[time-nuts] Another KS-24361 REF1 DOA, investigation

Orin Eman orin.eman at gmail.com
Tue Aug 11 02:40:33 EDT 2015

I ended up with a dead REF1, so I decided to investigate.

The -15V was at -0.6V and the 15V at 3.5V.  The power module was hot
to the touch.

Then I found Bob Stewart's post from a few months back, so I decided
to pull the power module and check the capacitors.  First, I measured
the resistance of the power rails to ground.  15V was about 1k and
-15V 0.9 ohm, so I was pretty sure it was one of the tantalum

The pins in the power module are not well seated.  Two came loose just
under the influence of my Hakko 808.  A third broke off while pulling
out the circuit board.  The potting compound came off the bottom in
big chunks, no problem at all.  Some of the potting compound stayed on
the top of the board, but not over the offending capacitors.

I removed the capacitor from the -15V output and it measures about 1.0
ohms, so its definitely dead.

For the record, it is 15 uF, 25V (and the capacitor on the 15V output
is the same).

I happened to have some 10uF 35V surface mount tantalum capacitors
around, so I soldered one in place of the original part for test
purposes (I'd have used two in parallel if they would have fit; I
doubt that the value is critical), fixed the broken pins and did the
push it into the holes trick... I applied power and it flashes its
LEDs as expected.

So, time to order up a few 15uF >= 25V caps.  I'll be replacing both
before putting it all back together!


*I had 35V rated parts around to get a low ESR, I use them with an
LT1763-3.3 that wants < 3 ohms ESR on its output.

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