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Old 11th Oct 2020, 10:02 am   #2701
Superscope
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Default Re: AVO Multimeter survey

Ref Post #2698

That is an interesting Meter.
Not because it is a Model 2, as there are quite a few surviving examples
of Model 2's, but the Serial Number makes it one of the very last Model
2's manufactured.

I had previously estimated the last Model 2 to be around Number 6250, so
this particular meter pushes the estimate up by a margin.

6317 would have been very close to the end of Model 2 production, since the
Model 6 had started production by at least 6394, only 77 Units later.


It's a shame that it has been modified though.
Assuming it is modified, but this is something I have seen before on Model 2's.
I suspect this type of Modification was quite common back in the Day.



This brings me quite nicely onto some research I have been doing recently.


I suspect that, in addition to owners carrying out their own modifications
to Model 2 Test Leads, that Avo themselves offered the same Modification by
substituting the Case from a Model 6.

I am now aware of at least Two examples of Model 2's which reside inside
Model 6 Cases.

First impressions have been that Owners have swapped over cases to repair
broken Meters. Something that is still done today.

However, the Model 6 Cases on these Hybrid Meters have been professionally
changed with plugs blocking the /2 Button Hole and External Voltage adjust Hole.
Both of these Hybrids have the same identical Modifications, so clearly carried
out by the same Company, which almost certainly can only be Avo.

I will post the Photos of these Hybrids Meters after I've checked with the respective
owners.



Ian

Last edited by Superscope; 11th Oct 2020 at 10:16 am.
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Old 11th Oct 2020, 3:04 pm   #2702
Aitor Eneko
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Default Re: AVO Multimeter survey

Congratulations for your find Andy.

Very interesting these hybrids meters, Just waiting for the photos.

Thanks
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Old 11th Oct 2020, 6:05 pm   #2703
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Default Re: AVO Multimeter survey

I don't think Andy's Meter is a Hybrid in the true sense.

It's just a Model 2 which has had some Terminals added.

The Test Lead Bridge is still present in the middle of the Panel,
so it definately has a Model 2 Front Panel.

The Hybrid Meters I was refering too previously, are Model 2 Meters
which have been transferred into Model 6 Cases.
By Cases, I mean the Alloy Case and Front Bakelite Panel.
I didn't make that particularly clear earlier on.

The Model 6 front Panels on the Hybrid Meters, do not have the Central
Test Lead Bridge normally found on Model 2's.

They are identical to the Model 6 Panels, but have the Divid by 2 and
External Voltage adjustment holes filled with what looks like a light coloured
Bakelite or Plastic plugs.

The Data Plates surprisingly also appear to be Model 6, but clearly some
of the functions are not possible with just a Model 2 interior.

It looks to me, like broken Model 2's may have been returned to the Factory
for repair post 1936, and ACWEECO only had Model 6 Cases/Panels available
to affect a repair.

It is also possible that ACWEECO supplied modified Model 6 Cases for
Owners to repair (or modify) their Model 2's themselves.

We might never know the full details, but the Modified Model 6's Panels do
definately exist.



Ian
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Old 12th Oct 2020, 5:39 pm   #2704
AndyGilham
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Default Re: AVO Multimeter survey

Well that threw me, I never even picked up on the fact this has terminals fitted. So, out of curiosity I open the instrument up and was shocked to find something missing!
Yes, the Rheostat is missing and the red wire shows the new terminal shorted directly to the range switch.

Now the seller told me the instrument works perfectly and makes measurements! But I have to assume it ignores current? Any ideas on how the schematic has been adjusted for this?

Andy
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Old 12th Oct 2020, 5:45 pm   #2705
AndyGilham
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Default Re: AVO Multimeter survey

Since I am here..... I have another meter, the Avo Multimeter type H.I.108 (High Impedance). This instrument was developed in 1964.

So I got home to a package having been delivered to my home address, and this was inside. I have no idea who sent it, or where it came from. There was also an Evershed & Vignoles Series 3 hand crank insulation tester. However sent it, I am grateful, as its a nice addition to the collection

Regards
Andy
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Old 12th Oct 2020, 6:20 pm   #2706
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Default Re: AVO Multimeter survey

Hi Andy,

It looks like the Rheostat has simply been removed
and replaced by a that piece of Wire.

It doesn't look like any modifications have been made
in addition to the Wire Link.
Other than the New Terminals of course.
The original Terminal connections can still be seen in the Center of the Panel.

The Rheostat is supposed to be taken out of circuit
for current measurements over 1.2 Amps, hence the
"Off" position.

I guess somebody forgot and burnt it out rendering
all current Ranges in operative.

Why they didn't just leave it in and bridge it, who knows.
They are quite thick windings and should have been quite
straight forward to repaired.

I'm not sure how this will effect Current measurements
below 1.2 amps.

PMM will probably know the answer to that better than me.


Ian

Last edited by Superscope; 12th Oct 2020 at 6:27 pm.
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Old 15th Oct 2020, 9:07 pm   #2707
The Philpott
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Default Re: AVO Multimeter survey

An Avominor type HR has just appeared for sale; i have no ambitions to buy but am trying to get the serial number from the vendor to expand our knowledge of the production run.

Dave
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Old 19th Oct 2020, 4:17 pm   #2708
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Default Re: AVO Multimeter survey

I added a small batch of Serials Numbers today and the
Survey has now reached a Milestone.


We have now just gone over the 2500 mark!
2502 to be exact.



Ian
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Old 19th Oct 2020, 6:22 pm   #2709
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Default Re: AVO Multimeter survey

I got a bit behind so here is an update on new ones I have (or had).

Ian, I will email a complete checklist to you directly in case we are out of sync. What amazing work you are doing to keep alive the original work by SpCh.

DA114 B1708 1976
Model 12 707-763 1963
DA114 B1454 1975?
Model 12 2316-767 1967
Model 7 Mk2 45725-A-1153 1953
Multiminor Mk 5 32919 1967
Model 9 Mk 2 17878-569 1969
Model 47A 18368-245 1945
Model 8 Mk2 82194-C-1158 1958

All best
Jeremy

(Now down to a mere 31 Avos in my core collection, plus 11 to be sold or traded and 15 already sold. Making progress!)
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Old 19th Oct 2020, 8:37 pm   #2710
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Default Re: AVO Multimeter survey

I picked up a second AVO DS.109 Digital System with M.M.110 Multimeter Module last Friday, serial numbers 239 (DS109), 249 (MM110).
To my surprise it also has the AC option installed, the selector mechanism was jammed making me think it wasn't fitted, SN 233 (AC111).

They must have quite a few of these as the mixer/timer/trigger PCB has been redesigned, (I need to check but I think it was a double sided PCB in the older one and single sided in this one).

The reference cell isn't completely dead this time, it's down to around 960mV, from the 1.01925V on the Muirhead paperwork inside.

It needs some repair work as it currently only displays zeros, hopefully I will be able to use the other to narrow down which PCB's are faulty, as I've not seen any service info for these (the other only works in manual trigger mode).

David
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Old 24th Oct 2020, 8:43 am   #2711
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Default Re: AVO Multimeter survey

As promised, here are some Photos of the Model 2/6 Hybrids.


Photos 1 & 2 courtesy of Jeremy (Pamphonica)
Photos 3 & 4 courtesy of George (Not a Forum Member)


Jeremy's Meter, which has been known to the Forum for some time,
has clearly had a later modification to the Fuse.

George's Meter has had a later replacement of the Terminals, with a
non-standard type.


These Hybrid Meters use genuine Model 6 Front Panels.
The Panels have been Modified in the following way:

1. Divid by 2 Push Button Hole has been blanked off with a Resin Plug
2. External Voltage adjustment Hole has also been blanked off with a Resin Plug.
3. Embossed Labelling on Central Section detailing the /2 function has been removed.

These Modifications have been done Professionally and exactly the same way.
The plugs are not roughly made items, they are sculpted and high quality.

The Meters are pure Model 2's internally.

Jeremy's meter retains the Model 2 Dataplate and back Case, but
Georges seems to have a complete Model 6 Back Case and Dataplate.



So, the Hybrid Model 2/6 Meters clearly exist in their own right.

It was not, a one off Conversion done by a previous owner.
There was clearly a professional element involved in these.

Why would this have been done?

A Model 2 Avometer would have been quite an investment in Equipment in the
1930's. Probably to expensive to just Throw away because of inconvenient or
Damaged Test Leads.

Who would have done it?

Either the Model 2's were returned to ACWEECO to carry out the Conversion/Repair, or
ACWEECO supplied Modified Model 6 Case Kits for Owners of Model 2's to effect their own Repairs.

We probably won't know who did the conversions unless new Documentation is forthcoming, although
the fact that one of these Meters has what appears to be a Model 6 Rear Case with a Dataplate which
clealy won't be relivant to the limited functions of a Model 2, might suggest that the Front Panel and
rear case were bought as spare Parts, but not necessarily together.

Interestingly, the Model 2/6 Hybrids are even Rarer than the Model 6 itself.


Ian
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Last edited by Superscope; 24th Oct 2020 at 9:00 am.
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Old 24th Oct 2020, 10:21 am   #2712
Radio Wrangler
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Default Re: AVO Multimeter survey

On the subject of hybrids....

Back in the early 70's there were adverts in WW, PE etc offering new AVO 8 movements which were surplus spares. (6-19/6 if I remember)

Then in wireless world, there was an article on making an electronic multimeter around such a movement.

So there have beed some wilder hybrids based on AVOs.

David
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