[Premium-Rx] HF-2050 power supply tap change

[Paul Wende]

>Paul,
>
>Where is the 130v AC tap ???? Do you have a picture of its location ?
>
>Rodney
>VK2KTZ
>I suspect the only HF-2050 in Australia .....

Sorry Rodney,

I didn't think to take a picture of it while it was apart. I will describe
it though as it's very easy to do.

You can either move the pins in the internal plug or remove the power supply
and de-solder the wires on the xfmr. I chose to move the pins in the plug.

A quick note before you begin. From what I have read in the Ops manual. Some
of these radios were wired for a fixed 115VAC, with no way to change the
taps from outside the radio. ie. in the fuse holder, AC input box. Mine is
this type, I think they are the -001, -002 and -003 suffix in the part
number.

Lift the top cover of the radio, there is an internal white Molex type 4 pin
connector going from the power supply, tie wrapped to another white wire.
Disconnect the connector and note that one end is pointed. That is the
common lead, or 0 VAC. Then the next ones beside it are 105 - 115 - 125. If
you look closely down at the pins in the housing on the end that goes to the
supply, you will see that there are tiny barbs keeping the pin from pushing
out the back of the connector. You need to compress these slightly and
simultaneously (quite an exercise in patience) and then push the pin out the
back of the connector. I swapped the 115 and 125 pins as there are only 2
wires in the other half of the connector and you need to continue using pin
1 and 3. That's all there is to it. Please make a note and attach it to the
wires so any future owner knows what has been done.

The other method requires removal of the supply from the radio and is
equally simple. This reminds me of the automotive manuals that are
deceivingly simple on the surface, yet once you read them, realize the job
is much more work than the number of pages indicate. For example, to change
the water pump, no problem, only a few lines in the manual. Should only take
half hour. Well step one is, drain the cooling system 2. Drain the A/C
system 3. Remove A/C compressor 4. Remove radiator and on and on it goes
until you get to the 6 bolts holding the water pump. By this time it's
Tuesday. :-)  Anyway, step 1. Remove the power supply, remove the 4 screws
holding the cover over the wires. The wire on the left is the common, and
they follow the same order left to right. 0 - 105 - 115 - 125. Just
de-solder and swap the 2 wires on the left and your done. Again, make an
internal note to remind you or future owners what has been done. You can
confirm before you plug in by measuring the DC R of the transformer primary.
>From the common to the other leads, low tap starts at ~ 5.5 Ohm and goes up
about .3 ohms for each tap. If you are measuring .3 ohms between taps, then
you haven't found the common lead yet and are measuring between 2 taps.

If I ever take the supply out again, I will remember to take a few pics.

Good luck,

Paul
VE7KHz