UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio 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 20th Nov 2019, 12:30 am   #21
Superscope
Pentode
 
Join Date: May 2017
Location: St Austell, Cornwall, UK.
Posts: 240
Default Re: AVO Model 7 Restoration

PMM,

Thanks, that's useful to know.

Was the Model 7 launched with the Compensator do you know?
or did it come some time later?

Did any other Models have one?


Ian
Superscope is offline   Reply With Quote
Old 20th Nov 2019, 3:50 pm   #22
Tim
Nonode
 
Tim's Avatar
 
Join Date: Jan 2003
Location: Bradford on Avon, Wiltshire, UK.
Posts: 2,785
Default Re: AVO Model 7 Restoration

Quote:
Originally Posted by TonyDuell View Post
Silly suggestion (?) Could you not shunt a DMM (normally 10M input resistance) with a suitable resistor to make it the equivalent of a 1000 ohms per volt meter? If, say you would have used a 100V range on the AVO 7, connect a 100k resistor in parallel with the DMM (it will be near enough for this sort of measurement I think)
Yes probably, but then I wouldn’t have the pleasure of using( and looking at) an AVO7.
__________________
"Nothing is as dangerous as being too modern;one is apt to grow old fashioned quite suddenly."
Tim is offline   Reply With Quote
Old 20th Nov 2019, 5:34 pm   #23
Tim
Nonode
 
Tim's Avatar
 
Join Date: Jan 2003
Location: Bradford on Avon, Wiltshire, UK.
Posts: 2,785
Smile Re: AVO Model 7 Restoration

Thatís what I told my wife, as to why I needed ANOTHER meter. Please donít give me away!
__________________
"Nothing is as dangerous as being too modern;one is apt to grow old fashioned quite suddenly."
Tim is offline   Reply With Quote
Old 21st Nov 2019, 2:34 pm   #24
pmmunro
Octode
 
Join Date: Jul 2004
Location: Dundee, UK.
Posts: 1,263
Default Re: AVO Model 7 Restoration

Ian,

Temperature compensation was advertised as one of the characteristics of the Model 7 in the advertisements which announced its introduction so it seems certain that it was used from the beginning until the movement design changed.

It was patented, GB 476682, application date 12th May 1936, Complete Specification accepted 13th December 1937. The Model 7 was introduced in August 1936.

The complete specification states:

"The chief object of the invention is to provide means for compensating for changes in ambient temperature and to provide some correction for overheating due to misuse of the meter, whereby the accuracy of the reading may be retained within the limits of temperature compensation possible with the device".

I have never seen another Avo instrument which uses this form of compensator. This could be because the Model 7 was the most sensitive "full-size" Avometer until the Model HR was introduced around 1948, but the HR had a block magnet movement which perhaps did not need temperature compensation. The first HR which I obtained did however have temperature compensation using a thermistor. It had been fitted with a Model 8 Mk III movement in what seemed to have been a factory repair.

PMM
pmmunro is online now   Reply With Quote
Old 29th Nov 2019, 9:00 am   #25
Tim
Nonode
 
Tim's Avatar
 
Join Date: Jan 2003
Location: Bradford on Avon, Wiltshire, UK.
Posts: 2,785
Default Re: AVO Model 7 Restoration

Hi Ian. Not sure about T. C thingy.
Prompted by this thread I had another look at my meter, which might even be 1951.
The blurb on the back of the meter mentions the fact the battery is required to bias the AC rectifier(which I didnít know until I read it here) but as far as I remember no mention of any temperature compensation.
I really must take some photos.
__________________
"Nothing is as dangerous as being too modern;one is apt to grow old fashioned quite suddenly."
Tim is offline   Reply With Quote
Reply

Thread Tools



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


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 - 2019, vBulletin Solutions, Inc.
Copyright ©2002 - 2019, Paul Stenning.