Hi Corby, I had a look at some circuits and it’s pretty much what I expected. The 120V tap supplies control relays including the external pressure relay (pin F on rear panel connector, pin E is neutral) and neon indicators. The supply to the HV transformer is relay controlled so you would have to bypass that to do the low voltage power-up trick. The four terminal transformer has odd numbering with one winding between 1 & 3 and the other between 2 & 4. This allows the same rigid shorting links to be used for both 120 and 240V, one each between 1&2 and 3&4 for 120V and two stacked between 3&4 for 240V. The safe option would be to apply 12V ac across 1&3 with no links and check the voltages and phase on the other windings and taps. The secondary should be 1/10 of that expected. If it high you need to use the additional taps on terminals 8&9. One possibility is that these taps are an alternative to a tapped secondary for HV adjustment. For 120V input the extra tap wire should be connected to the input supply so you have line voltage across pins E &F of the pressure relay connector. Don’t forget that there is another switch or links on the control PCB for the small transformer. HTH Robert G8RPI.
________________________________ From: "[email protected]" <[email protected]> To: [email protected] Sent: Thursday, 19 September 2013, 22:56 Subject: [time-nuts] Varian 921-0062 ion pump supply question Here is the deal. The 4 terminal TX wiring is pretty obvious. (I have a unit with the 4 terminal to compare with) The 6 terminal I have ohmed out and it is not obvious! Pins 1 to 3 and 2 to 4 (.5 Ohms) appear to be the 120VAC windings and hooking them in parallel should do the trick. As wired for 240 VAC 1 to 3 and 2 to 4 are in series which makes sense. However when the 4 terminal is wired for 240VAC a wire comes off the input center tap to provide 120VAC to some circuits in the unit. The 6 terminal when wired for 240VAC has an extra wire connected to pin 8. Pin 8 to 1 and pin 9 to 2 show .2 Ohms so they look like maybe taps for a different input voltage slightly different from 120VAC. The problem there is that the wire to pin 8 which would logically go to the center tap as above goes to this pin 8 tap which makes no sense! Of course it could have been miswired when I got it! All the manuals I can find by Goggling show the 4 pin TX! Was hoping someone might have a unit with the 6 pin TX wired for 120VAC so they could advise me! Thanks, 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. _______________________________________________ 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.
