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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 16th Oct 2020, 4:13 pm   #1
Nanozeugma
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Default AVO Test Bridge - a curiosity...

Hi.
I've acquired one of these and propose to restore it.
It appears to be in original condition and not "got at."
The markings on the meter movement date the unit to November 1947.
Familiarising myself with the circuit and construction, I came across this...

At the base of the unit there are four terminals. Two are marked with the chassis symbol. Attached to both of these (one each) - apart from other things - are two flat wirewound resistances, each is about 100 ohms.

Now the odd bit...

The other end of each resistance goes nowhere.
So far as I can tell, they don't appear on the circuit diagram.
Most, if not all other interconnections are marked with a dab of green paint.
The unconnected ends of these two resistances are not and bear no sign of EVER having been connected to anything.

I've no idea why they're there. Anyone else got a clue?
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Old 17th Oct 2020, 11:46 am   #2
The Philpott
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Default Re: AVO Test Bridge - a curiosity...

It seems to me that in the late 'forties there were a lot of changes in design going on at ACWEECO, and a lot of small variances in the production line. I am not surprised to encounter a vestigial component in an instrument from this period, tacked on and doing nothing! A slightly modified version of the instrument may have been in parallel production which did make use of these resistances- but beyond that i haven't got a scooby..

Dave
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Old 17th Oct 2020, 1:08 pm   #3
TowerRadio
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Default Re: AVO Test Bridge - a curiosity...

I wonder if they were for alignment when the unit was built and somehow got forgotten when the case was finally put on.Les
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