I have a problem with my 141T/8555A spectrum analyzer. The gear works perfect in the conventional mode, but it will not store. When I push the "store" button, the screen simply goes blank. Pushing either the STD or FAST button makes it operate as a conventional CRT.
Don Collie has very generously swapped my pulse circuit board in his analyzer and has confirmed that the pulse board is OK. Indeed I have checked all voltages and waveforms / amplitudes on the pulse board and confirmed that they operate as expected. I have also checked all supply voltages and adjusted them to be spot on. The voltages at the various pins of the CRT have been checked, including the -12.6V heater voltage for the flood gun and are all within limits. I have not checked the heater voltage for the main gun, as the unit operates fine as a conventional analyzer. Similarly I have not checked the
6.6KV supply, as the unit is fine in conventional mode. I did check the voltage at the anode of CR23, which is -1350V as specified. The voltage at the anode of CR24 varies between -2518V to 1591V in what I would describe as being almost a saw tooth like fashion. Perhaps the experts can find a clue in this observation.
In sheer desperation I replaced the CRT with a brand new one I have, (which of course includes a brand new infamous 3 conductor ribbon cable), but it has not solved the problem. In other words everything is fine as a conventional analyzer, but when the "store" button is pushed, nothing changes. Again voltages have been re-checked and re-adjusted and are as expected according to the circuit diagram.
I cannot perform the pulse circuit adjustments described in section 5-0 of the manual, simply because I cannot get past sub paragraph f, which requires the fast collimator adjustment A5R14B to be adjusted so that the entire flood gun illumination is visible. I cannot get any illumination whatsoever.
I would be grateful for any suggestions as to what my next move(s) should be.
Cheers,
Chris
