The AM Forum

Does anyone have a diagram of an S-22 that shows how the terminals are numbered ? I have found the impedance jumper charts, but there are no numbers
or markings on the xfmr case.. No terminal charts in any of the online UTC catalogs that I have found..Tnx  W5FRS

Try this. Hopefully it's the same. Hope it helps.

Bob - Thanks for the pix.. But, my unit must be older because it has 3 rows of terminals with threaded studs and 6/32 nuts.. I am sure it's an S-22 because the model tag is still on the case.. 

I don't have an S-22 but I have a VM-3 which might be the same

73 Jack KZ5A

Here's a smaller version, sorry for the huge file ::)

Thanks for the pix.. But my unit has 2 rows of 6 terminals and one row with 2 terminals.. The terminals are feed-thru with 6/32 nuts on them.. Must be the first version of this model ..

Are you sure it's an S-22?  All the UTC's I have come across are solder terminals.  Can you post a picture? Might make for some interesting discussion.  Sorry I couldn't help.

Sorry, but I don't have digital camera / pix. Yes I am certain it's an S-22 because the original metal (model) tag is on the case. It must be the first version of the xfmr that had threaded studs. It was salvaged from a very old home built modulator chassis. If maybe someone has a diagram of the windings, I may be able to figure out the terminal numbers.

On one side, the transformer has two winding each with two taps for a total of 8 pins.

On the other side, the S-22 has two windings each with a single tap for a total of 6 pins.

I'm guessing the two pins that are in a row by themselves are pins 13 and 14 in this chart:

http://www.amwindow.org/tech/htm/modtran/utc/sseries.htm

(only the S-22 had pins 13 and 14. The other S series had only 12 total pins).

Should be pretty easy to figure out.

Note that depending on the ratios you want and the pins you select, either "side" can be the primary.

Yes, the windings / taps info will let me decrypt the terminals .. I sure hope the old unit is still good .. I have a rig waiting for it..  Thanks a bunch !

Using some low voltage AC (20v-30v) you can figure out the whole xfmr ratios.  Apply some AC to one winding and measure the voltage on a winding on the other side of the xfmr.  With careful measurements you can figure out the turns ratios.  Example, you apply 20v on one side and you measure 30v on the other side.  Turns ratio is 1:1.5, impedance ratio is the square of the turns ratio.  In the example it would be 1:2.25.  So if you had an impedance of 1000ohms on one side it will match to 2250ohms on the other side.

Of course you have to phase the two windings on each side and also measure the voltages off the taps.

Usually on most multi-tap mod xfmrs there is an over all slight step-up in the turns ratio from side to the other.  Either side of these type xfmrs can be used as the primary or secondary.

If you need more help let us know.

Fred

Thanks to everyone for the info and pix.. Think I've got it figured out.. 73 de W5FRS Dennis