My 2753P Spectrum analyzer gave me the scare of my life.
I had not used the unit in about a month, but tonight I built
a filter and I had to see the response. I have a TR503
Tracking generator and both units are perfect
for checking filter bandwidth.
I had the 2753P on for about five minutes, and all of a sudden,
the display went nuts and all the front panel lights
wend black. The display still showed something but it was garbage.
All the front panel switches/buttons were dead except
the Peak/Average control which still managed to move the
averaging line up/down on the screen. Everything else was dead!
So I turned the machine off, unplugged the TR503, and put
50Ohm terminators on the 1stLo, 2ndLo SMA outputs.
I turned the machine on again, after 10 minutes, and all was
dead again. At this point, you can imagine how I felt.
There it was, my very nice (and expensive) spectrum analyzer
dead as a doornail.
I figured, here comes a very long troubleshooting session.
So I take the instrument down, and take out all the panels.
I don't have the Schematic Manual (That is volume two)
so I was really worried that I would be without my spectrum
analyzer for a very long time.
So I re-seat all the cards, and still nothing. I check the output
of the calibrator on my scope, and it was fine.
As a last resort, I moved the Time/Div knob from "AUTO"
to 1ms. Guess what..... The front panel flashed!!!!!!!!!
I left the Time/Div knob to 1ms, and I turned off the unit.
When I turned on the unit, all the front panel controls
became functional and the unit came back to life.
But still no signal on the display.
I figured the front end had kicked the bucket. I tried the
calibrate procedure and it failed right away.
At this point I became very depressed. I don't think
the front-end components of 2753P are still made.
However, by mistake I ran the calibration routine
with the Time/Div on 1ms and when it finished,
I could see some response on the display.
Sure enough, when I put the Time/Div back to
Auto, and ran the calibration routine, it passed.
The machine is now fully operational.
I have no idea what happened, and no idea
how it was fixed. I am just grateful that my spectrum
analyzer is alive again. I felt "blind" without it.
Sorry for the long post.
George Hrysanthopoulos, N2FGX
