Author Topic: Tektronix 465 Channel 2 issue  (Read 285 times)

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Offline 8bitmime

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Tektronix 465 Channel 2 issue
« on: September 23, 2020, 04:47:42 am »
Hello Everyone,

new to the forum but excited to be here. 

I recently purchase a Tektronix 465 oscilloscope, the price was right and it was in pretty good looking shape.  when I got it home though an plugged it in, channel 2 started to give me some issues.  Channel 1 is all fine and dandy but channel 2 gives me the behavior shown in the video below (its short but it gets the point across). 

I have already spent an hour or two google-ing the issue.  I started with "oscilloscope channel skipping" and didnt see anything similar to my results.  I tried "oscilloscope channel doubling" and "oscilloscope channel flashing" also to little effect.  Ive tried specifying the make / model as well to see if any other users with this machine have had similar issues and havent seen anything too promising. 

I have not yet torn the machine down and given it a good cleaning (I know this is always the first step), but I got it monday night and didnt have a chance to open it yesterday or today, i probably wont really get to open and clean it really good until this weekend. 

I wanted to post here and see if anyone has seen similar behavior from a machine.  At this point the only thing I have on the docket to try is giving it a really good cleaning to see if its just a bad contact somewhere, but im not sure if that is really the problem.  Ive never fixed an oscilloscope before but im no stranger to electrical projects.  Please forgive the vimeo link, i was unable to attatch my video directly to this message, it was too big. 

Link to video of my issue:  
Please forgive also the stupid video name, i forgot to name it when I uploaded it.

Thank you all for the advice in advance.   

Online med6753

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Re: Tektronix 465 Channel 2 issue
« Reply #1 on: September 23, 2020, 01:00:15 pm »
First, download a service manual if you haven't already. There are lots of sources out there.

A good cleaning first couldn't hurt.

Since channel 1 and 2 are identical on the Vertical Pre-amp board the best way to troubleshoot this is to apply an identical signal, such as the calibrator, to both channels and then probe each signal path until the issue is located. But that assumes you have another scope to trace it and I assume you don't. In that case you are limited to troubleshooting DC voltages only assuming you have a DMM. And you most likely won't narrow the issue down.

Can you borrow another scope from someone? Using another scope would be the quickest and most efficient way of tracking down the problem.
An old gray beard with an attitude.

Offline 8bitmime

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Re: Tektronix 465 Channel 2 issue
« Reply #2 on: September 23, 2020, 02:06:26 pm »
I do not have another scope and cant borrow one from anywhere at the current time.

Ive already downloaded the  manual and im reading it as time permits. 

Thank you for the suggestion, this weekend when I bust it open ill give the vertical preamp a visual inspection.  i wont be able to debug anything too seriously but I can always check for burnt components.   

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