That's quite a bit different from the PS in the Z3801A.
From the pictures, I'd guess that the "A" and "B" markings on the DIP
switch are for 24 or 48 V AC or DC Battery operation. I did a little
looking around, and found this:
http://www.realhamradio.com/GPS_Z3816A_Receiver.htm
It says that it supposedly can run on 120 VAC, but the circuitry on your
board doesn't look like it can support it as is. If you blow up the
little picture of the back panel on the website, it sure looks like a
standard IEC line power cord is plugged in, but the text is illegible.
If you investigate more, you may find the official specs and appearance.
The empty space on the PS board looks like it can possibly fit a small
AC SMPS circuit, but the layout is not appropriate for line voltage -
the clearances are way too small for it to be proper, safety-wise. This
means that it probably is not where line power would go, and the only
other place might be in the main power section, over by the big cap. The
problem with this scenario is that cap is way big in C (2200 uF), and
way short on voltage rating (100 V) for line input. It could be that
there was a line voltage option, that entailed using some different
parts in the main section, plus maybe some things to fill up the empty
zone. Instead of having anything to do with line power, that space may
be for a 12 V option. There is a "12" spot on the DIP switch, and some
text on the board about power ratings with the different voltages.
Another possibility is that a transformer could could go in, to run from
line voltage to make low AC - 24 or 48 Vrms. But, it would need to be in
the 50-100 VA size range, kind of big to squeeze into the cabinet. Look
at the mechanical features of the cabinet to see if there are extra
holes and such to mount more stuff in there.
Anyway, as it appears to me, the DIP switch sets up the power control
functions such as UVLO, OVLO (or OVP crowbar), and maybe power-on/reset
signalling, depending on the power source type and nominal voltage. One
thing to double check is how much polarity matters. If it can run on low
voltage AC already, then it probably has a bridge rectifier input, so it
won't care about the DC polarity. If it really is for DC-only, then
there's probably a blocking rectifier for RVP, or less likely a shunt
rectifier that will blow the input fuse for RVP. A little inspection and
reverse engineering will tell you what the deal is.
It should self-protect, so you can try setting it for "24B," and put in
24 VDC from a supply. Don't forget about the negative input R that will
make it draw more current at lower input voltages - the supply has to
put out enough current to handle it, once the input voltage gets high
enough that it decides to turn on. It looks like this model takes way
less juice than say, the Z3801A, but the same tendency will be there.
Ed
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