[time-nuts] KS-24361 Power Module Repair

Chuck Harris cfharris at erols.com
Sat Apr 11 00:52:18 EDT 2015

That is almost a carbon copy description of how I fixed a
similar module in my Ball/Efratom MGPS unit on my GPSRb

An oven set to 140C is your friend when doing jobs like

The guys that make these modules are trying to make them
as small as possible, so they always use tantalum capacitors,
and run them very close to their ratings... in this case, it
was 18V on a 20V cap.

This particular module had +/- 15V, and +5V on board.  I have
never seen so many individual switching power supplies stuffed
into a single module... They were all little 5 terminal IC's,
with each running at whatever frequency it felt like...

-Chuck Harris

Bob Stewart wrote:
> This is just a brief report, not a how-to.
> I got a KS_24361 with a bad Lucent power module.  Having nothing to lose I thought
> I'd see if it came apart.  After unsoldering it from the motherboard, I found the
> usual potting compound.  Fortunately, the compound was only loosely attached to
> the board in the brick and was easy to pick off.  After that, I used a pair of
> needle-nose pliers to work the board out of the casing.  In spite of the pic
> below, I first gently pried up on the corners, in succession, until the corners
> released.  Then I worked my way toward the middle, until the board came out.  Be
> aware that there are two small inductors on the top side of the board that have
> metal covers that will probably stay in the potting compound.  Just leave them
> there.  When you push it all back together the covers will go back on the
> inductors.
> http://evoria.net/AE6RV/KS/OpenUp.jpg One corner of the brick was pretty hot while
> I had it on, so I figured there was a shorted component.  As it turned out, it was
> a 15uF tantalum cap with a big brown spot on it.
> http://evoria.net/AE6RV/KS/BadCap.jpg Here's the cap removed from the board at the
> upper left. http://evoria.net/AE6RV/KS/CapRemoved.jpg
> So, ordered the cap, put it on the board, then just pushed the pins into the
> motherboard for testing.  I didn't even bother soldering it.
> http://evoria.net/AE6RV/KS/Testing.jpg Tests were good, so I stuffed the board
> back into the casing, and soldered it all back on the motherboard.  I didn't
> bother repotting the bottom surface of the board.  I attached the repaired KS to
> my good REF-0, and it's now working. Bob - AE6RV
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