#170 Tektronix 465 review and troubleshoot Part 1

[Radio Tech]

I finally got my own Tektronix 465 oscilloscope. I have been searching for many years to get one that I could work on and get back running.
This unit was giving to me from a anonymous viewer.

I am going to do a series on repairing and aligning this old piece of Tek history.

[Radio Tech]

This is a bit interesting.
After just playing around with the controls I got the below waveform.
In channel 1 or channel 2 mode separately I only get a dot on the crt.
When pressing both channel 1 and 2 together I get a trace.
It is only control by channel 1 volts/division. Channel 2 has no effect.

I may should had put this video on the repair forum.

[AF6LJ]

This should be a good thread, lots of Tek 46x fan-boys and fan-girls out there.

With that waveform from the calibrator on the screen, when you push the trigger view button and rotate the A timebase trigger level what do you see???
If you see the normal trace and can move its position on the CRT at least you know most everything on the left side of the CRT is okay.

[bd139]

Sounds like the channel switch array is dirty. You can give it a squirt with switch cleaner from the top. Had similar trouble on my 465.

[Radio Tech]

This should be a good thread, lots of Tek 46x fan-boys and fan-girls out there.

With that waveform from the calibrator on the screen, when you push the trigger view button and rotate the A timebase trigger level what do you see???
If you see the normal trace and can move its position on the CRT at least you know most everything on the left side of the CRT is okay.

Agreed, these are fantastic old scopes.
Yes I can move it around bt doing what you asked.
Found a few more interesting issues while working on the scope.
I have had several emails, and messages stating I have the trigger mode set wrong. I do agree with that but it is the only way I could get anything on the display.

I will be posting some screenshots later today of the progress and working on part 2 of the repair.

[Radio Tech]

Sounds like the channel switch array is dirty. You can give it a squirt with switch cleaner from the top. Had similar trouble on my 465.

This is something I have not done yet and was waiting to finish part 2 of the video.
I do believe that some of the problems are in dirty contacts and controls.

[Radio Tech]

Here is a few screenshots of current state.  On the trigger board I found a diode that was cracked. It is D517. I looked up the Tektronix part number but could only find it was a signal diode.






I just removed it and tacked in a 4148 for testing.




As you can now see I have trace on channel 1 with the trigger mode set to auto.





Channel 2 as well.





I now have the probe attached and this is the resulting wave form.  Either sweep or trigger issue.






I can grab the time base or any other control on the right side of the scope.





As soon as I turn or push I loose trace.



Really does not matter what control I play with on the right hand side I will loose trace. Perhaps it is time to remove boards and give the controls a good cleaning.

Also wanted to add that turning the unit off then back on restores the trace. Trigger knobs also have no effect.

[AF6LJ]

Cool, progress.

[Radio Tech]

Cool, progress.

Thanks.

There  is more.
I pulled the trigger/sweep boards and cleaned the switch contacts. 
Then removed the cover from the time base cam and cleaned all the contacts.

I put the unit back together and tested it.

I can now get trace on channels 1 and 2 using the calibrator.





So this is better progress than I thought.
Still at times the trace will vanish.
It is also unstable.

[AF6LJ]

So it looks like, at this point you are left with just a few fussy controls to deal with.

[tautech]

I may should had put this video on the repair forum.

You still can !

For you as the OP, there's a button/icon at the bottom left of the page called Move Topic, use it !

All about this feature here:
https://www.eevblog.com/forum/blog/what_s-this-move-topic-icon-all-about/

[Radio Tech]

So it looks like, at this point you are left with just a few fussy controls to deal with.

Looks like that may do it. I have to order the caps to replace the ones needed. May even replace those tantalums also.
But it is good to see life come back in this old classic.

[Radio Tech]

I may should had put this video on the repair forum.

You still can !

For you as the OP, there's a button/icon at the bottom left of the page called Move Topic, use it !

All about this feature here:
https://www.eevblog.com/forum/blog/what_s-this-move-topic-icon-all-about/

Cool! 
I did not know this was a user feature in this board.
Thanks

[Old Printer]

As soon as I turn or push I loose trace.



Really does not matter what control I play with on the right hand side I will loose trace. Perhaps it is time to remove boards and give the controls a good cleaning.

Also wanted to add that turning the unit off then back on restores the trace. Trigger knobs also have no effect.

Are the right side controls that blank the trace mounted to the same board? If touching any of them have the same effect, it sounds like a broken trace/cracked solder joint etc. Either somewhere on the board, or a place where the board makes a connection to something else. I would guess that pressure on the board in different places is disturbing an intermittent connection or cracked joint. I have a nice 475, but have not been in it for some time so I don't recall the right side board setup.

[AF6LJ]

So it looks like, at this point you are left with just a few fussy controls to deal with.

Looks like that may do it. I have to order the caps to replace the ones needed. May even replace those tantalums also.
But it is good to see life come back in this old classic.

Good deal.

[Radio Tech]

Are the right side controls that blank the trace mounted to the same board? If touching any of them have the same effect, it sounds like a broken trace/cracked solder joint etc. Either somewhere on the board, or a place where the board makes a connection to something else. I would guess that pressure on the board in different places is disturbing an intermittent connection or cracked joint. I have a nice 475, but have not been in it for some time so I don't recall the right side board setup.

Yes there are many connections between the trigger / sweep board to the time base board. All the connections run through the main pcb via connectors.
See pictures of what I am finding on these connectors and the solder on the trigger l sweep board.

[AF6LJ]

Someone has been in there, and left a level 1.5 mess.

[bd139]

Looks like “someone was asleep at the tek factory” to me. I’ve seen that a couple of times. Even forgotten solder joints.

[Radio Tech]

I think you both are correct lol.

I pulled the A trigger hold off  control out. Took it apart. This is a dual function switch, Rear is a dual switch. Front is a variable resistor.  I was able to  clean the switch with some DeoxIt. How ever the variable part is sealed.  So drilled a very small hole into the body and was able to inject some D100L into it with a needle.

Put it back together and things are working much better. I still have the trace fade away issue but noticed something else. When connecting  a probe to the unit the display would blank. Turn it off and back on restores trace. Even a jumper just touching the outer shell of the jack will cause this. Sounds like a faulty ground somewhere. More digging to do.

A moment ago I was able to connect a function gen to channel one and 2.  After watching for a moment I saw the traces flicker. Bright, dim, then out and come back.  I also noticed the lights in the volts per division dim down.  More power supply issues also.

So the saga continues. I am happy to see it work when it does. I have recorded most of this on video.

[Radio Tech]

So here is a question for you 465 guru's.

I pressed the trigger view switch and only notice the rear set of contacts open.
The front set remains closed all the time.
Is this normal and only works in certain models? Or is the switch broken in a way?
I am searching through the manual to see if I can find the drawing of this.

[bd139]

Front set are bandwidth limit. Pull the trig view control out and it should open the front set.

[AF6LJ]

Yup....

[Radio Tech]

DUH.
Had a Homer Simpson moment. 
Yep that did the trick.

Got to clean those now.

Anyway thanks.

Still thinking I have a ground issue in the 5 volt area. I really need to get to some other things today but the curiosity is killing me.

[bd139]

Always worth tightening up all the mounting screws on the 465. Surprising number of weird things can be cured with that simple step.

[PartialDischarge]

I had one of these with a fault stored for a long time. Saw this thread and decided to give it a last chance. In my case the problem was the filtering cap for the +5V line, a 5000uF 25V cap. These seem pretty low quality electrolytics. Found laying around a couple of 50V 2200uF and put them in parallel.

That made it, working fine now.