UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Test Gear and Workshop Equipment

Notices

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

Reply
 
Thread Tools
Old 13th Jul 2019, 11:46 am   #2201
micheal
Pentode
 
Join Date: Mar 2007
Location: Croydon, London, UK.
Posts: 111
Default Re: AVO Multimeter survey

I think the strengthening skirt was added because the cell was prised out with a screw driver and the thin case could not stand the strain and broke.

Early case's had 6v,120v and 300v markings where the later versions had 6v,60v and 300v. and a thicker overall case, so probably a new moulding.

Mike.
micheal is offline   Reply With Quote
Old 15th Jul 2019, 8:01 am   #2202
AndyGilham
Pentode
 
Join Date: Oct 2016
Location: Dover, Kent, UK.
Posts: 237
Default Re: AVO Multimeter survey

Quote:
Originally Posted by AndyGilham View Post
A new ebay purchase
Avometer Model D (10S/10610) - Serial Number 19110-345 (March 1945)

Looks to have a missing Terminal Knob, so i will 3D print a replacement. Other than that, it looks in good condition. I will upload some photographs once its delivered.

Regards
Andy

As promised, please find attached some photos of the Moel D.
The instrument front panel is missing a terminal, but generally its in good shape.
The first thing i noticed internally was the resistors. It seems at some point one of the current shunts on the shunt board had burnt out (low current, 0.015A??), and so replaced by 2 series resistors.

Additionally, one of the shunts on the resistance board has been wrapped in a solder resist tape. I assume this was due to the windings becoming loose.

Andy
Attached Thumbnails
Click image for larger version

Name:	IMG_3650.jpg
Views:	120
Size:	50.7 KB
ID:	186712   Click image for larger version

Name:	IMG_3653.jpg
Views:	143
Size:	49.7 KB
ID:	186713   Click image for larger version

Name:	IMG_3662.jpg
Views:	130
Size:	78.8 KB
ID:	186714   Click image for larger version

Name:	IMG_3661.jpg
Views:	138
Size:	55.9 KB
ID:	186715   Click image for larger version

Name:	IMG_3657.jpg
Views:	129
Size:	83.1 KB
ID:	186716  

AndyGilham is offline   Reply With Quote
Old 15th Jul 2019, 11:17 am   #2203
The Philpott
Dekatron
 
The Philpott's Avatar
 
Join Date: Aug 2016
Location: Colchester, Essex, UK.
Posts: 4,147
Default Re: AVO Multimeter survey

Hi Andy, the translucent tape is often in evidence on the 150v winding pictured- not sure why.

I think that the scorched lower left winding replaced by resistors is probably the 7.5vAC winding. That's a typical place for the lowest ACV range to be.

Dave
The Philpott is offline   Reply With Quote
Old 15th Jul 2019, 11:24 am   #2204
The Philpott
Dekatron
 
The Philpott's Avatar
 
Join Date: Aug 2016
Location: Colchester, Essex, UK.
Posts: 4,147
Default Re: AVO Multimeter survey

Ouch- just noticed the safety cut-out's contact leg has been arc damaged in photo 4- the big carbon contacts are aligned to open after the inboard gold-silver contacts, which (you hope) protects the latter.

Dave
The Philpott is offline   Reply With Quote
Old 15th Jul 2019, 5:50 pm   #2205
The Philpott
Dekatron
 
The Philpott's Avatar
 
Join Date: Aug 2016
Location: Colchester, Essex, UK.
Posts: 4,147
Default Re: AVO Multimeter survey

Model D- I can confirm that the burned out winding in pic 4 should be around 283 ohms..So the repairer did their sums right, even if they did rush it.

Dave
The Philpott is offline   Reply With Quote
Old 15th Jul 2019, 10:50 pm   #2206
AndyGilham
Pentode
 
Join Date: Oct 2016
Location: Dover, Kent, UK.
Posts: 237
Default Re: AVO Multimeter survey

Thanks for the observation and the update on the resistors. It’s a nice assembly, but does not look as robust as the model 7... which is strange, being a ministry variant
Andy
AndyGilham is offline   Reply With Quote
Old 16th Jul 2019, 8:58 am   #2207
Barnmead
Pentode
 
Barnmead's Avatar
 
Join Date: Dec 2002
Location: Norfolk, UK.
Posts: 168
Default Re: AVO Multimeter survey

my model D from August 1945 has a wire wound resistor on a glass tube rather than the pink ones.
Attached Thumbnails
Click image for larger version

Name:	modeldb.jpg
Views:	92
Size:	57.9 KB
ID:	186775  
__________________
Richard
Barnmead is offline   Reply With Quote
Old 16th Jul 2019, 12:41 pm   #2208
AndyGilham
Pentode
 
Join Date: Oct 2016
Location: Dover, Kent, UK.
Posts: 237
Default Re: AVO Multimeter survey

Richard,
I do wonder if mine had been modified, since the resistors are supported either end by a very flimsy board and the entire assembly is just held in place by the connecting wires.
A very weak assembly.

Andy
AndyGilham is offline   Reply With Quote
Old 16th Jul 2019, 3:23 pm   #2209
The Philpott
Dekatron
 
The Philpott's Avatar
 
Join Date: Aug 2016
Location: Colchester, Essex, UK.
Posts: 4,147
Default Re: AVO Multimeter survey

Good point, i hadn't spotted that- it is unlike the (late) '300v/750v' resistor packs i have seen, which consist of pairs of similar resistors either side of a much thicker paxolin board, (the connecting wires go through the board) and the whole thing has a brass bracket attached which enables it to be retro-fitted to any Model D using the fixing holes already present in the meter. What you have there may be an intermediate arrangement before the better ones were introduced. I think i recall that your meter is one of those that went back to the factory for a refurb indicated by the ACW mark on the scale plate..? The internals may have been changed then.

If you wanted the interior to look more period correct for year 1944/45 like Richard's (but NOT work on 300v/750 ranges) i have an open circuit glass tube type resistor somewhere that i have no use for.

Dave
The Philpott is offline   Reply With Quote
Old 16th Jul 2019, 6:53 pm   #2210
The Philpott
Dekatron
 
The Philpott's Avatar
 
Join Date: Aug 2016
Location: Colchester, Essex, UK.
Posts: 4,147
Default Re: AVO Multimeter survey

Here is the later high voltage resistor pack for the Model D, the brass mounting frame can be seen below it. Perhaps the one Andy has was one that somebody prototyped and the factory then improved on.

The second picture is a side view of an early Model 7- the only thing which doesn't look too robust is the wallace & gromit style temperature compensator- but it can actually be seen to work when you breathe on it!

Dave
Attached Thumbnails
Click image for larger version

Name:	DSC00302.JPG
Views:	106
Size:	135.8 KB
ID:	186807   Click image for larger version

Name:	DSC00312.JPG
Views:	102
Size:	130.3 KB
ID:	186808  
The Philpott is offline   Reply With Quote
Old 17th Jul 2019, 7:16 pm   #2211
AndyGilham
Pentode
 
Join Date: Oct 2016
Location: Dover, Kent, UK.
Posts: 237
Default Re: AVO Multimeter survey

I think this where my opinion of it not being robust stems from, this floating resistor arrangement. It just moves about within the recess.
It's always intriguing seeing these small variations in build! I am currently up to 9 variants of the model 7 (mark 1) resistance board..!
Think I'll leave it as it is...... Seen another model D for sale with glass tube!

Andy
AndyGilham is offline   Reply With Quote
Old 18th Jul 2019, 3:42 pm   #2212
The Philpott
Dekatron
 
The Philpott's Avatar
 
Join Date: Aug 2016
Location: Colchester, Essex, UK.
Posts: 4,147
Default Re: AVO Multimeter survey

Andy, i couldn't find the Model D glass tube i thought i had (on account of the fact it never existed..) but have sent you one from a Model 40 series for academic interest. Have a look at the thickness of the wire where it has pulled away from the tube- it is 1 thousandth of an inch thick, (25 micrometres)- a human hair is 3 thou. They managed to make these things to a resistance tolerance of around 0.2-0.3%...good even by modern standards.

When they made the slab and bobbin type windings they were always up against capacitance and inductance, hence the odd (usually patented or pat.pending) ways they wound them. I had one small bobbin that showed 12kohms then 14kohms when the polarity of the DMM leads was reversed- although i think this may have been down to the effects of internal corrosion. A resistor that dreamed it was a diode!

Dave
The Philpott is offline   Reply With Quote
Old 18th Jul 2019, 7:13 pm   #2213
pmmunro
Octode
 
Join Date: Jul 2004
Location: Dundee, UK.
Posts: 1,817
Default Re: AVO Multimeter survey

The glass tube form of resistor was the subject of two Patents assigned to Harold Edward Bayliss both applied for on March the 9th 1942 and accepted on the 17th December 1943. This would set the date at which these components could have been intriduced commercially.

The first patent concerns embedding the resistance medium in a coating on the tube as the resistor is wound to improve the mechanical stability of the wire. The second concerns the use of pressed out tabs in the clamp bands to provide an attachment point for the winding.

H E Bayliss took out these patents in his own name but later also had joint patents for winding machine accessories with ACWEECO, so may have been an employee of the company, at least at some period. He seems to have been a specialist in detail improvements in resistor manufacture.

In my experience, it is very rare to find a glass tube resistor of this type which is not open circuit, possibly due to stresses on the extremely fine wire used. In the long term, I do not think this type of resistor could be considered a success.

Concerning Andy's comments about the construction of the Type 'D' Avometer, I think it would be fair to think of those produced during the middle war years as having "Utility" construction due to shortages of specialist materials, such as the contact material for the cut-out. I don't think this is true of the corresponding Admiralty Pattern 47A & 48A; perhaps the Admiralty was less willing to take a pragmatic view than the Air Ministry.

PMM
pmmunro is offline   Reply With Quote
Old 19th Jul 2019, 6:50 pm   #2214
The Philpott
Dekatron
 
The Philpott's Avatar
 
Join Date: Aug 2016
Location: Colchester, Essex, UK.
Posts: 4,147
Default Re: AVO Multimeter survey

I think an additional problem with the (glass tube) resistors is that there wasn't a durable way of fixing the clamp bands to the glass.

Remarkably 4 of the 6 which i have are serviceable...at the time of writing.
Dave
The Philpott is offline   Reply With Quote
Old 25th Jul 2019, 5:14 pm   #2215
Sinewave
Octode
 
Sinewave's Avatar
 
Join Date: May 2016
Location: Oxfordshire/Bucks borders, UK.
Posts: 1,604
Default Re: AVO Multimeter survey

Two lovely goodies have come my way very recently.

First, something I've wanted for a very long time is the Power Factor and Wattage unit made to connect to the PF sockets of the Model 7 and 40. It's complete with the leads. I've just yet to try and see if it's working. There's not much them really in circuitry, so it should work. No serial number on this unit that I can see.

Also, with a very warm welcome indeed, I introduce into my collection a 20 range Avometer, other wise known as the Model 3. Serial No.13-928.
__________________
Avometer, vintage Fluke and Marconi collector. Also interested in vintage Yaesu and KW.
Sinewave is offline   Reply With Quote
Old 25th Jul 2019, 5:18 pm   #2216
Phil G4SPZ
Dekatron
 
Phil G4SPZ's Avatar
 
Join Date: Apr 2005
Location: Bewdley, Worcestershire, UK.
Posts: 4,756
Default Re: AVO Multimeter survey

Nice!

I thought that the PF & Wattage Units were made in different models for the Model 40 and Model 7? I have the Model 7 variant.
__________________
Phil

Optimist [n]: One who is not in possession of the full facts
Phil G4SPZ is offline   Reply With Quote
Old 25th Jul 2019, 5:30 pm   #2217
Sinewave
Octode
 
Sinewave's Avatar
 
Join Date: May 2016
Location: Oxfordshire/Bucks borders, UK.
Posts: 1,604
Default Re: AVO Multimeter survey

Yes, you're quite right. Mine does indeed say it's for a Model 7.

Now, this means there's another one I need to collect!

I assume the difference then is the range to FSD.
__________________
Avometer, vintage Fluke and Marconi collector. Also interested in vintage Yaesu and KW.
Sinewave is offline   Reply With Quote
Old 25th Jul 2019, 5:30 pm   #2218
Pamphonica
Nonode
 
Pamphonica's Avatar
 
Join Date: Mar 2008
Location: Virginia Water, Surrey, UK.
Posts: 2,904
Default Re: AVO Multimeter survey

Quote:
Originally Posted by Sinewave View Post
Two lovely goodies have come my way very recently.

First, something I've wanted for a very long time is the Power Factor and Wattage unit made to connect to the PF sockets of the Model 7 and 40. It's complete with the leads. I've just yet to try and see if it's working. There's not much them really in circuitry, so it should work. No serial number on this unit that I can see.

Also, with a very warm welcome indeed, I introduce into my collection a 20 range Avometer, other wise known as the Model 3. Serial No.13-928.

Nice job. I finally found one of those PF adapters (Model 7 version) for a tenner at a rally a few months ago.


And of course big congrats on bagging a Model 3. I know you have been waiting a while for an early Avo. Where did it come from in the end?


-Jeremy
__________________
Jeremy, G8MLK, BVWTVM Friend, VMARS, BVWS Secretary.
www.pamphonic.co.uk www.bttt.org.uk
Pamphonica is offline   Reply With Quote
Old 25th Jul 2019, 10:14 pm   #2219
Sinewave
Octode
 
Sinewave's Avatar
 
Join Date: May 2016
Location: Oxfordshire/Bucks borders, UK.
Posts: 1,604
Default Re: AVO Multimeter survey

Was just in the right place at the right time. Still a few more to go!
__________________
Avometer, vintage Fluke and Marconi collector. Also interested in vintage Yaesu and KW.
Sinewave is offline   Reply With Quote
Old 30th Jul 2019, 6:30 pm   #2220
AndyGilham
Pentode
 
Join Date: Oct 2016
Location: Dover, Kent, UK.
Posts: 237
Default Re: AVO Multimeter survey

I've only gone and got myself an EA113, serial number 6908, and yes, it's the black moulding version.
I got this for £40 from a gent who's late father purchased it brand new.

Andy
Attached Thumbnails
Click image for larger version

Name:	image.jpg
Views:	109
Size:	65.9 KB
ID:	187591  
AndyGilham is offline   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 2:10 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.