[Test-Equipment] textronix 2710 analyzer problem

[TK5EP (Patrick Egloff)]

Hi All,

Thanks to this list i could find a xtal to repair my Textronix 2710 spectrum analyzer. 

Now it works normaly except i small intermittent problem :

I have a lot of parasitics signals equaly spaced. The spectrum is very wide, almost all the spam of the instrument and unstable in frequency, it shifts up and down.

They are not coming from the RF input, amplitude does not vary with input level nor with SPAN.

Only the SWEEP rate is making a change in the spacing on the display.
at 2ms sweep rate i have approximatively 1 spike every 5 divisions
at 5 ms approx every 2 
at 10 ms approx every 1 

It does not occur each time i start the instrument, but once it started it does not seem to stop. It can restart at next power ON or not....
It does not seem to affect the measures.

Has anyone an idea of what this can be ? It looks like a 100 Hz parasitic oscillation, but where ??

Thanks for any idea. Patrick on Corsica.