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Old 21st Apr 2018, 12:08 pm   #1621
pmmunro
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Default Re: AVO Multimeter survey

About 150 ACWEECO/AVO multimeters plus some other AVO units, not counting units too far gone to ever be likely to be working meters again, but kept as a source of parts. Of course they're mostly for research, you'll understand, which means a few "other makes" are needed for comparison. And of course, a couple of decent quality modern multimeters for calibration purposes.

There are still a few gaps in the collection such Models 14, 15 and Heavy Duty Mark 6.

It's unlikely that museums would hold large collections except perhaps eventually Megger themselves. Curators are not often enthusiasts of what they would see as such a narrow area of interest. My concern in general, which I hope will not ever apply to Megger, over company collections is that it only needs a change of managing director/chief executive and the whole lot can end up in a skip with strict orders that nothing is to be removed. "We don't want old junk like that spoiling our modern image"!

It's not a new phenomenon; it happened more than once at Swindon works for example. Important historic locomotives were scrapped because someone "needed the space". I don't think it applies to works of "art" however.

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Old 21st Apr 2018, 4:00 pm   #1622
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I don't know how many I have, I'm still entering them into my spreadsheet as well as Jeremy's spreadsheet. I've got a mixture of ACWEECO/AVO, AVOs of all sorts, full size ones, minors, multi minors, clamp meters, accessory sets.
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Old 21st Apr 2018, 9:23 pm   #1623
AndyGilham
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Well, as the spokes person and employee for Megger on this forum I will say a few words
I have worked for megger since 1994 (actually employed by Avo International Ltd) and still likely to be for the next 30 years. The company is growing, and that comes from having such an incredible history behind us with Donald Macadie's Avo and Sydney Eversheds Megger and everyone else involved.
I am a member of the design team and additionally, through personal interest, very heavily involved in the companies history. Our factory in Dover is soon to go into some huge developments to improve all aspects, and I have personally,conversed with my managing director and architect to include a museum. This will happen, and is intended to be available for the publics visit. It will be a place I will run, control and add to; we want to make a fantastic collection (which is already growing). We do receive instrument donation on occasion, and that's fantastic. I think owners like to know there old products will be on display!
Anyway, that's my little bit. I hope my words give you a little peace of mind that those instruments will not end up in the trash heap Peter.
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Old 21st Apr 2018, 9:36 pm   #1624
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That's really great news Andy, and very exciting. Just imagine, an Avometer museum with a display hall 100 metres long with its walls lined with Avometers from floor to ceiling, all wired up and reading the same voltage! Visitors could use an interactive display where they turn a knob and a thousand Avometer dials all respond accordingly.

I may be having a flight of fancy. However I have a few restored Avos that I'd happily donate to such a cause.
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Old 21st Apr 2018, 11:04 pm   #1625
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Yeah, it's good, a company that is proud of it's past rather than trying to delete it. It's past is no threat to it's future sales. The motor industry could learn a thing or two from that.
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Old 22nd Apr 2018, 1:06 pm   #1626
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Another subtle 'P' prod anomaly which can affect the zeroing of the ohms middle range, particularly if the bakelite knob is a bit loose/sloppy in the facia:

This prod looks fine until you spin it in a power drill at low speed. The thread, although almost perfectly straight, is machined off-centre. When P is rotated this means that the direction and amount of pressure from the battery spring changes, and this can make the wiper move around enough to break continuity.

There was a war on, so i'm not grumbling.
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Old 22nd Apr 2018, 5:32 pm   #1627
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....Just to accentuate the effect of the eccentric thread, in this case the rear drilling and tapping into the knob is cock-eyed, illustrated by the cocktail stick.

Note that not all the brass spikes have this abnormally long thread on, so swapping a long spike into a knob with a short drilling won't work- at least not without modification!

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Old 24th Apr 2018, 10:19 pm   #1628
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Z screw removed from a Model 48A.

On closer examination, the peg is transparent. Under magnification the end had a characteristic shear mark on it, and is therefore apparently..GLASS.

A strange choice when other options were available and easy to fit.. Tricky to reinstall movement!
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Old 24th Apr 2018, 10:27 pm   #1629
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Some very interesting anomalies there that I hadn't come across before. Thanks for posting them, Dave.
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Old 26th Apr 2018, 10:45 pm   #1630
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Default Re: AVO Multimeter survey

Here's a question.

8 mark 5, the Nato Stock number.

I've got two in front of me, both with different stock numbers. Why?

One is 6625-99-620-9572

and the other 6625-99-650-2823.

There appears to be no other difference.
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Old 27th Apr 2018, 6:24 am   #1631
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Default Re: AVO Multimeter survey

NATO, WD, MOD provisioning numbers are many and confusing, and always seem to have been so! At least with Admiralty Pattern numbers you know what it is you're looking at. Your meters may well be identical.

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Old 27th Apr 2018, 6:27 pm   #1632
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Do they both have the same Rev MC latching some would latch others don't. What are the years of manufacture, there may be some minor build standard differences otherwise the buy in configuration of accessories could have different NSN's. I'll have a look next week see if I can find anything but as time goes on a lot of the legacy data is disappearing from the codification systems.
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Old 27th Apr 2018, 9:59 pm   #1633
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The 6625-99-620-9572 is dated October 1977.

I have two 6625-99-650-2823, one doesn't have a date on it and the other is dated September 1985.

All are non latching on the rev mc switch, which I beleive to be the spec for all NATO units, inlcuding the Mk6 NATO units.
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Old 27th Apr 2018, 11:19 pm   #1634
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I'm pretty sure it will almost definitely something in the configuration of the build standard or the supply standard. It could be internal to the meter but believe it or not it could as simple as that in the 70's they were supplied with Mk 1 probes and in the 80's they were supplied with Mk 2 probes.
we have supplied to a number customers previously I'll see if we have the config of the delivery standard and any NSN's used.
I have a few Mk 5's although I prefer to collect Mk 3 & 4's, I'll Check makings on my Mk 5's and see if there are any with NSN markings.
Don't know if I am sating the obvious but:
6625 - the first four digits of an NSN denote the category, known as the Federal Supply Class 6625 = Electrical and Electronic Measuring and Testing Instruments,
The next 2 digits denote the country e.g. 99= UK, 00 &01 = USA, 14 = France, 12 = Germany etc.
the last 7 are the unique identifier.
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Old 28th Apr 2018, 4:48 am   #1635
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I take it you work for Avo/Megger?
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Old 28th Apr 2018, 11:25 am   #1636
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No I work for a company that manufactures aircraft, we also supply the equipment to maintain it including all the test equipment. We therefore have supplied instruction and maintenance manuals for the equipment.
Some organisations we supply work entirely in NSN's so I have some knowledge of the numbering system well that and I'm an ex military aircraft engineer obsessed with Avo multimeters.
I haven't checked my Mk 5's yet, I'll let you know
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Old 28th Apr 2018, 8:50 pm   #1637
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Okay I have more Mk 5's than I thought but could only find one with an NSN (I think I have another boxed away).
The one that I have to hand is a 6625-99-650-2823 and is dated July 79. I'll check the NSN's next week to see if I can find any more detail.

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Old 29th Apr 2018, 3:58 pm   #1638
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Default Re: AVO Multimeter survey

K button versus divide by 2 button (DB2)

Pictured are the components, K on the left and DB2 on the right.

Note that the K leaf has two fixing holes, to prevent unwanted rotation induced by turning the K button. The leaf is stepped. A brass plate is fixed to the base of K, by 2 screws. One c/sunk into the brass, and the other dome head. The dome head acts on the step in the leaf, to enable 'K=1'.

A (phosphor bronze?) spring and ball sit in the side of the K knob, and these sit in detents in the facia bore, at the 9 o'clock and 3 o'clock positions. These detents are not very deep or pronounced, and don't need to be since the spring and ball are very near to the front of the meter facia. The detent grooves give the appearance of having been filed into the bakelite from the front; they are certainly not precisely perpendicular to the front of the meter.

Note that the spring leaf for the DB2 only needs one fixing screw since the groove in the back of the DB2 button prevents the leaf from spinning out of alignment.

I have also pictured the lozenge shaped contact which screws to the rear of the meter facia. (common to both types of meter) I removed this as i wanted to see if it had any rotary adjustment potential..It does not- it sits in a moulded rebate in the facia.

Removing the DB2 button requires care as it has to squeeze past the cutout actuator rod.

Can a K button from a D meter be fitted to a 40 series meter designed for DB2?

Possibly, and especially if the second leaf fixing hole has already been drilled and tapped by the factory; some have, some have not.

I will shortly find out with the aid of one of my parts donor meters, but it should be borne in mind that if one reverses the modification the filed grooves will be just about visible from the front of the meter and would need cosmetic attention.

Converting a K meter to DB2 spec would be a simpler proposition..but personally i can't see the advantage of this mod. (added to which the script on the DB2 button would be confusing)

I did consider keeping this subject dark, but thought- no, sooner or later someone will have the same idea, and modified 'specials' might appear for sale, advertised as ultra rare. Can't have that.

Dave
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Old 29th Apr 2018, 5:12 pm   #1639
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Default Re: AVO Multimeter survey

Dave,

That the two arrangements are interchangeable is highly likely. There are many Type 'D' meters assembled on Model 40 front panels.

The K = 1 or 2 arrangement seems to have been a uniquely Air Ministry requirement, also used on the Minor Type 'E'. The vast majority of Type 'D' meters were made under wartime conditions when materials were directed to whichever factories were deemed by the Ministry of Supply to have the greatest need at the time. I would be very surprised if an Air Ministry supply officer would normally have accepted an "incorrect" front panel except during a wartime emergency.

The vital piece of information which we are lacking is the intended use of the Type 'D'. Its ranges are well suited to auto-electrical work, which would also be valid for aircraft systems of the 1940s. As I have stated before, this would also have made the Type 'D' extremely useful to motor vehicle servicing units of all services but I know of no evidence that it was used by Army or Navy workshops. (Interservice rivalries can run deep). However, some movement faceplates are marked at the top centre with a crown with the letters "A" and "M" at the sides while others have a Broad Arrow (Feon) mark in the same place.

PMM.
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Old 1st May 2018, 9:39 pm   #1640
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Default Re: AVO Multimeter survey

'Hands free' version of Avometer Model 47a, using Model D parts

Success. One very shy Avometer. No good meters were cannibalised during the making of this prototype!

Normal V & A ranges are available with K arrow facing East, Low Ranges are available with the arrow facing West....well almost. I have accidentally engineered the arrow to be 'off' by 5 or 6 degrees- which turns out to be a good thing as it is a visual reminder that the meter should be returned to Normal range after being used. Functions unaffected.

Notes:
Screws on rear of 'K' knob could not be tightened without causing K to be immovable. I settled for medium loctite and just nipping them up very slightly.

Parts used:
K knob, ball and spring, brass disc c/w screws, leaf spring and extra leaf spring screw.

Whenever the back is taken off an Avo with a Q adjuster, the contacts should be cleaned and checked. I would say it's one of the most common causes of annoying intermittency.

Dave
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