Re: 2465 - impending U800 failure?


Bob Koller <testtech@...>
 

The first thing, always, is to check the power supply for voltage and ripple, and repair as required. But, the symptom you describe does sound like a failed U800, or, less likely, one of the horizontal deflection plate leads came off the CRT pin. Good Luck!


From: cmjones012003
To: TekScopes@...
Sent: Thursday, January 17, 2013 1:16 AM
Subject: [TekScopes] 2465 - impending U800 failure?

 
Hello all,

I haven't posted to this list in a long time but have just been lurking, I'm afraid.

One of my trusty 2465s has started to give trouble. It's serial number 102481. I bought it used, surplus about 10 years ago and it's had plenty of hard use since, being my daily workshop scope. I've never even undone the case screws - it's Just Worked, and stayed spot-on accurate. I think the tube is a bit tired, since the trace loses focus at high brightness and it's impossible to get the whole screen (corners and centre) exactly in focus at the same time, though it's always been like that and it's good enough.

Yesterday, I switched it on to use it, and it came up as usual but after a couple of minutes the entire display, readouts and all, suddenly jumped off the right hand side of the screen and stayed there. I could just about see the left hand end of the trace by winding the horizontal position all the way over to the left, and the scope was clearly still working otherwise: the bit of trace I could see responded to input signals and adjustments of the controls. I noticed also that pressing the 'beam find' button put the display back in the centre, but shrunken as I'd expect.

I tried the scope again a little later on and the display came back, but tried it again today and it worked for a few minutes then suddenly jumped off to the right again.

I do have the service manual for it, but before I start digging in, are these the typical symptoms of U800 failure? Searching the group, it seems that U800 failure tends to push the display to the left, and I haven't seen anyone document how 'beam find' behaves in that case.

Thank you in advance
Chris
Cambridge, UK

--
http://www.martin-jones.com/



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