AVO/Megger research

[AndyGilham]

Good evening Enthusiasts.
My name is Andy Gilham and I have been working for AVO/Megger in Dover for the last 22years as a mechanical design engineer.
This year (2016) Megger has/are celebrating 50 years in Dover, or at least 50 years since the factory was opened. To celebrate this, the company is holding an Open Day on Saturday 12th of November (2016).
I have taken on the task gathering history of the company, this includes a display of almost all of the AVOmeters, including a lovely Model 1 (1923) in wooden case which we own. I have also been working with Richard Allan (of RichardsRadios fame) who has kindly let us many of his own collection for the day.

I am also collecting data and photos which are being detailed in a AVO/Megger history document we shall be giving out on the day. I have a lot of data from our archives, but this forum has been offering me a lot more...! Thank you.

One of my former colleagues, and friends retired 4 years ago. He moved down to Dover from London when Vauxhall Bridge staff moved, and was heavily involved in the Model 8 Mark 4, Mark 5, Mark 6 & Mark 7 designs, so I shall be picking his brain on some details about the products.

I have access to the original tape master pcb, and hand drawn schematics. I have all the original drawing sets for each part within the product. I have even found the original Macadie patent for the Model 1
In fact I myself did a redrawn and artwork print of the 8Mk7 scale plate (10 scales were printable, and the scale was selected based on the movement balance).

So, I hope to offer a lot more information to this forum over time....once I have all the information.

Regards
Andy Gilham

[Refugee]

I have got a wooden Megger and have been told it is a model 1.
It is still used in a semi fixed location with an external battery and voltage converter making it a little bit portable.
I did a thread on it some time ago.
http://golbornevintageradio.co.uk/fo...d.php?tid=3637

[The Philpott]

Thank you Andy, and I hope the recruitment aspect of this goes well for the company.

As far as the History Display goes it is a bit far for me to come, but I probably speak for several when I ask if the history document could be submitted to this forum afterwards so that we can peruse? Perhaps a moderator could comment on the best format.

I have been researching early rare meters such as the Low resistance ohmmeter and the HR DC Avominor, partly with the objective that people who do not own them in their analogue toolkit or collection can at least see HD images rather than catalogue line drawings of the period.

Many thanks
Dave Philpott

[emeritus]

No hardware, but I have a couple of pre-First World War GEC catalogues with illustrations of Meggers that I can scan.

[hilitevr]

Hi Andy,

I have a 1923 model 1 in quite poor codition see photo.

Any imformation you can post on this model greatly appreciated.

[The Philpott]

Trevor i would describe that as ok condition. I would expect the brass screws to be siezed into the alloy casting- need a good soaking if you ever give it a light refurb.

(Is that a price tag on the handle? Only kidding!)

[Dekatron]

I just found this, maybe it is of interest to you: http://www.aef.se/Matteknik/Dokument/Miljonte_AVO_8.pdf the text translated into English is (maybe some errors):

In the presence of Eng. S. von Melstad, leaves the Ambassador G. Hägglöv the millionth AVO meter to Eng. C-R Ekblad.

The attention from AVO against FV (FlygVapnet = Air Force)

For the Great Exhibition in London - called Radio and Electronic Component Manufacturer Federation Exhibition - had the English firm AVO produced and delivered the millionth AVO meter. The first in the series was produced in 1923 and got its name from the first letters of the three basic electrical quantities amps, volts and ohms.

At a lunch in this connection, when the Swedish Ambassador Gunnar Hägglöv was the guest of honor, handed him the AVO Ltd's behalf this millionth instruments Chief Engineer C-R Ekblad. The latter, who CVA bill, visited the exhibition on vacation, thanks to well-chosen English words for the gift of the CVA and the Air Force's behalf, the Avometer represents a high standard of universal instruments not only in England but also in 100 other countries, and the company supplies abroad has tripled over the past three years. The instrument was demonstrated during the family day.

[threeseven]

Really wish I'd seen this in time to make the open day
I have a modest collection of Avo's, including a relatively unknown digital system that used a common display unit which could be used with various modules to make a range of instruments.
The traditional Avo meter is an icon which is finding an ever increasing following of enthusiasts.
Would there ever be a chance of a legacy program for spare parts for the obsolete Avo's?

[The Philpott]

Threeseven- I think we're fortunate that the factory was so prolific in the first place- as far as parts drying up i haven't- so far- had to condemn one for lack of spares!
The leads and attachments are still turning up, some of them NOS, but the leaf switches and the movements are a sticking point (pun intended)
I have a box of 5 donors which are in various states of degradation, and if it wasn't for these none of the 'good' ones would be working- anything to save them from ending up as steampunkretroartdecofartyartefacts.

Is your collection in the AVO survey on this site?

Dave

[threeseven]

Two things I need to bring an 8 Mk5 back into use are the rubber bellows around the cutout and reverse buttons, and the plastic escutcheon around those buttons and the adjustment knobs. The escutcheon has to be removed to access the rubber bellows, which destroys the escutcheon, or so I'm led to believe.
What about meter magnets? They are eventually going to fade.
I have mentioned a some of my collection in the survey but I don't have any images or a list.

[The Philpott]

I take your point on the magnets, i have only ever been able to get a small variance in deflection on the rare occasions when i discovered the shunt had come loose and was flopping around. However, I have not (yet) had problems with 70 year old ones going beyond the limits of their compensation. I would be interested in the difference in longevity between alnico and the other composition/s used.

The accuracy/cost of remagnetization rather than the issue of having it done would be our main concern! It sounds like you have more recent meters than i have been involved with but best of luck with the parts needed.

[jez_145]

threeseven,

I know discussing repairs is a bit off topic for this thread but I've found that removing the label on the front panel of an 8 MkV (when replacing the Cut-out and Rev MC Rev rubber shroud) is not too difficult and can be done without destroying it. I used a hairdryer to warm it up (and the adhesive underneath) and gently eased it up using a thin plastic spreader that came with some Araldite. The important thing is not too bend it too much and kink it. Just take your time and keep it warm. The old adhesive under the label and the front panel can be removed with meths afterwards. After replacing the rubber shroud (if you can find one !) just glue the label back again with rubber adhesive or similar.

I've repaired a couple of Mark V's now (including a "pre-shroud" model) but, I have to say, I much prefer working on 8 Mk3 and earlier instruments !

Jerry

[Refugee]

Originally Posted by AndyGilham

including a lovely Model 1 (1923) in wooden case which we own. I have also been working with Richard Allan (of RichardsRadios fame) who has kindly let us many of his own collection for the day.

Could you post a photo or two of your model 1 as I would like to see if it looks anything like the wooden Megger I own?

Cheers.

[threeseven]

Originally Posted by jez_145

I know discussing repairs is a bit off topic for this thread but I've found that removing the label on the front panel of an 8 MkV (when replacing the Cut-out and Rev MC Rev rubber shroud) is not too difficult and can be done without destroying it. I used a hairdryer to warm it up (and the adhesive underneath) and gently eased it up using a thin plastic spreader that came with some Araldite. The important thing is not too bend it too much and kink it. Just take your time and keep it warm. The old adhesive under the label and the front panel can be removed with meths afterwards. After replacing the rubber shroud (if you can find one !) just glue the label back again with rubber adhesive or similar.

Thanks for the tip. If I find a rubber shroud I'll have a go at it! The meter is mint apart from that. Most of my collection is earlier but I wanted a Mk V as an example of the last'ish of the line!
The earlier versions are definitely more repairable and maintainable.
I also have some of the way more recent analogue Avo's, of the 1000 series, and a 90's Avo DMM, which is a very good instrument.

[AndyGilham]

Sorry for the delay replying

Refugee: I have attached the image of my AVO (Model 1)

Refugee: The links to the images you attach seem to be for the Evershed & Vignoles moving coil ammeter, which would probably date it before Macadie's AVometer (Model 1)


Dekatron: An interesting Article, thank you. What is more interesting is the reality. During my investigation here at Megger, I got talking to a chap who was working on Avometers in the 1965, see the photograph attached of him at the front of the image from January 1964 (Before the main factory was open). He actually owns the real millionth avometer. The one handed out in the article was 1 of 5 manufactured as a millionth meter, but he owns the actual serial coded 1 millionth, and has it still unopened in its original packing box (he is now retired).

The Philpott: During my writing of the Avo/Megger history, i have looked at some of the more unusual products myself and wrote sections on the AVO Low Resistance, Avo Heavy Duty, DC Avominor.... and even a section on the interesting AVO Exposure Meters.
The booklet I wrote for the open day was a great success and we had 500 printed on site, of which 460 were handed out. There are a few errors within it, that would be picked up in seconds by the clever folk on this forum, but I had limited time to complete it all. However, the Managing director was so impressed he has asked me to continue adding and editing and its become a second job for me!.


Regards
Andy Gilham

[Dekatron]

It's a like Schroedingers cat with the millionth AVO, you don't know if it is the one until you open the box.

Does the story tell who got the other three "millionth" AVOs?

Will the booklet be released as a downloadable PDF?

[Refugee]

Originally Posted by AndyGilham

Refugee: The links to the images you attach seem to be for the Evershed & Vignoles moving coil ammeter, which would probably date it before Macadie's AVometer (Model 1)

Mine is definitely not an ammeter. It is clearly a 500V Megger for use with an external power supply. I use it regularly with a little battery powered DC-DC converter that lives on the power input terminals.
It is certainly an early one and it also more accurate than one would expect for such an early instrument.

[Pamphonica]

Andy,
is that a copy of the original artwork for the plate on the "Model 1"? I have a Model 1 that I have restored to good condition and working order but it is sadly missing the nameplate. I checked it against a voltage standard the other day and it's about 1.5% out on DC Volts. All ranges work - not bad after over 90 years!
If you could send me a file with the plate information that would be helpful. I still have no idea how I would get such a plate etched or whatever but at least I'll have the info if I need it!
By the way, PMMunro on this forum is very much the guru for early Avos as far as many people are concerned. You may wish to contact him via PM.
Good luck with the research.
All the best
Jeremy

[The Philpott]

Thanks for pics Andy, i would be dead interested to see your booklet text (particularly regards the low resistance ohmmeter, of which two examples are now known to me)

Dave P

[AndyGilham]

Dekatron: Definetely a Schroedingers cat situation yes...! Sadly I have no idea where the remaining instuments went. I imagine the managaing director at the time had one.
The PDF booklet is 20mb, so I will need to find somewhere to upload it. But i would like to make a few corrections first and add some extra sections.

Refugee: I can see from the images now thats its not an ammeter. I was not able to few them previously, as they were linked from another forum. the Voltmeter and Ammeter were in very similar wooden boxes.

Pamphonica: Yes, the image I uploaded was the plate from my Model 1. It was not a great photo, so i generated the text image to make reading it clear.
I have had a couple of phone conversations with Peter Munro, and he have discussed some of the history. He gave me some useful information on dates and patents to clarify my own findings. Thank you.

The Philpott: I will try and get the information uploaded at some point. You are right though, very little is known about these LRO products. I think because they were introduced just before the WW2, production was ceased to concentrate on the war effort and the manufacture of the Avometer.


Regards
Andy Gilham BSc Hon.