AVO Multimeter survey

[The Philpott]

Richard, when you have a delve could you advise the average resistance of the fuses? Would be useful to check it against my Model 4- i can't recall whether it was intact on purchase or i just fitted a resistor. Thanks!

Dave

[Superscope]

Hi Richard,

Probably not worth asking, but just in case, can you confirm that
it has the Bakelite Control Knob covers, and when you do open it,
that it has the Movement Magnet perpendicular to the Scaleplate
like found in the Model 7's and 40's.

Should be, as that is quite a late Model 5, but it's always worth testing
the Avo theories when the option is available.

Is the case original ?
Not actually sure how you would tell though, I have never seen a Model 5
with a Case!
How about the Leads ?


Dave,

All the Fuses I have measured that were in tact when I got them
have all been around 4 Ohms as per the ACWEECO Schematics.
I say around, because they have generally been about 4.2 or 4.3 Ohms,
but then my Equipment isn't calibrated, but I think that is fairly accurate.
Is it Drift, or was that how they were made?
We will probably never know.

On the Fuse I restored a Year or so back for a Model 5, I found 4.6 Ohms
was a better match for the Meters accuracy, but then after 70 odd Years
anything could have drifted some what.

I think it's worth calibrating the Fuse to the Meter these Days, as it isn't
like you are going to be buying new ones anytime soon.



Ian

[Barnmead]

Thanks for the comments and suggestions. No further ahead yet but here are two pictures

[Superscope]

That's a nice find Richard,

Looks like you have Two spare Fuses as well.
What a result!

Are they working Fuses ?


Ian

[Barnmead]

Sadly both fuses are duff.

I have now with difficulty prised it apart and can confirm the magnet is perpendicular to the front panel. Black metal casing, Wooden battery box, serial number also scratched on back of scale plate.

[The Philpott]

- Note the colossal winding for the high voltage range. Found to be intact on my Mod 4, much to my surprise.
Dave

[Superscope]

The Model 5 is a really nice Avo Meter in my humble opinion and as
has been mentioned previously, the Low Resistance Range
is quite accurate (significantly better than 5% in my experience)
and useful.


Richard's Meter confirms again, that the later Meters have the
Perpendicular Movement Magnet, Bakelite Control Knobs, and the
Battery Bay Spikes are on the backs of the P and R controls rather
than having their own Mountings on the back of the Front Panel.



Ian

[Barnmead]

I have read with interest the helpful thread back in December 2018 "Avo 36 range restoration" particularly about the fuses as all mine are dead and bridged with fine wire.

Answers to your questions:

The leather case was is almost identical to other genuine AVO ones I have except it has green felt like lining and steel rather than brass buckles and studs for the shoulder strap.

The leads were cloth covered and ended in a screwed (1BA?) piece of brass rod into which the probes or croc clips fit, Hook spades on meter ends. I have made new leads.

The Z adjuster on mine is chrome plated.

The case appears original and lists 36 ranges. Unlike later meters the anti-tamper screw is on the lower left hand side.

I discovered an open circuit on one of the high value resistors and burnt out end turns on the R ohms adjuster, both now fixed. Fortunately with a magnifying glass I found the broken ends and after many attempts managed solder a piece of copper wire to join them up.

I used an inch or so of wire from a 400 ohm resistance bobbin wrapped around one of the fuses to get about 4 ohms and found the meter was remarkably accurate, not bad for something made when I was a toddler!

[Pamphonica]

Could someone please add a link to the post with the latest survey, maybe also adding it to post #1 at the top of this huge thread?
Mods?
(I can't find the Survey 4th Edition)
many thanks
-Jeremy

[Pamphonica]

Three Model 8s spotted on an Ebay advert:
(not showing on the 3rd Edition Survey)

8 Mk I s/n 4455-C-452 (Apr 1952)
8 Mk II s/n 69621-C-158 (Jan 1958)
8 Mk III s/n 102742-969 (Sep 1969)

-Jeremy

[Superscope]

I have only just noticed that the Avo Test Bridge, has not been previously
recorded in the Survey Database.

Ok, it's not an "AvoMeter", but it is an Avo and it is a Meter and more importantly,
it's analogue with a Moving Coil Meter so ticks all the Survey Boxes.

I think it would be nice to record this Instrument going forward and I know a fair few
of these still survive and several Forum Members have them.

So if anybody has one, and would like to dig the Serial Numbers out, I will update the Survey accordingly.

Also, if anybody knows any more information about them, that would be useful.

I know a Circuit Diagram is available, and one of our Forum Members
produced a nice Restoration Manual quite a while back.


Ian

[AndyGilham]

Ian,
My Test Bridge is serial number 53061046, which I think is October 1946

Andy

[Superscope]

Thanks Andy,


Well, that's two of them in the Survey now then!

Is that Serial really in one continuous Number ?



The Photo I posted earlier was a September 1944 model
Serial Number 4030-944

Which would indicate that not a lot in the grand scheme of things
were being made.
1500 in Two Years is not so many.



Ian

[hilitevr]

My AVO Test Bridge serial number 4181-1144

[Phil G4SPZ]

Mine is 2693-1243 and carries additional markings as shown.

Phil

[Superscope]

Thanks to Andy, Trevor and Phil,



That's Five Test Bridge Serial Numbers in the Database in less than 24 Hours.
I pulled one from the Restoration Manual itself.
Great result!



Based on this limited amount of Data, I would estimate that this Bridge was
released probably somewhere around 1940 at the earliest.

Although I have seen references stating 1939, the figures don't currently
support a launch Date quite that early, but we still need more Serial Number
Data to improve any conclusions we can gather.


Phil

Is the Overlay fitted to your Test Bridge a Homebrew item made by STC
or, is it an Avo item do you think ?

Obviously a similar idea to the Power factor overlay found on the Model 7




Ian

[Phil G4SPZ]

Hi Ian,

At a guess, it was made by STC, but equally it could have been from a batch made by Avo for STC to their specification. The front panel STC legend is very neatly engraved, or more likely moulded-in. I have a model 7 with a Marconi legend similarly engraved.

Phil

[TowerRadio]

Serial number of my bridge is 7311-648 Les.

[Phil G4SPZ]

This thread has prompted me to dust off my ATB and try it out. Seems to work on all ranges, although the calibration is a bit out as would be expected.

The Restoration Manual actually quotes the year 1936 when this instrument was launched.

[vk6ybavk]

My AVO is a model 8 serial number 6104-C-652. I use this when working on valve radio equipment.

Thank you Owen. VK6YBA.