David, Yeah, I was expecting a hefty price tag on a relay of that variety. Seems that anything that has "Low EMF" in its description is expensive. I'm kinda surprised that a replacement was so readily available. My luck with things of this nature has been nonexistence except in a museum. Good luck with your repair. David M
----- Original Message ----- From: "David C. Partridge via volt-nuts" <[email protected]> To: "Discussion of precise voltage measurement" <[email protected]> Cc: "David C. Partridge" <[email protected]> Sent: Tuesday, October 21, 2025 11:48:58 AM Subject: [volt-nuts] Re: Problem with Solartron 7071 I've checked and I think that a 3602-05-52 is a good replacement. Not cheap mind you ☹ Coto of course didn't reply to my enquiry ☹ David -----Original Message----- From: DM via volt-nuts <[email protected]> Sent: 17 October 2025 17:17 To: Discussion of precise voltage measurement <[email protected]> Cc: DM <[email protected]> Subject: [volt-nuts] Re: Problem with Solartron 7071 David, The Coto 3400 Series relays were low thermal EMF relays. I've attached a PDF of some pages from old EEM catalogs (the Internet Archive has them for download). Sketchy information at best; I haven't found a catalog of the complete 3400 series relays. Coto still produces low thermal EMF relays in the 3500 & 3600 series. Don't know if either of these would be a good fit for your instrument, or if they're available from any of the usual suppliers. You didn't describe your relay as to form factor, coil & contact arrangements, but there are several Coto 3400 series relays listed on Ebay. With a little Yankee Ingenuity, maybe one of them could be adopted by your insrument. Good luch with your search. David Mason Alabama, USA ----- Original Message ----- From: "David C. Partridge via volt-nuts" <[email protected]> To: "Discussion of precise voltage measurement" <[email protected]> Cc: "David C. Partridge" <[email protected]> Sent: Friday, October 17, 2025 5:23:01 AM Subject: [volt-nuts] Re: Problem with Solartron 7071 Looks like RL5 in the input attenuator circuit isn't opening fully, so above a certain voltage it lets the voltage on its input through to the input of DC ranging circuit. It is a Coto 3400-0051. I can't find any information about that so don't know a suitable replacement. Does anyone have either a) any of these relays to spare, or b) know of a replacement? Thanks David _______________________________________________ volt-nuts mailing list -- [email protected] -- To unsubscribe send an email to [email protected] To unsubscribe, go to and follow the instructions there. _______________________________________________ volt-nuts mailing list -- [email protected] -- To unsubscribe send an email to [email protected] To unsubscribe, go to and follow the instructions there. _______________________________________________ volt-nuts mailing list -- [email protected] -- To unsubscribe send an email to [email protected] To unsubscribe, go to and follow the instructions there.
