Electronics > Repair

Tektronix 465 (Mostly) Functional ... Possible Repair?

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drappehs125:
Hello everybody. I've just picked up a Tektronix 465. It has a calibration sticker from February of 1979 - awesome. It has serial number B062673, which is older than most others I have noticed poking around online.

I turned the thing and and what do you know, the damn thing works. Extremely bright display - both channels displaying voltage and frequency accurately (well, obviously out of cal accurate). It wasn't long before I started noticing problems.

1. All 'Uncal' lights are lit. No problem - I can just calibrate it.

2. The x1 and x10 lights on channel one volts/div knob are blown. No problem - I can replace them.

3. Pressing the 'TRIG VIEW' button does nothing but completely turn off the display. No beam is displayed whatsoever when this button is held.

4. Single shot capture mode also turns off the display. I can see that it actually does trigger and the waveform flashes on the screen for a fraction of a second.

5. The time base is always the same and the delay functions do not work at all. I have set the horizontal display to mix and pulled the time/div knob to change the horizontal base but both channels remain the same. Also setting the delay on channel b also does not work at all. Basically the only thing that works with regards to the horizontal function is the Time/Div knob when the knobs are locked. While trying all these different settings, something strange happens to the display... certain sections of the waveform displayed will be more intense than the other - and the position of the more intense section shifts depending on the combination of buttons.

6. If that is a fan I see through the back (I don't know what else it could be) - it definitely is not working.



I've only been looking at this scope for a matter of hours so there may be other things I find. I am looking for a service manual and a schematic.

If anybody out there has had some experience with this or a similar scope and have some helpful advice that would be much appreciated.

dfmischler:

--- Quote from: drappehs125 on August 09, 2013, 12:47:36 am ---1. All 'Uncal' lights are lit. No problem - I can just calibrate it.
--- End quote ---
All those lights mean is that the "VAR" knobs are not in the detents at the full clockwise position.  Or, the switches at those positions need help.


--- Quote ---3. Pressing the 'TRIG VIEW' button does nothing but completely turn off the display. No beam is displayed whatsoever when this button is held.
--- End quote ---
This will display the trigger waveform which might not be visible if the trigger level is too far off.


--- Quote ---4. Single shot capture mode also turns off the display. I can see that it actually does trigger and the waveform flashes on the screen for a fraction of a second.
--- End quote ---
That is what it is supposed to do.  Trigger once, sweep once, and that's it.


--- Quote ---5. The time base is always the same and the delay functions do not work at all. I have set the horizontal display to mix and pulled the time/div knob to change the horizontal base but both channels remain the same. Also setting the delay on channel b also does not work at all. Basically the only thing that works with regards to the horizontal function is the Time/Div knob when the knobs are locked. While trying all these different settings, something strange happens to the display... certain sections of the waveform displayed will be more intense than the other - and the position of the more intense section shifts depending on the combination of buttons.
--- End quote ---
  This might be working because it is intensifying - not sure without more testing.


--- Quote ---6. If that is a fan I see through the back (I don't know what else it could be) - it definitely is not working.
--- End quote ---
That will need to be fixed.  You may damage something inside the scope if you let it overheat.


--- Quote ---I've only been looking at this scope for a matter of hours so there may be other things I find. I am looking for a service manual and a schematic.
--- End quote ---
Try http://bama.edebris.com/manuals/tek/465%282%29/

PaulAm:
The x1 and x10 lights on the vertical channels will be turned on when

a) that channel is selected and
b) a probe with the right type of bnc is plugged in.  If you plug in a x10 probe with the readout pin, the correct scale light will come on.

The delayed sweep is complicated enough that you may think things are not working correctly.  Check on youtube for Tektronix and "delayed sweep".  There are a couple of good videos that show how that's supposed to work.  Generally you will have the H display set in A lock for normal work.

It's not a storage scope; if you have it in single sweep and a fast time/div setting you may not even see the beam.

drappehs125:
Thanks for the quick reply.



--- Quote ---All those lights mean is that the "VAR" knobs are not in the detents at the full clockwise position.  Or, the switches at those positions need help.
--- End quote ---

Yeah I feel stupid now. They are now fully clockwise and the lights are off.



--- Quote ---This will display the trigger waveform which might not be visible if the trigger level is too far off.
--- End quote ---

If I am triggering a signal and I can see the full signal voltage on the CRT wouldn't the trigger level be in view? Am I interpreting this wrong?



--- Quote ---That is what it is supposed to do.  Trigger once, sweep once, and that's it.
--- End quote ---

This is the first time I have used an analog scope. I'm used to the single trigger actually freezing the image on the screen.


--- Quote ---Try http://bama.edebris.com/manuals/tek/465%282%29/
--- End quote ---

This is for SN B25000 and up... mine is B062673. It will still be useful though.




SArepairman:
whats the point of a single shot like that? For a scope camera (that you put over the CRT?)

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