I got an EPS-1 DC-DC converter in a horse trade about a year ago
and thought it would be a cool addition to my KX1 to jump the
9Volt internal batteries up to 12Volts.
The EPS1 was either dead when I received it or I killed it
because when I plugged it in to a battery source as the switching FET surface
mount transistor caught on fire!
It looked like one of those 4th of July "snakes" burning only
with sparklies.
I let it set on the shelf for a while and then tried a
couple of times to resurrect it with no luck. I tried
replacing the blown FET with a 2N7000 but it didnt work.
I then ordered a new MAX1771 DC-DC converter controller chip
and when replaced the one on the EPS-1 board with the new one
it started putting out 12 volts with about 4 volts in.
I experimented with load resistors and it was clear the 2N7000
switching FET would not handle the current so I swapped it out
for a Radio Shack IRF510. The IRF510 didnt even get warm with
an amp load so I tried running the KX1 off of the modified
EPS-1. It worked great. I was getting 12 volts from
a little 9 volt battery and was getting full power out of the KX1
rather than the lower output I get when running off the internal
9Volt batteries.
I thought I could just disconnect one of the 4.5V AA packs in the
KX1 and then put the EPS-1 inside of the KX1 but it turned out
that 4.5 volts was too low to get reliable switching from the EPS-1.
I then went to Radio-Shack and picked up a 4-AAA battery holder
(RS270-411) which fits nicely into the space of one of the AA
original battery holders. I removed both original battery
holders and installed the EPS-1 where the other original holder
was.
It worked FB. I had to cut a small hole in the back of the
case so that I could access the RS770-411 on/off switch and
used double sided foam tape to secure the EPS-1 and battery
pack.
I have no idea how long the batteries will last. I do know
that I have had the KX1 for a couple of years and have only
changed the batteries once in that time so I imagine that
they will last long enough for my use. Ill see.
EMBRES no longer makes the EPS-1 but the schematic is
pretty simple and comes pretty much right off the datasheet.
Maxim-IC makes a litle MAX1771 evaluation kit that might
be a direct replacement for the EPS-1 although I dont
know how much it costs.
Useful links:
http://pdfserv.maxim-ic.com/en/ds/MAX1771EVKIT.pdfhttp://www.maxim-ic.com/quick_view2.cfm/qv_pk/1030http://pdfserv.maxim-ic.com/en/ds/MAX1771.pdf
Have Fun
Mike
KL7R
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