[Test-Equipment] HP 141T spectrum analyzer question

Thu, 2 Jan 2003 21:23:05 -0800 (PST)

Greg,

Had the same problem in my 141T mainframe. The cause
is the high voltage multiplier, after a number of
years the ceramic capacitors start to break down, the
bumps that you are seeing on the display are the
actual momentary breakdown of one or more of the
capacitors. As I recall they are door knob style caps
and the caps and rectifiers are potted in RTV. It took
me quite a while to dig all the silicon poting
compound out of the multiplier assembly to the point
where I could unsolder the defective parts and replace
them, as I recall I did a wholesale cap replacement
just to make sure the problem would not come back. As
an alternative you might be able to find a whole
multiplier assemply out of another doner unit and swap
it out, I have done this before also.

Good Luck

Mark Donaldson (WA1QHQ)
--- greg mijal <[email protected]> wrote:
> Hi all:
> 
> I have a problem with my HP 141t spectrum analyzer
> and I can use your
> expertise to help get it back into good health
> again.
> 
> Here's the problem:
> 
> The analyzer sweeps and has sensitivity.  However, 
> the straight line
> trace at the bottom of the screen is no longer flat.
>  It has a series of
> bumps in it and they walk accross the screen while
> the analyzer is
> scanning.  If I insert the 30 mhz cal signal into
> the main input, the
> bumps keep walking thru the trace, up, over and down
> the cal signal too.
> The "walking bumps" also seem to cause the displayed
> cal signal to
> jitter.  I looked at the vertical output bnc of the
> analyzer with an
> oscilloscope and there is no sign of the bumps but
> the cal signal is
> jittering along with the main trace.  I have manuals
> for all
> sub-assemblys and can follow along with your advice.
> I think I have a problem with the display unit.
> Any advice out there?
> Thanks!!
> 
> Greg
> in sunny Feenix
> 
> 
> _______________________________________________
> Test-Equipment mailing list
> [email protected]
>
http://mailman.qth.net/mailman/listinfo/test-equipment

__________________________________________________
Do you Yahoo!?
Yahoo! Mail Plus - Powerful. Affordable. Sign up now.
http://mailplus.yahoo.com