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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

I figured the front end had kicked the bucket. I tried the
calibrate procedure and it failed right away.

Why would you assume that? This failure wouldn't have anything to do with
the front end. It sounds like a CPU glitch of some sort. The problem's not
likely to be gone forever, but not likely to put the analyzer totally out of
commission, either.

If it happens again, try turning off digital storage and see if that makes a
difference.

-- john KE5FX

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.

It is both a massive relief and deeply worrying when this sort of thing
happens. My 7L5 has got a similar quirk - the spectrum will shoot off
800kHz up the display from the reference dot - and then will come back and
jitter around, settle down for a while then - back up to 800kHz.

OK - an intermittent fault I hear you say - probably in the PLL. Heh - so
far it has defied attempts to find it; seems to obey some qunatum mechanical
behaviour: as soon as you offer it violence by trying to fix it, it settles
down for a few hours. Until I really want to use it again, that is.

But good luck with the 2753P - at least like my 7L5, it isn't *really* bust,
just being an awkward SOB.

Craig