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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 1st Dec 2022, 8:01 pm   #1
pmmunro
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Default AVO Universal Measuring Bridge No. 1

I have one of these units which I have had for many years but I have not had an opportunity until now to make an assessment of it. First impressions are that it is very well constructed and that a great deal of thought has gone into its design. For these reasons it would be good to restore it to full working condition.

Thanks to the forum and its contributors I have been able to download the manual fron an old thread from 2010:

https://www.vintage-radio.net/forum/...ad.php?t=58775

The discussion in this thread seems to suggest that the 29 pages and diagram within this thread might not be all that was published. If there is more, it could possibly be servicing instructions and I would find this information useful if it exists. Can anyone help please?

From what I can gather, this measuring bridge was designed for use by UK armed forces as well as being sold commercially. On mine, the mains cable is brought in through a simple grommet, but I understand that the military units had a mains plug and socket of the same type as on the CT160 valve tester. Does anyone know what its military type number of the Measuring Bridge was please?

PMM
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Old 2nd Dec 2022, 8:14 pm   #2
Ed_Dinning
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Default Re: AVO Universal Measuring Bridge No. 1

Hi Peter, I have one of these, the commercial version I believe.
It is very well built and works well, but needed the slide wire cleaning often, hence I tend to use my TF2700.

It has the higher voltage cap test facility that the 2700 does not, but I'd be interested if the handbook gave details of measuring inductors with DC (another roundtuit for the 2700)

Ed
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Old 4th Dec 2022, 11:58 am   #3
ex 2 Base
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Default Re: AVO Universal Measuring Bridge No. 1

Hello Peter, I have an ex-military (REME) AVO test bridge, and it has mains lead which passes through the metal case, but no grommet. My meter is in a padded wooden box and on top it says AVO test equipment No5. The meter has already been registered on the AVO register. Someone sent me a copy of a 13-page restoration manual, if you would like a copy of what have, I can scan it and sent it to you via an an email. If you find more information on restoration of the test bridge, please let me know, and if my 6B8G turns out to be defective, do you know if they are readily available? Ted
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Old 5th Dec 2022, 5:52 pm   #4
2000 type
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Default Re: AVO Universal Measuring Bridge No. 1

I can't find any evidence that the British services used this AVO bridge. Unless someone comes up with an example with a service reference number on it of course.

For Component or "Universal" bridges they usually went to Wayne Kerr ( e.g.B521 / CT375, CT492 and B221 / CT530) or Marconi Instruments (e.g. TF936 / CT43, TF868, TF465, TF2700 and TF2701).

There are likely others, it's not always easy to cross-reference from the military descriptions.
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Old 5th Dec 2022, 8:16 pm   #5
pmmunro
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Default Re: AVO Universal Measuring Bridge No. 1

Thanks everyone for your interest.

It might have helped if I'd attached an image so that it's clear which unit I'm referring to as AVO's naming convention and lack of type numbers is a good formula for confusion.

Due to the file size limit here, the image quality is not great but should be enough to show the range of instruments to which this one belongs - it's the same range as the Type 378 signal generator (CT378A) and the Transistor Analyser (Inter Services Spec. K.114).

As the catalogue page shows, "This instrument meets the requirements of the U.K. Air Registration Board" but since that was a civil avaiation authority it doesn't necessarily follow that there was a military version although I thought another forum contributor had written that theirs was a Services version.

As Ed commentated above, it is made to a very high standard and price lists show it cost 3 times a contemporary Model 8 multimeter, so it does seem it might have had to meet an MOD specification.

PS - A higher quality image (Creative Commons licence) courtesy of the Science Museum

PMM
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Last edited by pmmunro; 5th Dec 2022 at 8:23 pm.
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Old 6th Dec 2022, 6:14 pm   #6
ex 2 Base
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Default Re: AVO Universal Measuring Bridge No. 1

Sorry Peter, I was referring to an entirely different test bridge. Ted
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Old 7th Dec 2022, 7:23 am   #7
pmmunro
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Default Re: AVO Universal Measuring Bridge No. 1

No need to apologise Ted, I should have posted a picture to avoid confusion.


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