Re: 2465 help to fix


 

I can attest to the need for a bench fan when running this scope without a case.  I use a small clip on fan that can be pointed directly at the instrument.

My first thought for this problem was tht one of the Horiz leads was loose from the scope.  They are accessible from the bottom when the case is removed.  But then I saw the trace can be moved to the left side of the screen.  This seems to say the horiz is working.

I still lean to the idea that something is bleeding the power when knobs are turned but I cant think how since it didn't show when the OP measured voltages as he turned pots.

Im stumped.  Not quitting, just stumped.

From: Don Black
To: TekScopes@...
Sent: Sunday, January 12, 2014 2:36 AM
Subject: Re: [TekScopes] Re: 2465 help to fix

 
Have you tried tapping the instrument (gently) to see if it's sensitive to vibration. I think it would have to be very touchy to get these results from the mere vibration of turning a knob but it just seems so general that it's possible. While it could be the CRT it doesn't look like it to me so don't slash your wrists just yet. I've never worked on one of these but is it possible to measure the deflection voltage going to the tube. You should be able to see it jumping all over the place in sympathy with the trace movement.
At least you've won weird fault of the month award.

Don Black.
PS can someone advise if this model overheats if operated with the covers off and needs a desk fan blowing into it while working on it?

On 12-Jan-14 6:47 PM, machine guy wrote:
 
I have never seen anything like that.  You are able to put the trace nearly anywhere on the screen but it is usually right of center.  The trace that shows in the video looks like the cursor from the readout board.

The fact that you can position the trace right or left, mostly right, seems to say the U800 is working (but not necessarily right).  I am bewildered but will think about it and post back.

Perhaps someone with more experience on these will be better help to you.

Mac
From: max t mailto:maxxim_66@...
To: TekScopes@...
Sent: Sunday, January 12, 2014 12:24 AM
Subject: [TekScopes] Re: 2465 help to fix

 
Values on those pins is fine , about R352 levels from -4.97v to +4.97v
and R351 from 0v to +4.98v , looking the schematic seems to be ok ,
i have upload a new video with more details of scope rotating pots

this the video
http://www.youtube.com/watch?v=QaHsLDqqg4k&feature=youtu.be

regarding corrosions ..the scope is very clean there no traces
of that i have changed all electrolitics but they was almost
fine maybe the c1022 with broken terminal it was defective
or while assembled too much forced or manipulated then with age
disconnected.

--- In TekScopes@..., machine guy mailto:machineguy59@... wrote:
>
> I have not seen this problem before but we can trace the schematic.  My next measurements would be to see if the voltage at pin2 of R352 changes as you turn the intensity and pin 2 of R351 changes as you turn Readout intensity.
>
> But it is concerning that changing settings on the panel (vert pos, etc) changes the horizontal left and right.  That may indicate a bad CRT tube.  I am sure there are other measurements to verify that and perhaps others on the forum will have ideas here. 
>
> For now, I would trace the schematic and check voltages beginning at the intensity knobs. 
>
>
> ________________________________
> From: max t mailto:maxxim_66@...
> To: TekScopes@...
> Sent: Saturday, January 11, 2014 12:19 PM
> Subject: [TekScopes] Re: 2465 help to fix






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