AVO Multimeter survey

[The Philpott]

An impressive machine, and you have also stopped someone from making a clock out of it!

Dave

[AndyGilham]

Originally Posted by Sinewave

I picked this up in March. It's in a bit of a state, someone's got at it in the past, so I think it'll just be a display item.

No. 074-1063.

I'd like one of these, so unique looking for an Avo. Don't see many of them around, although there is plenty of the G&E Bradley equivalent.

Andy

[AndyGilham]

I have seen a few adverts and drawing related to this electronic system. Not sure we sold many, so I imagine quite rare.

Andy

[Sinewave]

Originally Posted by AndyGilham

I'd like one of these, so unique looking for an Avo. Don't see many of them around, although there is plenty of the G&E Bradley equivalent.

Andy

Yes I'd had an interest in these, but this one has an open circuit movement, it's very grotty inside and goodness knows what happened to the scale plate.

[factory]

Originally Posted by The Philpott

An impressive machine, and you have also stopped someone from making a clock out of it!

Dave

Sadly a lot of early digital meters never seem to get offered complete or end up destroyed to make a clock, I couldn't let that happen to this one.
I regret not buying another item (not made by AVO) a few years ago due to lack of space at the time, it reappeared a few months later a lot shorter as a clock.

Originally Posted by AndyGilham

I have seen a few adverts and drawing related to this electronic system. Not sure we sold many, so I imagine quite rare.

Andy

There isn't much on the web for these & no service info that I can find, so your probably right about not many being sold, plus the DA112 appeared soon after.
There was another DS109 on a different forum in 2015 but the pictures have since vanished. Also forum member "threeseven" mentions one of these early digital systems in the "AVO/Megger research" thread.

I just noticed the plug is labelled LF Gen, I guess that it originally had that module rather than the multimeter one. The display system frame DS109 is serial no. PP003, anyone know what PP stands for? The multimeter module MM110 is serial no. 205 and the AC option card AC111? is serial no. 173.



Possibly a little OT but do any of the adverts give the models of the other modules?

David

[egrabczewski]

I have three that I'm fixing for myself:

Model 7: No. 7747-36734
Doesn't work on most scales. Looks old inside, everything is painted with that varnish stuff and most resistors look like the coil variety.

Model 7 Mk II: No. 4694-A-1069-M
Works on some scales. Pretty clean and new inside.

Model 7 (but no label on the front button; says "Model 7" on the back): No number on the scale.
Works on all scales after I replaced a resistor. Looks clean and new inside.
My guess is that this one has been refurbished.

[AndyGilham]

The collection grows, today I have received 2 new meters for the collection

Universal Avominor - Serial Number 98172-1246 (December 1946).
This is the 18th Universal Avominor from 1946 on my list, and the second one from December 1946.

Avominor Model E - Serial Number 23213-1945
This is the first Model E for my collection, and the highest serial number in my list of 20.

Both instruments are in a well used condition, having been owned by the sellers father who was a civilian working for the REME.
Purchased on ebay for just £12 the pair

Andy

[Superscope]

Hi egrabczewski,

Thanks for your Model 7 Serial Numbers.

Could you give us some futher information to help with the Survey?

Model 7: No. 7747-36734

Does this Meter have the Horse Shoe Magnet, Meter Movement ?
Does it have an Alloy or Bakelite rear Case ?
If it is an alloy Case, does it have the Black Crincle Paint finish or another Colour?

I think this Meter is to early for PF sockets, but I have to ask.
Never safe to assume anything in this Avo Meter Game.


Model 7 Mk II: No. 4694-A-1069-M

Does this have an Alloy or Bakelite Rear Case?
If alloy, is it a Black Crincle Paint Finish or other Colour?
Does it have PF sockets?

Regarding the Model 7 without a Serial Number, is this the one with a Blank
position instead of a White Dot as mentioned on your other Post?

I think this is likely to be a late Model 7. Some Photos would help to confirm this.
If your lucky, sometimes, the Serial Number is writen in Pencil on the Meter Movement
during repairs although this practice was less common during later years.

Later Meters with the Labels on the outside rather than printed on the Scaleplate, often have the Labels removed!
Can't imagine why that would be!


Ian

[Superscope]

Hi Andy,

Does your New Avominor Model E - Serial Number 23213-1945
have an "E." at the begining?





Ian

[AndyGilham]

Ian,
yes it does indeed have the E at the beginning

Andy

[Superscope]

Thanks Andy,

I thought it probably did, but always pays to double check everything.


Now, can you tell us more about the "Hidden Dotty Range" on the Model 7's ?
What's that all about?

I didn't want to Hijack the other Thread, so thought I would ask you here.

On my 1946 Model 7, the AC Dot is definitely not connected to anything.
All the other Model 7's I have (With the Dot) which are much later, do exactly
as you say. 31mA FSD give or take.

The much later Model 7's without the Dot (Just Blank) don't seem to have this feature.

Can't imagine what use this was intended for.
Was there an accessory that used it?



Ian

[AndyGilham]

Ian,
This 'Dotty' range was covered previously in the forum, and so I am only quoting.

Basically its an AC range with 31.62mA fsd, which seems a strange value, but in fact 3.162 is the square root of 10. With this you can measure current through a resistor because The power in the resistor (i-squared R) can be easily calculated from the values indicated on the linear scales.

Andy

[The Philpott]

...and almost as useful as the 10mA AC range included on the Mod 9/II.
Dave

[Phil G4SPZ]

Originally Posted by AndyGilham

Ian,
This 'Dotty' range was covered previously in the forum...

I looked this up to refresh my vague memory, only to find it was me who actually posted about it back in 2014 in post #5 here!

[Superscope]

Thanks Phil,

Amazing what Gems of Information are hiding away in this Forum.

I vaguely remember reading about the Dots somewhere, probably here,
but had forgot about it, and/or never read it all.

Andy's comment on the other thread got me interested.




Ian

[The Philpott]

...This prompts me to mention that a Model 7 with that logarithmic over-scale attached to the Q knob appeared on ebay much more recently than 2014. The photos were quite poor but i did scavenge an image from it. I will dig it out at some point over the next few days.

Dave

[pmmunro]

This image is a direct scan of a 'Q' Disc. The inner hole is 1/2" diameter and the overall diameter is 1 1/4".

The first scale mark is '3' and the last one is '50'.

The millimetre comparison scale is probably useful for any image processing but if anyone wants an inch scale, please let me know.

PMM

[Phil G4SPZ]

Thank you for that, Peter. A little bit more definitive knowledge is added to the canon of Avometer lore.

Now we need to see the circuit and some pictures of the insides of the elusive Power and Decibel Range Extension Unit! At least one is known to exist, in Paul Adams’s collection. There must be others...

[6.3volts]

Four more devices to add to your database;
1: sn 102024 869 says Mk8 on the back. 10&2.5 scales This was my first Mk8 and has been in occasional use for a couple of years.
2: sn 55938-C-157 8X mk2 panclimatic without a metal case. 10&2.5 scales Brown bakelite. Working.
3: sn 8423 670, (RPO 7/74 written on the lower front scale). Panclimatic with metal back shield. Testset No1 High Sensitivity. 10&3 scale Severe corrosion from batteries continuing into the instrument. May well be repairable.
4: No serial number on the scale. Listed on the back "model8". 4 black terminals without sockets and no 500v switch position. 10&2.5 scales Brown smoke staining on the centre of the scale but meter has continuity so it may have been replaced. One of the current shunts is toast so I suspect an owner repair by movement substitution. The scale may be original. Possible candidate for restoration.
Any idea how I can determine the date?

Hope this is of interest, Jonathan.

[The Philpott]

Hi Johnathan, your meter No.4 will almost certainly be within 1951-1956 date range; it is the first iteration of the Model 8. Difficult to be more precise than this!

It may be possible to lessen the smoke staining on the scale with a cotton bud soaked in wd40, but probably not remove it altogether.

Dave