The phrase ‘poke around’ is synonymous with fault finding, especially when you have
limited information, However when there is potentially 4KV present, poking around
takes on a whole new dimension. I found an open-
A quick test showed that the Sweep Oscillator worked and so did the Lin/Log Amplifier module. With the display now working all I had to do now was figure out how the SA.97 was actually used.
There are 4 connectors on the front panel; two BNC and two mini-
As already said, the Marker Generator, employs four valves, one ECC81, two EF91s
and an EFC80. The latter appeared to be faulty; the triode section causing the trip
on my valve tester to assert. I didn’t have a spare, so I had to order one. In the
interim I set about working out the circuit diagram ... not as hard as it looks.
Once I had an idea of the different parts of the circuit, it was just a case of following
the signals through each ‘block’ and trying to figure out why one of the pulses would
diminish. I then decided to replace all the half-
remained constant, so I must have done something right. But only two markers still didn’t ‘feel’ right, so I played around with the two variable inductors. I figured it would be logical to have a centre marker and at least one on either side. So I also played around with the sweep width controls and finally got the trace on the left. Definitely one centre marker with two either side. Not bad for no cct. Diag. and no idea how it worked!
Marker Generator underside