I fixed the 7B53As. The board mounting screws on one of the
inner boards were loose. Tightned the screws and both
the 7B53As now behave themselves.
I had exactly that problem with my 7B85. One of the spacer pillars was
loose - and this particular one was necessary to ensure ground continuity
between the boards. Symptom was that the readout on the CRT display was
intermittent.
Craig
