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Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders.

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Old 31st Oct 2013, 9:59 am   #1101
jez_145
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Default Re: AVO Multimeter survey

A couple more serial numbers for the survey:-

AVO Model 8 Mark 3 Ser No. 19086-665
AVO Model 8 Mark 5 Ser No. 0036290 CB 8V

I'd like to take this opportunity to thank the various contributors to the TEST/AVO discussions for the very helpful info they have submitted. Whilst I have only just signed up as a forum member, I have been studying the AVO related threads for sometime and have learned a great deal from them.

My Model 8 Mark 3 was already in pretty good shape when I acquired it earlier this year. However, after reading the servicing tips and other info provided by PMM, Phil G4SPZ et al, I was able to refresh all the lettering, adjust the sensitivity and balance the movement. It now performs and looks like new - to the extent that I'm using it almost every day and my DMM is hardly getting a look in !

I'm now encouraged to have a go at restoring my 8 Mark 5 and have a couple of questions about parts, but I think a new thread will be more appropriate for that ....

Many thanks again.

Jerry
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Old 22nd Nov 2013, 11:56 pm   #1102
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Default Re: AVO Multimeter survey

Recent purchases are two Mark III '8's.

50652 1066 which I suspect has had something it didn't like shoved up it, no DC volts readings but everything else seems fine.

29888 1165 this one had a sticky pointer due to a couple of solder blobs in the coil housing and a difficult to zero /100 Ohms range. Cleaning contacts fixed this.

Andrew
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Old 27th Nov 2013, 10:23 pm   #1103
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Default Re: AVO Multimeter survey

Hello.

My name is Brian and I collect AVOs, it is good to be somewhere that understands.

Mine are mostly AVO8 MK7's which I still use most days at work as a commissioning engineer on high voltage transmission equipment. I have seven of these and they are used during ratio checks of transformers and also testing current transformers. I also have two 40 MK2's which have been used for many years as they have the 120 scale, very useful for CT polarity checks as the damping is not as severe as on the newer models. Also useful for saturation checks as the 120 scale means I do not have to swap ranges at the upper end of the test.

The two 40's actually came back from calibration with big red do not use stickers on them and when I asked why they said they had flashed over during the 2500 volt test. I did not even know they had been doing that test but apparently they had been passing OK every year for the last seven years. Opened the case, cleaned the tracking marks, left by a radiator over night and they passed again. Try that with a Fluke!
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Old 4th Dec 2013, 7:47 pm   #1104
Paul Adams
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Default Re: AVO Multimeter survey

Well go on say it, I know I said no more but who couldn’t resist this one.

I think from my others it’s a 36 Range Model, in need of some Terminal posts, as the original ones had sheared off, and had to be removed with the aid of a hacksaw and some heat as in the first photo.

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Apart from the above, the movement is solid, and the fuse is missing

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Anyway here’s the serial: 124-3306 which I think translates to December 1934.

Paul.
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Old 4th Dec 2013, 7:49 pm   #1105
Paul Adams
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Default Re: AVO Multimeter survey

Missed a photo... Click image for larger version

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Paul.
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Old 5th Dec 2013, 12:47 am   #1106
Phil G4SPZ
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Default Re: AVO Multimeter survey

Hi Paul,

That certainly looks like an early model. I have a 36-range Avo with a siezed movement, plus a painted scale plate and cracked front panel. I think you gave it to me! It has a fuse present, plus two (non-identical) terminals. You are welcome to have these bits if you think you will be able to make one good instrument out of two scrappers. Drop me a PM.
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Old 5th Dec 2013, 1:10 am   #1107
Paul Adams
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PM Sent.

Paul.
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Old 5th Dec 2013, 8:26 pm   #1108
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Default Re: AVO Multimeter survey

Paul,

Your serial number, 124-3306 would correspond to a 36-range Universal Avometer made in December 1934.

You can confirm the model type by checking that it has a 480V (AC) range. If this range is missing it would be the very rare 34-range Universal Avometer which began production in December 1933 and was replaced by the 36-range in June 1934. As far as I know, the model replacement was complete, i.e. 34-range production stopped immediately when the changeover took place. However, there seems to have been a surplus of instruction plates for the 34-range model which were used up on early 36-range meters; yours may have the older instruction plate.

My earliest 36-range Avometer is serial number 124-3337, so we know that at least 31 were made that month - probably quite a few more. Christmas day was a Tuesday in 1934 so I expect that the staff would have had that day off and possibly the Wednesday, so production would not be greatly disrupted. In Scotland however, I have been told that at that time, Christmas day was not a universal holiday. (Dour Presbyterian attitudes of the the 1560s saw no reason to allow celebrations and their effect lasted a long time - fortunately we're a little more enlightened now, at least most of the time). Mr. MacAdie was after all a Scot but he didn't take part in the everyday running of the company and would have enjoyed Post Office holidays, so let's hope the ACWEECO staff did have both days off.

PMM
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Old 5th Dec 2013, 8:57 pm   #1109
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Default Re: AVO Multimeter survey

Brianjd,

I missed your post for some reason.

You must be quite rare in having so many Model 8 Mark 7s. By the end of production, that would have been around £6500 worth!

A couple of years ago, I was asked to look at a Model 8 Mark 5 which was returned from "calibration" marked as "Unserviceable". The fault turned out to be a faulty, not blown, fuse in the test leads. Happily that meter lived to read another day, although I suspect that in may organisations it's fate would have been in a skip. It's good to know that you are willing, and able, to take the trouble to keep your Avometers working.

The Model 40 service manual is prepared as a supplement to the Model 8 Mark I & II service manual, so it may be assumed that the Model 8 flash test applies to the model 40. (Please see attachment). The specified flash test voltage is 6000V rms so the 2500V test is quite modest.

Presumably your Model 8 Mark 7s are also flash tested. I don't have service manual for the Mark 7 (I don't know if one was ever made available externally) but the Model 8 Mark V flash test is specified at 7000V rms.

In your line of work, these flash test voltages are quite justifiable, but I suspect few of us would otherwise be too concerned about them.

Do your model 40s have Bakelite or aluminium back cases? It would seem intuitive that the aluminium cased version would be more difficult to insulate to this standard as the insulation was very thin Bakelised fabric. This was also true of the much earlier Avometers and a 1936 Post Office Engineering assessment report of the 36-range Universal Avometer did conclude that the meter might be unsuitable for use at 1200V rms although no reason was given to justify this conclusion.

Would you like to contribute serial numbers to the survey?

PMM
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File Type: pdf 12.pdf (329.6 KB, 226 views)
File Type: pdf 18_pdfsam_Model 8 Mk V Service Manual Part 1.pdf (112.6 KB, 237 views)
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Old 9th Dec 2013, 7:12 pm   #1110
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Default Re: AVO Multimeter survey

I have a few more now, I can't remember which ones I have already submitted so here is the complete list:

Model 7 s/n 6412-A-748
Model 40 s/n 417599-1146
Model 40 MkII s/n 941617 40/12/75
Model8 MkI replacement meter
Model8 MkII s/n 142829-c-762
Model8 MkII s/n 105043-c-360
Model8 MkIII s/n 79168-468
Model8 MkIV s/n 52??3 84/4/71
Model8 MkV s/n 92447 8V/6/73
Model8 MkVl s/n 0005274FE 8VI 12/84
Test Set Multi Range No 1 High Sensitivity s/n 12195-8-71
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Old 18th Dec 2013, 6:51 pm   #1111
DoctorWu
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Default Re: AVO Multimeter survey

Just checked the scale plate of my workshop AVO.
It's a model 8 mark II, serial number 90179-C-459. It has a calibration sticker from May 1977 that indicates it was then being used by Smith Industries, Watford.

It also has an VC1 that I rescued from a skip!

I have another one in the "to be restored" box. I'll check the details and add it to the list.

John
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Old 20th Dec 2013, 4:54 pm   #1112
reactolite
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Default Re: AVO Multimeter survey

My AVO meter is the Heavy Duty and is still in it's light tan leather case with warranty card and a card advising ordering part numbers for spare leads also test certificate showing SERIAL No. 6564 Type HDS.
Hope this info will be of some use.

Last edited by reactolite; 20th Dec 2013 at 4:56 pm. Reason: Misspelling
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Old 23rd Dec 2013, 4:36 pm   #1113
DoctorWu
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Default Re: AVO Multimeter survey

Just looked out the second-best AVO. It's a Model 8 Mk III, S/N 12184.365

John.
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Old 28th Dec 2013, 7:31 pm   #1114
Mikey66
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Default Re: AVO Multimeter survey

Here's my recently acquired Avo 8 serial number
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Old 29th Dec 2013, 10:28 am   #1115
Pilotltd
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Default Re: AVO Multimeter survey

Mine says

Model 8. № 171800-C-366

Works fine except for setting zero on X100 where it jumps around the zero point.
No amount of contact cleaning or battery replacing wants to fix it.

I also have the original manual that came with it.

It says it's a Panclimatic Model 8x - what Mk would would it be?

Steve
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Old 29th Dec 2013, 4:35 pm   #1116
pmmunro
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Default Re: AVO Multimeter survey

Steve,

A 1966 Model 8 would be a MkIII; there were panclimatic versions of Mk I to III of the Model 8 and also screened panclimatic (8SX). I don't have catalogue information on corresponding variants of the Mark IV but I believe there was a Military version which would have been SX specification.

The Model 8 Mk V was designed to cover all requirements without any need for 8/9 S or SX versions.

PMM
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Old 30th Dec 2013, 2:44 am   #1117
Pilotltd
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Default Re: AVO Multimeter survey

The guy I bought it from reckons he bought it new in late 71 direct from Avo?

Does the 171 not mean Jan 71 in the serial 171800-C-366 ?

Steve
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Old 30th Dec 2013, 8:42 am   #1118
pmmunro
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Default Re: AVO Multimeter survey

Steve,

Some pictures would help. At this time, Avo serial numbers were fairly logical - the year and month of manufacture were in the format ssssss-mmYY.

A Model 8 made in 1971 would be a Mark IV which has a moulded thermoplastic back case with a detachable instruction plate held by a quarter-turn fastener giving access to the cell and battery.

PMM
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Old 30th Dec 2013, 8:54 pm   #1119
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Here are the pictures. Access to battery's via plate on top.
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Old 31st Dec 2013, 12:52 am   #1120
pmmunro
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Steve,

It's begining to look as though you may have a hybrid.

The serial number indicates a meter made in March 1966 but the instruction plate gives the company's address as Vauxhall Bridge Road, London. A new factory was opened in Dover in around April 1964 and although production ran simultaneously at both sites, I don't think this was for long. By mid-1966, the address in advertisements was given as Dover, so it could just be that meters were still made in London in March 1966 or instruction plates were still being used up after London production ended.

The Model 8 Mark III differs from the Mark II in having a fuse, in the battery box, added for the protection of the resistance ranges, thermistor compensation for the moving coil, a change of magnet material, usually distinguished by blue crackle paint, and component resistors rather than wound coils for the multipliers on the voltage ranges. On panclimatic versions, the earlier multipliers were resin encapsulated bobbin-wound wire coils; I'm not sure what was used on Mark III panclimatic meters. Some meters have an indication of the Mark on the small designation button on the front panel but yours is blank, so there's no help there. The rectifiers changed from Westinghouse copper oxide to germanium diodes, but I can't give an exact date for this and it may not have coincided with the change of Mark designation.

The battery cover on your meter is from either a Model 8 SX or a military Test Set High Resistance No 1 both of which had a steel screening can finished in hammer effect paint. However, it could be that this paint finish was also used for a commercial 8X because it has higher corrosion resistance than the standard black laquer.

Since the battery cover may not be the original which belonged with the case, it is also possible that the case, and hence the instruction plate, is not orignal either. Some repairers didn't seem to be too concerned to put the meter back in its own case. It is even possible that the movement is not on the original front panel.

If you are concerned to know more, some interior pictures will be needed. I don't know how familiar you are with these meters, but there are long pointed hexagonal-section contact posts for the battery connections; these are fixed to the small moulded plates for the resistance adjuster pots and these plates are very easily broken if there is any sideways force on the contact posts. (The usual guidance for avoiding dirt and dust apply of course).

PMM

PMM
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