AVO Multimeter survey

[Henri ce2spr]

Here is another serial number for your survey: 108807-C-660. I own this meter already for a long time, when I still was sailing as a radio officer I purchased it back in 1981 or 1982 when our vessel was in drydock in Falmouth.
I used it a couple of years later when working ashore here in Chile as a service engineer in merchant marine ships, until I got hold of a new Fluke digital meter, after which the Avo-8 was put into storage.
It is still in good working condition and now deserves a place among all the other radio antiques like radio valves and the like.

Cheerio, with best regards from Viña del Mar in Chile.

Henri, CE2SPR.

[pmmunro]

Thanks for getting in touch Henri; I think your's is the first contribution from Chile.

Your Model 8 was 21 or 22 years old when you bought it but few of us would have considered that a problem then and would have expected it to be fully serviceable. Even now at 54 years old it will probably be perfectly good as I'm sure you will have treated it carefully. However, if it does need any attention these instruments are easy to work on - with care.

I sometimes like to project the age of items like Avometers as far back as their age now. In the case of your meter that would take us back to 1906. There can't have been many people using instruments from 1906 in 1960!

PMM

[Edwar65]

The Avo I have is the 8 mk3,
serial no - 108525-1169. I was also very lucky it seems on getting this with the VC1 voltage converter, I've heard these are very rare?
Picked this up from a chap in Hampshire for £12!
Hope this is of use to your survey,
Tom
Cardiff.

[mark pirate]

Just picked up another model 8 mkIII (panclimatic), mainly for the nice leather case, as it was only £2!
Serial No 107426.1169

Mark

[mole42uk]

I have an AvoMinor, serial U.81537-845. Can we date that?
I have the original user manual with it but not a lot else. I made a battery using one of the 4.5V cycle battery cells and it seems to work okay.

[Phil G4SPZ]

Hi Richard,

Your Universal Avominor would appear to date from August 1945 and its serial number is in the same numerical range as one in my collection from November of the same year.

I'd be interested to know which front panel details are present. If you look at this thread that I started a while back, and the attached thumbnails, you'll see that there are several styles - which one does yours look like, and what voltage ranges does it have?

Phil

[mole42uk]

Hi Phil,

Thanks for the date - that is interesting. I had looked at the serial number but couldn't remember which bit was the date code!

Mine has the 250V & 500V range sockets and looks just like your second image (November 1945). The front of mine is not in as good a condition, though - much of the white lettering infill has gone.

[pmmunro]

Richard,

The lettering is easy to restore and will greatly improve the appearance of you meter.

The official method, which I use, is to apply white cellulose paint (car touch up paint) over the characters - it doesn't matter if it goes over a little bit over the markings but avoid the "grain" of the panel. Leave the paint to dry for several hours then use a rag or a cotton bud moistened with methylated spirit to rub off the excess paint, again avoiding the grain.

PMM

[mole42uk]

Thanks, I'll try that. I want to clean the case first though, it's a bit grubby!

[mole42uk]

The lettering is now looking like new! I also did the few letters of my Model 7 that were missing the white paint. That looks a lot better as well, and I don't have to peer at the switches to see what the setting is!

[darren67]

Hi I have recently joined.
I have two Avometers that I acquired a couple of years ago. The first, which is frequently used, is an Avometer8 Mk V serial number 08167 8v/5/77, and working well. The second being a model 7 Mk2 serial number 63988-a-456. I picked this one up in a junkshop last year. At present it under reads and will need attention.

I read somewhere that date of manufacture is the serial number's last three numbers, so my model 7 mk2 would have been made in April 1956.
of course I might be wrong :P

Darren

[pmmunro]

Mole42,

It's good to know your meters are now looking better. Another slight improvement recommended in the service manuals is to "dress" the front panel with light machine oil ( 3 in 1). Having made sure the panel is clean, put a few drops, well distributed on the panel, and spread them with a soft piece of cloth. A cotton wool pad works well at the risk of shedding a few fibres.

Darren,

Thanks for your information. Your interpretation of your Model 7 serial number is correct.

Is your Model 7 reading low on all ranges and how much? Knowing this might help diagnose the trouble. If you need a circuit diagram or manual send me a private message.

PMM

[mole42uk]

Thanks, it's always good to get the outward appearance as good as the performance!

BTW, I have a PDF of the AVO service manual for a Model 8 - how much of that information is pertinent to the Model 7?

[pmmunro]

Mole42,

The general sections of the Model 8 service manual are a worthwhile guide to servicing procedure, as long as you realise that they were written nearly 60 years ago. At that time parts and assemblies were readily available from the factory and prices were reasonable so it made good sense to use the services on offer. Unfortunately that is not now a service we can use.

The manual recommends the use of substances which are no longer readily available, such as Chatterton's compound, which has been replaced by better substances to carbon tetra chloride, which apart from causing long term neurological damage, generated phosgene if inhaled through a cigarette, meaning that any worries about lung cancer were no longer a priority!

The official manuals also assumed some general knowledge of instrument repair work which makes using them a moderately demanding learning process.

In fact, AVO treated the Model 8 manual as the basic guide and issued shorter manuals for the Model 40 & 7 as supplements.

Contact me with an email address and I will send you Model 7 information to go with you copy of the Model 8 manual.

PMM

[micheal]

Another AVO for the survey, universal Avominor model2 2789-1154

[Station X]

Off topic post moved to a new thread here:-

https://www.vintage-radio.net/forum/...d.php?t=107252

[WaveyDipole]

I'm not sure whether data is still being collected for the survey, but I recently acquired an AVO 8 Mk3. The following appears on the front of the dial:

Model 8. No. 11681.365

The following also appears in pencil on the rear of the dial:

14.9.73c

9.8.74 CH * BA * EM (possibly EH?)

[Phil G4SPZ]

A Model 7 Mk II appeared for sale recently bearing the serial number 50648-A-1054. I hope it ends up in careful hands! However, the interesting point is that it had plain black Bakelite terminal knobs. In my humble opinion, the early Model 7 Mk II with its deeper profile switches and black terminals is the easiest to use and most elegant Avometer of all.

In my collection I also have a Model 7 Mk II with plain black terminals, serial number 62451-A-256, and two Model 8s with plain black terminals, dating from March and November 1955.

This has simply set me wondering when Avo abandoned the plain black Bakelite terminals in favour of the 'modern' plastic red/black dual purpose terminal posts? It must have been after 1956, long after the Model 7 Mk II was introduced. I bet PMM will know the answer!

[AdamAnt316]

Hello, everyone. I recently acquired an example of the AVOmeter 8 from an electronics surplus store (the only place I've seen AVOmeters for sale on this side of the pond), and have found it to be quite confounding. The meter scale and working instructions claim it to me a MkIV, but the case, handle and battery compartment are more similar to that of the MkV.

The serial number is handwritten on the meter scale (below the "8 IV"), and reads simply as "135." with no date code or other numbers afterwards. My theory is that it is some sort of prototype, or was factory-refitted with the new-style case, but I have no real idea. I have not looked inside the case as of yet, but will once I build up the courage to peel off the "UNIVERSAL" calibration stickers over the screwholes on the sides. I have attached some photos of this anomalous AVOmeter, and can supply more if needed.
-Adam

[pmmunro]

Adam,

The Model 8 Mark IV was a quite short-lived version which attempted to reduce production costs but was soon replaced by the Mark V.

One of the changes from the Mark III was the replacement of the phenolic resin (Bakelite) case by a thermoplastic moulding. At the time AVO, or their supplier, did not have a great deal of experience of large mouldings of this type and retained the case fixing screws of the earlier type. This created a weakness and many suffered severe cracks starting from the screw holes.

Eventually an official modification was offered which was a slightly modified Mark V moulding which did not crack nearly so easily despite having the fixing screws in the same place.

That would explain the style of case but the serial number is unusual. Mark IV serial numbers are usually printed on a self-adhesive label on the left-hand top edge centre of the case. It is probable that the repairer who fitted the replacement case found the label too difficult to change over and reverted to the older practice by writing all or part of the serial number on the edge of the scale plate. The serial numbers from the Mark IV onwards do not follow the earlier pattern so it is possible that the repairer was unsure exactly what to copy and chose the figures you see from amongst the full print on the original label, quite possibly 00135.

It was common practice for repairers to initial the scale plate in pencil on the back surface and sometimes to mark on the serial number, if this had not been done during original manufacture, which helped to keep the instrument with its own case, so you may learn more when you look inside.

If you are not familiar with Avometers, it is important that you know that the movement is quite open when the panel is removed from the case so a clean working environment is essential. When putting the meter back in its case it is advise able to apply a gentle downward pressure to keep the seal sufficiently compressed to ensure alignment of the screw holes, so avoiding undue stress on the holes.

PMM