Don,
Thanks for the suggestions. Please see my replies below:
Mike,
I believe I have an 853A/8559A system, but I have not touched it in years.
To get back to the problem, you said that you have no display - no display as
in a totally blank display with no freq., span, sweep time, etc. indications -
then check the supplies in the mainframe, or no display as in no signals
displayed, just the displayed noise floor.
Mike: I have a display with no signals displayed. The freq, span, sweep, atten,
etc, seem to work.
In the 3MHz bw, 10MHz span, 10dB/div, 10dB atten. settings you should see the
noise floor about -50, -60dB down from top 0dB reference.
Mike: I see the noise floor at the bottom of the display -80dBm level.
Tune the freq. down through 0Hz in >10MHz span/div or in full span. You
should see the L.O. feed through signal at about -25 to -35dBm level, if it is
significantly higher than that, probable zapped first mixer.
Mike: I don't se the L.O. feed through any more.
If noise floor but no signal of any kind then there are RF or IF path signal
problems. You can check 1st, 2nd, 3rd L.O. power levels and freq. with another
SA or power meter. You can also signal inject the 3rd IF (21.4MHz) via the
jumpers or smb connectors on the top of the 8559A. Tuning around the IF freq.
of 21.4MHz will get you baseline lift to the ref line of the display. You can
then check the atten., ref level per div and linear scaling and steps. This is
best done with the manual and block diagrams in front of you.
Mike: I'll start to check it out. Can I do these checks with just the top cover
removed from the case? I don't have any card extenders,
I have repaired, aligned, calibrated over 100 of this series SA¡¯s over the
last 40yrs.
If you need further assistance you may text me back using the forum or my
email.
Don Bitters
Mike: Depending on what I find I will reply directly or via the forum.
