Fluke 725a Kelvin Varley Voltage Divider - Page 1
Forum section: electronics / general

author: rigrunner
author_rank: Frequent Contributor
timestamp: November 20, 2021, 03:30:09 am
content: 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

author: veedub565
author_rank: Frequent Contributor
timestamp: November 21, 2021, 09:19:31 pm
content: 10yrsolderthan 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 threadI'm afraid I don't have a manual, but if I find one I'll let you know.

author: tggzzz
author_rank: Super Contributor
timestamp: November 21, 2021, 10:52:30 pm
content: 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 isneeded? Basically I'd trust a KVD more than most devices.

author: rigrunner
author_rank: Frequent Contributor
timestamp: November 22, 2021, 12:26:45 am
content: Quote from: veedub565 on November 21, 2021, 09:19:31 pmYou have a dumpster of worth sirQuote from: veedub565 on November 21, 2021, 09:19:31 pmLikewiseQuote from: tggzzz on November 21, 2021, 10:52:30 pmIndeed, but anyone who goes around reversing every piece of equipment before trying to obtain schematics/manuals has way too much time on their hands.Quote from: tggzzz on November 21, 2021, 10:52:30 pmFor this particular item it's 440K at the 1.1 input and 400K at the 1.0 input - both +/- 0.02%Quote from: tggzzz on November 21, 2021, 10:52:30 pmThe unknown provenance, age, all those things to twiddle and the "Do not use" tag give me reason not to trust just yet

author: tggzzz
author_rank: Super Contributor
timestamp: November 22, 2021, 12:50:56 am
content: Quote from: rigrunner on November 22, 2021, 12:26:45 amHave youlookedat the schematic for a KVD? It issimple!QuoteIf you are going to twiddle, you will need 7 digit equipment. If you don't have that, don't twiddle.

author: rigrunner
author_rank: Frequent Contributor
timestamp: November 22, 2021, 01:28:24 am
content: Quote from: tggzzz on November 22, 2021, 12:50:56 amI 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.

author: veedub565
author_rank: Frequent Contributor
timestamp: November 22, 2021, 10:21:54 am
content: There's some info on the 720A herehttps://xdevs.com/fix/f720a/

author: tggzzz
author_rank: Super Contributor
timestamp: November 22, 2021, 10:26:18 am
content: Quote from: rigrunner on November 22, 2021, 01:28:24 amIf by that you mean you have 7 digit equipment, then out of curiosity, what is it?

author: rigrunner
author_rank: Frequent Contributor
timestamp: November 22, 2021, 06:52:59 pm
content: Quote from: veedub565 on November 22, 2021, 10:21:54 amThat 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."Quote from: tggzzz on November 22, 2021, 10:26:18 amA few 8.5 digit meters. A couple of Datrons, a couple of Solartrons and a nearly useful Transmille.