Author Topic: Agilent 8560E Repair  (Read 1021 times)

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Offline NHnewbieTopic starter

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Agilent 8560E Repair
« on: May 02, 2018, 07:24:47 pm »
I recently acquired a used Agilent 8560E in very good condition. It works as described in the initial checkout section of the user manual. I do see one possible issue, however. The alphanumeric characters on the screen vary in brightness, to the extent that some lines in a single character are brighter than others. Perfectly readable, but probably not supposed to look like this. Because this occurs at many positions on the screen, it doesnt seem to be a CRT issue, but maybe something in the character generator. Any suggestions as to where to begin looking?

 

Offline SaabFAN

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Re: Agilent 8560E Repair
« Reply #1 on: May 02, 2018, 08:48:53 pm »
Without looking at the service manual, I'd say there's a problem with the Video-RAM. It's losing the "bright/dark"-information.
Probably an SRAM-Chip that's gone bad.
Is the problem constant with temperature? Are the bright areas moving when the picture changes?

Another source of the problem could be one of the ROMs. If the device was build in the early 90s, they have reached their specified data-retention time. If they are socketed and you can find a firmware (preferably a newer one), rewrite the ROMs and see if the problem goes away.

If that doesn't help, the video subsystem is your next area to check.

Edit: It also could be something as simple as a cracked solder-joint on one of the SRAM-Pins that just barely transmits AC. Apply slight pressure to the processor-board or the RAM to see if the problem changes/goes away - That should be the first try.

Offline NHnewbieTopic starter

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Re: Agilent 8560E Repair
« Reply #2 on: May 02, 2018, 10:16:48 pm »
Thanks, SaabFan,

Will check all these possibilities out. No observed temp correlation.
 


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