AVO Multimeter survey

[The Philpott]

Re. Post No.2100- That was my thinking exactly! June 1939?

[Aitor Eneko]

I have one exactly like that model 5 with "plastic" screws

[sparkymike]

Another one for the record.
Model 40 Mk.2 No. 512 - B- 1266
Metal case (Silver, very similar to the Quad 11valves amps.)
Complete with probes in wooden box, looks to be original with thick grey white felt padding.
Any idea on year of this one from above numbers ?
Photo later.
Mike.

[Sinewave]

December 66?

Not so sure the box is original.

[Phil G4SPZ]

Andy Gilham has contacted me regarding his Model 7 serial number 15629-A-550 which was made in the same month as my example, 15217-A-550. I’m attaching a few pictures of my meter here, in case they may also be of interest to anyone else.

I’d just like to point out that I bought this meter in good faith on eBay and did not ‘liberate’ it from the original owner! The company name appears to have been moulded in at the Avo factory.

Phil

[AndyGilham]

Thanks for the images Phil, looks identical to mine....as one would expect! So no repair mods there!
I got my Mod 7 for £20, and it pretty good condition. I will get some images.

Phil, During the 50's and 60's, Avo were supplying movement assemblies to Marconi, that were used in their own equipment, I wonder if that same movement was used in The Model 7 you have. I'll need to investigate the differences from the standard Avo movement.

Andy

[Phil G4SPZ]

Originally Posted by AndyGilham

So no repair mods there...

Ah, so you didn’t spot the two modern resistors in series that I fitted to replace an open-circuit resistance range winding?

As far as I can see, Andy, the movement is no different from normal. The serial number “15217” appears in pencil on the rear of the scaleplate, but there’s a different five-digit number on the back of the magnet assembly. I’m not sure you can see it in the photo, but it reads “46305”.

[AndyGilham]

Ooh yes I think I see them, just below the wound coils!!?
I also like the fact that these instruments have a tiny little extra shunt board added in.

Ok so maybe it is standard. I will look into the archives.

Andy

[sparkymike]

I have seen an additional oblong moulding that fits to one end of the meters, to carry the probes. Were these an optional extra , or only fitted to some models. Do they turn up on auction sites?
Given or loaned a pattern, I could mould new ones easily I believe.
Can someone post a photo of one please. (Front and rear view.)
Mike.

[Pamphonica]

I couldn't resist rescuing an Avo 8 Mk5 at £1 from the inaugural TNMoC electrojumble at the weekend. Marked as faulty, the needle did move but stuck mid-scale. On opening it up I saw that the magnet centre pole was definitely not centred. A gentle lever with a non-metallic screwdriver remedied this. It must have taken a good knock but suffered no cosmetic damage.
After a couple of days of gentle to-and fro exercise on the movement using a function generator at 0.1Hz all is moving smoothly once more. The initial slight errors in returning to zero are virtually gone.
I have re-attached the ripped-off battery connections and only have the 1x ohms range left to fault-find.
Otherwise it's about 0.5% low on readings - not bad for £1!

Avo 8 Mk5
Serial number 99842
Marked 8V/11/73 so Nov 1973 I assume.

-Jeremy

[AndyGilham]

As promised, please find attached a few pics of my latest Avometer Model 7 (May 1950). this was the early model 7 panel that incorporated the PF sockets. Notice the small sub-pcb with the 20k ohm PF resistors fitted.

Andy

[AndyGilham]

Originally Posted by Phil G4SPZ

Andy Gilham has contacted me regarding his Model 7 serial number 15629-A-550 which was made in the same month as my example, 15217-A-550. I’m attaching a few pictures of my meter here, in case they may also be of interest to anyone else.

I’d just like to point out that I bought this meter in good faith on eBay and did not ‘liberate’ it from the original owner! The company name appears to have been moulded in at the Avo factory.

Phil

Interstingly, although the same model made in the same month, your top resistance board seems to only include 3 wound coils, whreas mine has 4, or is this where your resistor modification comes in, is it a replacement for that coil?

Andy

[Sinewave]

Originally Posted by AndyGilham

As promised, please find attached a few pics of my latest Avometer Model 7 (May 1950). this was the early model 7 panel that incorporated the PF sockets. Notice the small sub-pcb with the 20k ohm PF resistors fitted.

Andy

It's always intrigued me as to whether these early ones with the PF sockets are still a Mk1 or a Mk2?

[AndyGilham]

I consider them a mark 1, but it was clearly a transitional period. The front panel plug and instruction plate both states Model 7......so lets go with that!

[Sinewave]

Indeed, the Mk1 terminal posts and as you say, it says Model 7, not 7 Mk2.

So Mk1 it is!

[The Philpott]

I believe the PF sockets were an optional extra on the Mk.I

Dave

[AndyGilham]

Possibly, but not an option many user went for! Not seen a lot of these variants about, with the model 7 panel. I have a feeling the mould tool was modified to include the extra sockets, but near the end of its life, prior to the mk 2 being launched. Then it was a new panel with fully incorporated PF sockets.

Andy

[Phil G4SPZ]

Originally Posted by AndyGilham

...your top resistance board seems to only include 3 wound coils, whereas mine has 4, or is this where your resistor modification comes in, is it a replacement for that coil?

To be quite honest, Andy, it was so long ago and I was repairing so many Avos at that time that I simply can't remember the details of the repair However I think you're right, I most probably replaced the end bobbin with the two fixed resistors in series to get the exact value. I would imagine our two instruments were identical when they left the factory.

EDIT: I actually posted the serial number of this meter on 25th February 2008, right back on page 6 of this venerable thread! I think it may have actually been the first Avometer I acquired. Looking through some old closed threads, I now remember a bit more about this meter - the movement was faulty, due to the acceleration cut-out having come detached from the moving coil. I think it took me a couple of years to get round to it, but I eventually succeeded in repairing the movement. I wrote a Success Story about it at the time. The one open-circuit bobbin was the least of my problems!

[Sinewave]

Originally Posted by AndyGilham

Possibly, but not an option many user went for! Not seen a lot of these variants about, with the model 7 panel. I have a feeling the mould tool was modified to include the extra sockets, but near the end of its life, prior to the mk 2 being launched. Then it was a new panel with fully incorporated PF sockets.

Andy

Luckily I have in my collection a model 7 and a model 40 mk1 with the pf sockets.

So there are at least three of the 7 and 40 models for an essential collection.

[sparkymike]

Photos showing pristine inside views of my Avo re. my post of 23rd. this month.
Battery terminals needed cleaning, but don't they always !!
Mike.