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Old 11th Oct 2020, 3:04 pm   #2701
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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   #2702
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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   #2703
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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   #2704
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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   #2705
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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 Centre 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

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Old 15th Oct 2020, 9:07 pm   #2706
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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   #2707
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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   #2708
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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   #2709
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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   #2710
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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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Old 24th Oct 2020, 10:21 am   #2711
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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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Old 27th Oct 2020, 11:24 pm   #2712
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Default Re: AVO Multimeter survey

Just been given an AVO8 Mk3, s/n 46785-966. Complete with leads, probes and clips, all in very good nick!

Colin.
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Old 31st Oct 2020, 10:29 pm   #2713
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Default Re: AVO Multimeter survey

DC Avominor Type HR - s/n 162-108 (October 1938)

I did mention the appearance for sale of this meter in the hope that someone else would buy it, (i failed to get the serial number from the seller) but ultimately the asking price dropped so far that my intention to leave it alone evaporated!

The serial number caused a double-take as i already have s/n 168-108.
It came with the usual box and leads, but the instructions are for the standard DC Avominor, and i will pass them on.

Both factory seals (complete with anti-tamper logo) are present on the two rear (recessed) grub screws- which is a bit of a shame as the 50kohm bobbin is o/c, disabling the 2.5v range, leaving all the others in operation as the meter is not arranged with a normal series shunt chain. The basic calibration (sampled using the 10v range) is very good considering it has probably never been opened since new- half-scale is 1% of FSD low, full scale is almost dead-on. Normal non-linearity!

If i do decide to disturb the seals (by no means decided as, for once, the glass is not rattling) i will attempt a photo of the logo, and sketch it.

Dave
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Old 1st Nov 2020, 11:50 pm   #2714
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Default Re: AVO Multimeter survey

Dave
I was certainly tempted by it, but I already have 2 HR in the collection.
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Old 2nd Nov 2020, 8:02 am   #2715
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Default Re: AVO Multimeter survey

Dave,
You mention you have HR 168-108, on my list you also own HR 206-108, is that correct?

Andy
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Old 2nd Nov 2020, 1:33 pm   #2716
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Default Re: AVO Multimeter survey

Nice one Dave,

Great to see you still exercising Self Control !


I have HR 206-108 listed as owned by another Forum Member.
Unless Dave has secretly bought it.


Edit: Just looked, and yes, looks like Dave does now own it.




Ian

Last edited by Superscope; 2nd Nov 2020 at 1:45 pm. Reason: correction to comment
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Old 2nd Nov 2020, 7:26 pm   #2717
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Default Re: AVO Multimeter survey

Hi Ian, my book says that 206-108 is owned by 'Micheal'. This info could be out of date but i somehow doubt it he would have disposed of it!

I did a more exacting calibration test of s/n 162-108 paying more attention to the zeroing (and in better light) and returned a reading of 9.9v on the 10v range using a 10v AD584 reference source- that is a seriously stable magnet!

Dave
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Old 2nd Nov 2020, 7:41 pm   #2718
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Default Re: AVO Multimeter survey

Thanks Dave,

Yes, I had it logged against Micheal from 2009.

You reported it again in 2017, so I thought you
may have bought it.
That might also be why Andy thought you owned it.

I think we can safely assume then, that Micheal
probably still has it.



Ian
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Old 2nd Nov 2020, 10:28 pm   #2719
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Default Re: AVO Multimeter survey

Andy/Ian

-i know what happened- at the time i submitted data on all those Type HR's that i knew of!

These don't belong to me:

144-98
206-108
404-79
509-640
566-141

I have yet to hear of more Low Resistance Ohmmeters (similar period of manufacture to those HR's) beyond the 2 which are logged...but of course they carry a 1.5v cell so wastage could have been higher. We know 375 or more were made.

Dave
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Old 2nd Nov 2020, 10:42 pm   #2720
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Default Re: AVO Multimeter survey

I have two AVOs inherited from my Father; one a Model 7, no 71143-11559 (no letters). Black lead & prods still there but red lead's barrel connector broken off. Bakelite case. This one was around at home in my youth.
The other is a 7 mk2, 75367-A-358, leads rather worn and red sleeve missing, prods & clips present. Metal (hammerite painted) case.
Both of these are on the tuit pile as calibration is nowhere near good.
I also acquired a Multiminor mk5 some time ago, no sign of s/n, leads ok but no prods or whatever else it used to have, A couple of resistors have been replaced and its accuracy is pretty good. This one might be offered for sale at some stage.
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