I recently bought a KSB2 that was advertised here. It's an early release,
rev B board, so I picked up a number of update kits and started assembly,
slowly and carefully, as Gary advises. I got through it in a couple
of evenings.
Last night, I installed it in my K2 and got INFO 080. Drat! I was so
slow and careful! I checked voltages on the MCU, they were fine, so
I got the silly scope out to see if there was AUXBUS traffic on pin 28
where there should be.
Yes, there was. And ... also on pin 27! That can't be good. I inspected
carefully for solder bridges, found none. I contemplated diking out
part of the socket to ease removal. Gary suggested heating the pins
and wiggling. Ultimately, I clamped the thing in the vise, put on
my finest soldering tip, and sucked up the solder, pin by pin. After
about three passes, I was able to remove the socket, intact, and
no damage was done to the board.
I inspect the socket, no joy.
I inspect the top of the board ... no joy!
Pins 27 and 28 are 0.1 ohms. Drat.
I lift R12 to isolate that part of the board ... still beeping.
Bright light, magnifier, ask my XYL to look, too. Nothing. Finally
decide to put it away for the night.
Then I go give it one more. I thought that perhaps the trace
that comes off pin 27 had grown too much and was touching the pad for 28,
so I scraped away the solder mask. No joy.
I started contemplating where I could cut a trace to divide the problem
and still make a reasonable, perhaps invisible repair. As I did, I noticed
a slightly darker spot around pin 1, between the traces from 27 and 28.
Sure enough, there must have been just a stray bit of resist laid
down there, about half a hair's width, because there was copper under
the mask connecting the traces.
Free! Free! Pins 27 and 28 are free again! It's tempting, but I'm not
going to rush soldering the socket back in and then rush a test. I'll
do it tomorrow when I can go through the whole procedure and update
the front panel, too.
One for the archives...
73 de chris K6DBG
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