G & E Bradley AC Calibrator

[Superscope]

Can anybody tell me anything about this Beasty?

Ok, I know it is an Ac Calibrator.

How would this have been used ?

Is it of any use to anybody these Days?



Ian

[Skywave]

It looks like it could be someone's idea of a signal generator. I think I can see a frequency range selection switch and a voltage level output set of controls, but without a few more photos taken as close-ups, difficult to be sure.
In photo 1, what's that box (half shown) on top of this item?
As for use, "signal generator" says enough!

Al. / Sept. 22nd.

[Bill]

It looks like an AC version of the Bradley 134 DC calibrator. The latter could supply a very accurate voltage , set on the switches up to 1000v (DC). Main use as I recall was for checking calibration of Avometers etc. Presumably , this one is to check AC ranges?

[Superscope]

Hi Bill,

That sounds very plausible, the Chap who owned it did used to
repair and Calibrate Avometers.

I am told it was still in use up until a couple of Months ago.

I haven't powered it up myself, at least not until I know what
I'm looking at.

G & E Bradley seemed to have been fairly big at one time, but I
can find no information at all about this Device.



Skywave,

Photos attached.

The thing on Top is a totally unrelated PSU.


Ian

[Radio Wrangler]

It does the neat trick that when you're calibrating a multimeter on say the 100v range, you dial up 100v on the calibrator and then either set the levep pot to show 0% on the calibrator's meter, so the multimeter shows what it will when hit with an exact 100v, OR you twiddle the level pot so the multimeter reads correctly, 100v and the meter on the calibrator shows how many percent the multimeter is off.

David

[ms660]

WME bill might still have a manual:

https://www.vintage-radio.net/forum/....php?p=1185610

Lawrence.

[Julesomega]

I scanned the manual a year or two ago: The complete document is a PDF of 11MB which should email ok or I can send individual pages, if you email me. It includes the 1254 tuned circuits plug-in

[Julesomega]

The Introduction pages will give you a better idea of the instrument
You will already know it's a monster of a beast, or vice versa, at 22kg

[Skywave]

Ian (Superscope): you have a P.M.

Al. / Sept. 22nd.

[Superscope]

Thanks Julian,

PM sent.

[Oldtestgear]

These AC calibrators are very heavy, valve based, dinosaurs. They are also capable of great stability over short periods & are accurate. I have had a copule of old Bradley calibrators pass through my hands over the years & all worked with minimal attention even after many years on inactivity in Plymouth Dockyard.

Not desperately useful with modern precision DMMs but still of some use.

Phil

[Superscope]

The Heavy bit I found out when I picked it up!

The Valve based Dinosaur bit I discovered when I open up the lid.

Then I discovered it probably hadn't been used in Years, contary to what I was lead to believe,
and Mice had clearly been Nesting in there at some point.

So there will be quite a bit of work cleaning this up, and I haven't decided yet
if I'm prepared to take this on.

I think some of the Top facing Boards will need to come out for cleaning which
will involve a fair amount of de-soldering.
The underside Boards are virtually Mint though, so there's hope.

Will have a read through the Manual Julian kindly sent me.

This was not the Plan though, when I picked this Stuff up!

But it would be very useful for Calibrating Avometers.
Trouble is, I just want to work on the Meters, not really have to work on the Test Equipment as well.

Ian