Today is "no good deed goes unpunished"...
Yesterday assembled four 15-pin extender cards (had the PCBs made a long time ago, but never built the 15-pin versions til yesterday.)
Initial goal has been to carry out verification and attempted adjustment of SL1's synthesizer which appears to be the source of the wandering problem in the 20-30 MHz composite signal provided to the RF plug-in. The 8660B service manual section 5-33 (adjustments for SL1) specifies test points (A2TPxxx) that are on the motherboard's top side, and adjustments made via the bottom side (enclosed PCB area). The four test point signals are also accessible on PCBs A15 and A19 (bottom side), hence the extender board idea. Photo attached of the two boards on their (new) extenders.
(photo attached)
Restarted the synthesizer in this configuration (no smoke emerging), counter attached to the 20-30 MHz port of 11707A, the signal there is now stable (not wandering). Checked this across it's working range (settings xxx0000000 to xxx9999999 Hz) and the 11707A 20-30 MHz output frequency appears stable. No components have been replaced, and after the synthesizer started showing the wandering problem, the problem persisted until now.
At this point I'm going to put the A15 and A19 boards back into normal position and reattach their shield covers and see if the problem reappears.
