Author Topic: Display top line cut off on HP 8591EM spectrum analyzer  (Read 687 times)

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Offline yanko

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Display top line cut off on HP 8591EM spectrum analyzer
« on: February 02, 2018, 04:34:23 pm »
I have a HP 8591EM EMC analyzer. The top half of the top line of the display is cut off making it impossible to read out results. (Photo attached) Basically, several pixel rows are missing.

Before I get too deep into trying to fix this, I'm wondering if this is something that has to do with CRT vertical size/position that can be fixed by tweaking a pot, or is it a problem with whichever module is generating the video signal? If the latter, is it likely to be an easy fix?

There are menu options that move the display in the vertical direction, but don't change how many pixel rows are displayed.

Thanks!
Yanko
 

Offline cvanc

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Re: Display top line cut off on HP 8591EM spectrum analyzer
« Reply #1 on: February 02, 2018, 05:11:47 pm »
I'm not familiar with the 8591 but if the display is a CRT as you say, the image size is entirely controlled by the scan/deflection system of the CRT.

There may or may not be simple internal adjustments for image height and width - hopefully someone who knows this unit well will comment.

Good luck getting it sorted out.
 

Online Tomorokoshi

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Re: Display top line cut off on HP 8591EM spectrum analyzer
« Reply #2 on: February 02, 2018, 06:15:59 pm »
Not sure if there is a subtle difference but in the 8590C service manual:

https://www.keysight.com/upload/cmc_upload/All/08590-90316.pdf

Starting on page 33 there are detailed procedures for adjusting the display.
 

Offline yanko

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Re: Display top line cut off on HP 8591EM spectrum analyzer
« Reply #3 on: February 02, 2018, 06:52:16 pm »
Thanks for the replies. I actually already tried the adjustment procedure in the service manual. It only moves the image up and down within the screen but does not change the contents of the image.
Also, based on my limited understanding of CRT monitors, changing the vertical size or position can only help if the issue is caused by the image falling out of the physical constraints of the CRT, which is not the case here. Not knowing the details, it feels that this can be caused by the vertical SYNC pulse not lining up with the video signal, but I was wondering if anyone has seen this same issue before. Maybe the sync signal timing is adjustable somehow?
Yanko
 

Offline MarkL

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Re: Display top line cut off on HP 8591EM spectrum analyzer
« Reply #4 on: February 06, 2018, 05:03:44 pm »
There also the time/date one line above the "hp" logo which is totally off the screen.

Check that both your SYNC settings are set to NRM.  It can cause this exact problem.  It is on page 3 in the CONFIG menu.

 

Offline yanko

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Re: Display top line cut off on HP 8591EM spectrum analyzer
« Reply #5 on: February 06, 2018, 06:40:41 pm »
This was it! Thank you, MarkL.
I'm very glad I hadn't yet opened it and tried to mess with the video module!
 


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