The white ¡°knobs¡± on the top of the flanges for the circuit cards are specifically for pulling the cards from the motherboard/card cage. Some of the cards have gold plated side edges that mate to brass or gold plated tension plates in the card cage - all done to reduce RFI.
Occasionally you will find spurious RF signals on the display that relate to frequencies found in the 85660A/B RF section. The first thing to do is check all of the screws in the A6 section for tightness while watching the displayed spurious signal of interest. If not solved then closely inspect the card cage for a whitish gray corrosion around any of the A6 assemblies, if found remove that assembly and clean both the card flange and card cage mating surfaces with an eraser until shiny, that should solve the spurious emission. Very rarely you may find corrosion on the bottom of the card cage where it mates with the motherboard. If that happens, then remove all the cards in the cage remove the cage, clean the mating surfaces as above and reassemble.
You should be able to isolate the specific assembly radiating the spurious signal based on the signal frequency and the RF section/A6 theory of operation and troubleshooting.
Don Bitters
