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From: ehsjr <ehsjr@verizon.net>
Newsgroups: sci.electronics.repair
Subject: Re: CRT Display Fault
Date: Wed, 18 Jun 2025 16:07:05 -0400
Organization: A noiseless patient Spider
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On 6/18/2025 1:11 PM, Cursitor Doom wrote:
> Gentlemen,
> 
> I have a spectrum analyzer with a display problem. Forget the precise
> make and model for once; this is a common display issue affecting
> *all* CRT displays. Let me describe what I'm seeing...
> At first switch-on, there's no picture at all; just an elongated,
> fuzzy blob on the screen. Over the course of the next few minutes,
> this fuzzy blog gradually expands and reveals the image it should
> display. However, this image, even after an hour or more, never gets
> beyond about a third of the size it should be. I can make out what
> it's *trying* to display; all the information is present there, but
> it's compressed and fuzzy (and a bit twitchy as well).
> I'm sure I've encountered this issue with CRTs many times over the
> past 60 years, but I'll be f***ed if I can remember what causes it.
> Any ideas?
> 
> CD.

Could be a high voltage supply problem,
maybe a leaky HV capacitor.

Generic Troubleshooting:
Rule 1: Check the voltages.
Rule 2: See rule 1

Ed