

John,

This looks like an Electronic Testmeter Mk II, the version with the 6SN7 twin triode. Do you need a manual? It can be downloaded from more than one internet site or please get in touch if you do need one.

The earliest version has the meter at the bottom of the panel and the switches at the top and uses two EF50s connected as triodes. If anyone has a circuit diagram or manual for one of these, I be very interested in a copy.

The later Mk IV can be distinguished by its hammer finish paint in contrast to the wrinkle finish of the earlier ones.

Unfortunately there is a belief that the movements of these meters are good for replacing Valve Characteristic Meter movements which I'm not convinced is practicable but it seems to inflate prices and probably results in quite a few scrap Electronic Testmeters.

Whatever the cause and effect I'm still looking for an affordable Mk IV.

PMM

[Refugee]

Tonight I opened the case and it does have the 6SN7. I powered it up on the Variac and it is 110V only

I was able to establish that the movement is good and found a very dodgy waxie that has made a mess. It measured the output of a diode tester and indicated two volts.

I have downloaded a circuit diagram and have a feeling that the crackle finish paint is going to be the hardest bit to sort out.

[Radio Tech]

Hello SPC, you wanted some info to help you compile articles on the famous AVO, mine is the Avometer 8 mk 5 and its serial number is 69390 8V/4/75 and I got this from a retired service engineer.

Hope this helps.
Ken

[Andrew Sinclair]

Refuge, I am trying to master crackle paint. It can be bought in aerosol form in black or red. If you need grey (as I do!) then you can spray a couple of coats of black crackle paint with a 15 minute delay between coats. Leave for a day and then warm the panel to about 30C and spray a top coat of the appropriate colour. It will wrinkle nicely. (Most of the time!)
I bought my wrinle paint from Halfords (I have no connection apart from a satisfied customer.)
Hope this helps
Andrew