I just realised that with the dials set for zero that R311 will be shunted by the following decades. I think that with the A dial set for 0.8 that a measurement of R311 should be valid.
If that's right, then I get 9K79 which still seems low. Dave -----Original Message----- From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of David C. Partridge Sent: 10 July 2017 13:13 To: 'Discussion of precise voltage measurement' Subject: Re: [volt-nuts] Problems with 720A If I have read that right I'm getting what I think are "odd" readings across R302 (9K710) (pins 21-22) and R311 (7K395) (pins 3-4) when the dials are set to all zero. I think both should read about 9K9. Could someone who has a 720A check the resistance across pins 21-22 and 3-4 on the oil bath and let me know the numbers? Thanks Dave -----Original Message----- From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of David C. Partridge Sent: 10 July 2017 12:20 To: 'Discussion of precise voltage measurement' Subject: [volt-nuts] Problems with 720A You knew this was coming I'm sure: It was almost inevitable that there would be problems with the 720A! While trying to self-calibrate the 720A, (CAL A) the at the 0.1 and 0.10 settings the null meter was way out with around 100mV out of balance, and the A.1 and A.10 pots seemed not to do anything. I'm trying to work out from the schematic what's likely to be wrong, but so far am not clear where the fault lies. I *think* that when I have the main switch set to CAL A and the A decade set to 0.1 that I'm balancing R311, R1044, R1042 and R1041 against the leg of the bridge comprising R1, R206, R207, R208 and R209 Similarly for the 1.0 setting of the A decade, I think the resistors are R302, R1008, R1006, and R1005. Have I read this correctly? Thanks Dave _______________________________________________ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. _______________________________________________ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. _______________________________________________ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
