Fluke 725a Kelvin Varley Voltage Divider

[rigrunner]

Does anyone have a service manual and/or schematics for one of these?

Date code inside the lid is November 1967. It's a few weeks younger than me

[veedub565]

10yrs older than me!

I've got one of these, along with a 750A, 723A, 752A, 845AB. I salvaged them from a dumpster (with permission). It seemed sacrilegious to just dump this nicely engineered stuff in the bin. I don't really need any of it, but I wanted to save it, and teach myself how to use it, purely out of interest. I find it quite aesthetically pleasing too, it's a nice thing to look at. Oh dear, I better get over to the TEA thread

I'm afraid I don't have a manual, but if I find one I'll let you know.

[tggzzz]

The theory of KVDs is simple and we'll described in many places. The corresponding schematics are easily derived; just about the only variable is the input resistance.

As for servicing, what is needed? Basically I'd trust a KVD more than most devices.

[rigrunner]

10yrs older than me!

I've got one of these, along with a 750A, 723A, 752A, 845AB. I salvaged them from a dumpster (with permission). It seemed sacrilegious to just dump this nicely engineered stuff in the bin. I don't really need any of it, but I wanted to save it, and teach myself how to use it, purely out of interest. I find it quite aesthetically pleasing too, it's a nice thing to look at. Oh dear, I better get over to the TEA thread

You have a dumpster of worth sir

I'm afraid I don't have a manual, but if I find one I'll let you know.

Likewise

The theory of KVDs is simple and we'll described in many places. The corresponding schematics are easily derived;

Indeed, but anyone who goes around reversing every piece of equipment before trying to obtain schematics/manuals has way too much time on their hands.

just about the only variable is the input resistance.

For this particular item it's 440K at the 1.1 input and 400K at the 1.0 input - both +/- 0.02%

As for servicing, what is needed? Basically I'd trust a KVD more than most devices.

The unknown provenance, age, all those things to twiddle and the "Do not use" tag give me reason not to trust just yet 

[tggzzz]

The theory of KVDs is simple and we'll described in many places. The corresponding schematics are easily derived;

Indeed, but anyone who goes around reversing every piece of equipment before trying to obtain schematics/manuals has way too much time on their hands.

Have you looked at the schematic for a KVD? It is simple!

just about the only variable is the input resistance.

For this particular item it's 440K at the 1.1 input and 400K at the 1.0 input - both +/- 0.02%

As for servicing, what is needed? Basically I'd trust a KVD more than most devices.

The unknown provenance, age, all those things to twiddle and the "Do not use" tag give me reason not to trust just yet 

If you are going to twiddle, you will need 7 digit equipment. If you don't have that, don't twiddle.

[rigrunner]

If you are going to twiddle, you will need 7 digit equipment. If you don't have that, don't twiddle.

I meant that others may have twiddled in the time since it left service and now. Sorry for the lack of clarity.
I'm good with 7 digits.

[veedub565]

There's some info on the 720A here https://xdevs.com/fix/f720a/

[tggzzz]

If you are going to twiddle, you will need 7 digit equipment. If you don't have that, don't twiddle.

I meant that others may have twiddled in the time since it left service and now. Sorry for the lack of clarity.
I'm good with 7 digits.

If by that you mean you have 7 digit equipment, then out of curiosity, what is it?

[rigrunner]

There's some info on the 720A here https://xdevs.com/fix/f720a/

That turned up in my earlier googling. It's going to be very similar.

I enquired of Fluke about the 725a and they replied "After some digging around and looking through some old catalogues.
The 725A Kelvin Varley Voltage Divider was last produced 1967. As a result the manual is no longer available from Fluke."

If by that you mean you have 7 digit equipment, then out of curiosity, what is it?

A few 8.5 digit meters. A couple of Datrons, a couple of Solartrons and a nearly useful Transmille.