Hi Corby, about the C field ten turn pot you write is a low TC pot. Normally a good Vishay pot is 20 PPM/C, This is in conflict with the 1PPM resistors ad voltage reference. What kind of pot do you have used? http://www.mouser.com/ds/2/427/533534-768216.pdf Luciano timeok
Da "time-nuts" [email protected] A [email protected] Cc Data Fri, 17 Nov 2017 12:37:57 -0800 Oggetto [time-nuts] HP5065A C-field mods and optical unit mods Luciano, The TX and choke and filter caps were removed as I had envisioned I would have to re-mount the A1 and A7 in their location. However with some judicious movement of the mounting holes I was able to squeeze them in close to their original spots. The 5065 chassis was removed and inserted into a chassis from an HP 8405A. (just used the side panels and the rear panel.) I'll post a schematic of the new C-field supply next week. It consists of two LM299AH in series feeding a string consisting of a 2.4K, 1k, 1K and a 1K low TC pot. A switch allows you to short out one or both of the 1K resistors as a coarse adjustment. All resistor are 1PPM. Fixing the 20Volt and the C-field temperature contributions allowed me to isolate the optical units changes due to temp. The resistor thermistor combo I mentioned would be taped to the optical unit and compensate it only. It would be in series with the C-field coil. Not needed in my unit but thought that others might want to try it rather than getting as complex as I have. Yes the active baro and temp circuit would be an alternative for a unit without my mods. attached are PIX of the enclosed optical unit and the front panel. Cheers, Corby _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
