Re: tempest PCB only some vectors shaky

Since you got no on-list response. I’ll throw my 0.02 in... having never worked on a Tempest PCB... please keep in mind I may be way off base.

Your pictures scream noise to me. I’d be looking to decoupling caps near the red line’s main ICs. Maybe the DAC and the TL082s.
Any electrolytic caps in the “red section” which might be in need of a recaping?

John

From: Joey Oravec
Sent: Monday, June 04, 2012 6:21 PM
To: vectorlist@vectorlist.org
Subject: VECTOR: tempest PCB only some vectors shaky
Howdy -

I'm trying to figure out why some, but not all, of the lines are shaky on my Tempest PCB. I set my oscilloscope to XY-mode with 1 sec persist and captured a screenshot. I'm not sure if it's allowed to send an attachment to the list, so here's a link:

https://picasaweb.google.com/lh/photo/CYke3MLZ4e94Cf5vb2UUPkuaTiHWm12LLNxmPUaffgU?feat=directlink

This is one corner of the diagonal line + alphabet self-test. Notice the blue line is solid but the red line is quite noisy. Predictably on the XY monitor the blue line is rock solid but the red line is shaky.

I've already replaced the TL082s just in case. I don't suspect the DACs since the lines are both in the same corner and I'm not seeing stair-step error. Does anybody else have a theory of what makes those two lines different, and why one might be rock solid and the other one shaky?

-joey
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Received on Wed Jun 6 02:00:39 2012