I've got one of my Hickok LS 15874 L2 Cardmatics going. I cleaned, lubed
and realigned the switch matrix as well as other switches and also found a
cold solder joint from a previous repair. About 100 of the switch matrix
pins had what looked like old paper capacitor wax on them, very sticky! I
took all the pins out, cleaned each one and the sockets. (An ultrasonic
cleaner would have been nice.) It took several attempts to get the
clearance correct, since the jam nut moved but I finally figured out a
system. Now it appears to test tubes just fine but it still has one problem
that escapes me and wonder if anyone would have any ideas. It responds per
the manual to all test cards except card 9, Gm, Low Ib. About half the time
card 9 will kick power off and I'm guessing it's because the meter kicks
backwards below zero when button 2 is pressed When it doesn't I can adjust
Low Ib per the manual and seems to work fine. However sometimes the meter
needle doesn't go below zero enough to kick the power out but when this
happens the Ib control has no effect! Any ides or tips appreciated.

73
hank wd5jfr