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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 25th Jan 2016, 9:43 pm   #1321
Pmark34
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Default Re: AVO Multimeter survey

latest in the collection a Model 12. No.1?(9 maybe)26-1166 so Nov 66 I think. fully working with some accessories.The leather case is all there but a bit tatty. the meter has some minor scuffs and a small crack in one corner but otherwise in good condition. I belive these had a 90A & or 900A shunts.sadly missing (if anyone has one PM me please) Looks like it was serviced by Farnells wertherby.The seal on one of the back screws had already gone so have had a look in side & all looks good.
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Old 26th Jan 2016, 9:11 am   #1322
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Default Re: AVO Multimeter survey

Pmark34,

You are correct in you interpretation of the date of your Model 12. This meter was designed in response to the need for an instrument suitable for use with alternator systems then coming into use to replace dynamos. It is likely that Lucas cooperated in its design.

The 90A and 900A shunts were optional and could be specified for supply with a new meter or as separate accessories.

It was a very useful instrument; I bought one new and used it for its intended purpose for several years.

PMM
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Old 2nd Feb 2016, 11:29 am   #1323
Phil G4SPZ
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Default Re: AVO Multimeter survey

Kindly donated by a Forum member for the cost of postage, Avo Model 8 Mk III serial number 19314-665. In poorly condition with a sticking movement, a cracked case, missing screws and some very dirty insides, but it's in good hands in the Avo ITU, and now that it has entered preservation I'm confident that it will be well again in the near future. No need for grapes, flowers or get-well cards though, please!
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Old 1st Mar 2016, 11:53 am   #1324
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Another one to add to the ever growing colection .Brought from a auto jumble at the weekend for £20. A Universal Avo 8 mk 2 no,148108.c.1162 (so Nov 1962) not sure what the C stands for.In good condishion fully working with a good set of AVO leads,also nice to find when i got it home it has got a VC1 voltage converter in it.
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Old 1st Mar 2016, 12:17 pm   #1325
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Default Re: AVO Multimeter survey

You did VERY well to bag a VC1. They tend to go for about £50 alone !

One downside with the VC1, in my opinion, is that it's "on" all the time. Admittedly, it's a very low current circuit but it's still an extra drain on the 1.5V cell. Please do keep an eye on it and aim to replace the cell regularly - say every 12 months or sooner. If you're not going to use the meter much, I'd definitely recommend removing any cells or batteries to avoid leakage.

Jerry
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Old 21st Mar 2016, 4:48 pm   #1326
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Default Re: AVO Multimeter survey

Found a Model 7 in an antiques centre this morning, so had to buy it. It's in generally good condition, apart from a couple of chips in the casing, and the dial markings and glass are both very clear. A new set of leads will definitely be required though, as the originals have decomposed badly. The meter comes complete with a good case.

Haven't had the chance to play around with it yet, but would like to get it 'on the system' - serial number is 86559-A-261. Anyone any idea of when it might have been made?
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Old 21st Mar 2016, 5:02 pm   #1327
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Oldmoley1,

Your Model 7 was made in February 1961 as indicated by the last three characters of the serial number.

PMM.
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Old 21st Mar 2016, 10:14 pm   #1328
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Many thanks. God, I feel old - I was four at the time!
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Old 23rd Mar 2016, 4:07 pm   #1329
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Hello! It the first time I write on this forum. I am a Avo's collector at least 10years, and I read with great interest by the same number. I just purchased a DC AVOMETER mod.2 13range from EBay Germany (Berlin). The instrument (N.3284) built in Rochester Row London was a special export version (instruction plaque in German with the importer's adress in Berlin). Whereas it has probably spent the war and bombing in Berlin, was in fair condition. Clean outside and inside. The scale plate had detachments of paint and had been badly restored. Inside the rheostat did not touch with the last third, two resistors had a Thermal injury (but the value is unchanged). The battery case was changed to a modern cell. The selector had two false contacts. I restored the scale plate with an almost accettable result, repaired the rheostat which was bent to one side, reset the contacts of the shitch,cleaned and lubrificated everything possible, repainted the red pointer For the age that is quite accurate even if the movement has some uncertainty. The question is. the construction year is 1929 or 1930? Many thanks. Palmerino (Rome Italy)
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Old 23rd Mar 2016, 9:37 pm   #1330
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Palmerino

It's good to hear from you; thank you very much for getting in touch with the forum and for the information about your meter.

It is a rare and interesting model. Even in the UK 13-range Avometers made in Rochester Row are very rare, but those with a German instruction plate are probably even rarer. I have certainly never heard of another although a German patent, DE405863 was granted on the 11th November 1924, so it is not entirely surprising that some were sold in Germany.

I would certainly agree that it is a fortunate survivor having presumably gone through the Second World War in Germany. It is not unusual for Avometers of this age to have flaking paint on the scale plate. The paint seems to have been applied directly to the plating, which I assume was nickel plating - for the mirror arc - and its very difficult to get paint to stick to a polished surface like this.

It is also quite rare to find a pre-1939 Avometer in which the highest restance multiplier resistor is undamaged. The large number of turns of fine wire are very easily damaged and even just rubbing them on a bench top might be enough to cause a break.

The switch spindles would certainly benefit from lubrication; the spindles can get quite stiff but the moving coil pivots should be left unlubricated.

These meters were made in Rochester Row between 1927 to around 1930 when production was moved to Douglas Street; the two addresses are very close together. I don't have any way of giving a more exact date of manufacture as the serial number does not include a date code but 3284 is quite a high serial number for Rochester Row so it is possibly from around 1930.

If you would be good enough to send some photographs, these would be of interest as would any information you would like to give about the rest of your collection. I have seen a few Avometers from Italy advertised on eBay, usually at quite high prices by UK standards. I would be interested to know how common Avometers were in your country.

PMM
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Old 26th Mar 2016, 12:00 am   #1331
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I gives me a great thrill respond to PMMurdo which I consider one of my Masters (I fondly recall even SPCH). Unfortunately I can not upload photos. I have to study more! Happy Easier, ciao Palmerino.
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Old 26th Mar 2016, 1:02 am   #1332
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This should help: https://www.vintage-radio.net/forum/...ad.php?t=77650
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Old 26th Mar 2016, 6:53 pm   #1333
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Two more to add to the collection. Avos no,17 & 18 in my collection, firstly a Universal Avo 8 mk 3, fully working with good leads,NO.19267.665 ,Secondly a model D No,20328.545 in good condition seems to work fine on the voltage scales but not on the ohms scales, on 1000 ohms (With center knob set at K2) it reads over FSD and will not ajust, but on the 10,000 ohms scale it will not read at all, battery seems ok & the P & R ajusters seem to make contact ok, all be it a little stiff.Have also noticed inside it two "moden" looking resisters in parallel to each other(see pic,hope its clear enough) think they are the same value as each other. Are they origonal or not? Also the back plate is quite badly scufed so if any one has a pdf of the back of a Model D (or any user info) I would greatly appreciate a copy of any info.Thanks
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Old 26th Mar 2016, 7:13 pm   #1334
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Pmark34,

It seems you could do with a circuit diagram for your Type D; send me an email address by private message and I will get one to you.

I had a batch of Type D instruction plates reproduced from a new unused one which was given to me. These are indistinguishable, at least to my eye, from the original. If you want one, £5 plus postage would cover my costs. I could probably find some of the right size of copper rivets to go with it. (The usual aluminium rivets used for instruction plates seem to have been in short supply during the Second World War).

PMM
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Old 26th Mar 2016, 8:33 pm   #1335
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Those modern resistors have been used to repair the small resistance winding(s) associated with the ohms ranges, which are on the small separate paxolin board. I have done similar repairs myself. The values are quite critical; 186 ohms, 15 ohms and 1.06 ohms, adjusted on test. It sounds like the 186 ohm winding may be open-circuit since the 10,000 ohm range doesn't work at all.

If the 1.06 ohm resistance wire has been replaced, it's possible that the repairer has tried to make up the required value using two resistors in parallel. This resistance acts as a shunt across the movement on the 1,000 ohms ranges, so if it's too high the movement will exceed FSD even with the 'P' knob fully clockwise. Before you start though, ensure that the contacts of the associated leaf switch are absolutely clean. Then you could in fact try adding another fixed resistor across the two new ones; start with 22 ohms and work downwards.

The general method I use in such cases is to start with (say) a 1.2 ohm fixed resistor and connect a 100 ohm pot across it. Connect the battery, short the instrument terminals together, set the 'P' knob to fully-anticlockwise and adjust the temporary 100 ohm pot until the pointer reads ~10% below FSD. This should then enable you to set FSD using the 'P' knob, as the battery ages. Now measure the resistance of the parallel combination of the 1.2 ohm resistor and the 100 ohm pot, and try to obtain or make up a single fixed resistance equal to this value.

This process is a bit trial-and-error but it has never failed. Short, low-resistance connections are essential. Clearly, using resistance wire would be more appropriate but not easily accomplished in practice. Equally, measuring such low resistances isn't easy but if you have access to another Model D, the resistance scale can be read to less than half an ohm.

Good luck!
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Old 26th Mar 2016, 10:20 pm   #1336
Pmark34
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Phil
Thanks for your reply, I will have a go at the method you suggest,with the information for yourself & from PMM hopfully I will be able to get it back to full working order.will post how I get on.
thank you both
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Old 26th Mar 2016, 10:40 pm   #1337
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Quote:
Originally Posted by Phil G4SPZ View Post
...if it's too high the movement will exceed FSD even with the 'P' knob fully clockwise...
Typo. Sorry! That should read "...even with the 'P' knob fully anti-clockwise..."
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Old 31st Mar 2016, 11:21 am   #1338
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Hi; I send you some Avo 13range photos before resturation and the current one. Ciao Palmerino.
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Old 31st Mar 2016, 12:24 pm   #1339
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Hi, as for the rest of my collection I should prepare a detailed list. The first (fatal meeting) was a Avo7 no.54721.A-355 given my friend who worked for the Italian Army full probes and a brown bag made by Army saddlery. Later I sold me a disused army multimeter. A Samar M.V.1 and that almost a carbon copy of Avo7 but built in Milan, this also with the green military leather bag. The next three Avo I bought them from a surplus store in Rome (expensive). Others (20?) from Italy, Germany, France, Portugal and England (especially) Ebay. So I am a sufferer of Avo! Following your advice I built a wooden box with a glass window to balancing test the movements, a tool to test the cardinal points of the movements according to the digram of the technical manual of Avo5, two screwdrivers ont inductive. I have became quite skilled at balancing the movements but if they have suffered harm I surrender. About the 13range, it is interesting to note that the+ position of the selector tool indicates the charging status of the internal battery. I did not understand the rheostat function in series ammeter (charging limiter accumulators?). It is actually very difficult to paint directly on the chrome plate but before using as primer White corrector pen is easier. Ciao Palmerino.
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Old 1st Apr 2016, 9:04 pm   #1340
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Default Re: AVO Multimeter survey

I have two model 7 avometers from 1948:
4259-A-348 in black aluminium case
6412-A-748 in grey aluminium case
Apart from the casings the earlier one has some spool wound resistors rather than the more usual wound ones. Was this a short lived experiment I wonder?
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