[time-nuts] Varian 921-0062 ion pump supply question

Robert Atkinson robert8rpi at yahoo.co.uk
Fri Sep 20 11:31:13 UTC 2013


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: "cdelect at juno.com" <cdelect at juno.com>
To: time-nuts at febo.com 
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

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