Products > Test Equipment
HP 8595E spectrum analyzer repair
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Tracker:
Hello Kaka and MarkL,
Just been reading this thread with great interest
I believe I may have a similar problem on my 8595E, but also with a temperature related issue on Band 0

Problem 1:
Band 0 works for a short period, but after 10 minutes warm up and connected to 300 MHz Cal, the Cal signal gradually drops by 15db, then finally at -36dBm it drifts off frequency and the FREQ UNCAL error appears.
I checked and proved the actual cal signal is good an 300MHz -20 dBm.
 
Problem 2:
Band 1 does not work at all, no signals present. If I switch to a Band 1 range like 4 GHz , 500MHz span the FREQ UNCAL appears and the unit becomes unresponsive.

Would you agree that a bad YTO could produce both of these problems?

and...
How on earth to you get access to the YTO ?
I can't see any easy access path, does the side PCB need to be removed along with the front panel?

Thanks
T.

 


 
MarkL:
It's possible the YTO could be at fault, but I wouldn't jump to that conclusion.

I would try to characterize the problems more, and one problem at a time.  Start with Band 0 since it's at least somewhat functional.  The first thing I would try is to look at the cal signal in Band 0 in zero-span mode.  Does the signal still drop in amplitude after 10 minutes?

If so, does the amplitude also drop on the video out?  Can you verify the YTO frequency and output level when it happens?  It may be good to verify the test frequencies and levels shown on the block diagram in the Assembly Level Service manual.

For access, I've found it easiest to remove the screws from the front panel, pull it forward, and remove the entire RF section and set it to the side with it still connected.  Be sure to remove the hard line SMA from the back of the input N connector.  It's easy to mangle the hard line when removing the front panel.

I don't recall if I needed to add a couple of SMA jumpers to work on the RF section when it's out of the chassis, or if the existing cables were long enough.  It's a big spaghetti mess of wires, but I don't know how else it could be done.  The fun part is getting it back in, so take lots of photos of how cables were routed.
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