Author Topic: HP 3585A CRT Twitch  (Read 295 times)

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Offline MarshallPlexiTopic starter

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HP 3585A CRT Twitch
« on: October 16, 2024, 07:28:24 pm »
Afternoon all!


I've had this HP 3585A for a few weeks now and it's been working great. Tonight I noticed that the CRT is, for lack of a better term, twitching. I took a video and you can see it more clearly once I turn down the CRT intensity later in the video. Also note the reference line is not as pure as it once was. It's almost striped looking now. 




Any idea what could be causing this? I would assume a power supply issue.
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Offline Grandchuck

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Re: HP 3585A CRT Twitch
« Reply #1 on: October 17, 2024, 03:44:39 pm »
Can you open it up and look at the power rails with an oscilloscope?
 

Offline KE5FX

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Re: HP 3585A CRT Twitch
« Reply #2 on: October 17, 2024, 11:32:52 pm »
Doesn't look too bad.  After checking the power rails and any electrolytic caps in the vicinity, you might try pre-emptively replacing all of the high-value carbon comp resistors in the focus chain and elsewhere.  They are prone to drift and noise as they age, sometimes in ways that aren't apparent when tested at low voltages with an ohmmeter. 
 


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