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

[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]

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

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.

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

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

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.

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

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.

  This might be working because it is intensifying - not sure without more testing.

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.

That will need to be fixed.  You may damage something inside the scope if you let it overheat.

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.

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.

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.

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

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

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?

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

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.

Try http://bama.edebris.com/manuals/tek/465%282%29/

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?)

[drappehs125]

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.

I know how the lights work. I can get both to come on on channel b but neither will light with the probe in channel a.

I have followed instructions to set the delayed sweep but the only thing that happens is the CRT sketches out sometimes.

I forget that this thing is 30 - 40 years old. 'No Storage' is unimaginable to me - It was built before I existed.

[dfmischler]

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?

Maybe.  I can set up a display on my 475A for which both the high and low parts of the trigger view are off the display, but it would be an unusual coincidence if you did that by accident.  Try playing with the trigger level while pressing trigger view and see if you can see anything.  Yours might be broken.

[drappehs125]

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?

Maybe.  I can set up a display on my 475A for which both the high and low parts of the trigger view are off the display, but it would be an unusual coincidence if you did that by accident.  Try playing with the trigger level while pressing trigger view and see if you can see anything.  Yours might be broken.

Regardless of the trigger level I see nothing. It must be busted. I'm gonna crack into this tomorrow and poke around.

[dfmischler]

OK.  Let's try playing with the A & B triggers.  Set the B trigger source to "Starts After Delay", and coupling to DC, and set the horizontal mode to "A INTEN".  This should brighten the trace.  When you pull the sweep speed knob and click it forward one stop only half the trace should be brightened.  Now changing the delay time knob should move the bright part of the trace.

[drappehs125]

OK.  Let's try playing with the A & B triggers.  Set the B trigger source to "Starts After Delay", and coupling to DC, and set the horizontal mode to "A INTEN".  This should brighten the trace.  When you pull the sweep speed knob and click it forward one stop only half the trace should be brightened.  Now changing the delay time knob should move the bright part of the trace.

Yes confirmed.

I was misinterpreting the manual... Half the display has a different sweep rate - not separate channels. It seems to be working fine.

[dfmischler]

OK.  Let's try playing with the A & B triggers.  Set the B trigger source to "Starts After Delay", and coupling to DC, and set the horizontal mode to "A INTEN".  This should brighten the trace.  When you pull the sweep speed knob and click it forward one stop only half the trace should be brightened.  Now changing the delay time knob should move the bright part of the trace.

Yes confirmed.

Now if you switch the horizontal mode to "B DLY'D" you should see the part that was intensified in "A INTEN" expanded horizontally to fill the whole screen and sweeping the delay time knob should let you walk through the waveform.

[drappehs125]

Yeah that works as well. I am following steps in the manual I have now and it all seems to be working fine. The only problem that remains is the TRIG VIEW - I'm still confident I will get it working.

Thanks everybody who helped with this - this is the first time I have had the chance to work with an analog scope and I have learned a lot already.

[dfmischler]

An earlier 465 service manual is at http://bama.edebris.com/manuals/tek/465/

[dfmischler]

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

Yes.  At my first job where I used an oscilloscope they had one of those cameras.

[echen1024]

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.

Well, this is NOT a storage scope, so I think your definition is a little off there.

[dfmischler]

Well, this is NOT a storage scope, so I think your definition is a little off their.

The button is actually labeled "SNGL SWP".

[drappehs125]

Just an update on this scope - I have confirmed that all the horizontal functions work exactly as documented. The CRT does display random artifacts on varying sections of the screen while in B trigger delayed mode and seem to get worse/better if I play with that button... it may just need a little cleaning.

The trig view, however is still not functioning. I did manage to view something while holding the trig view and beam finder. I just get a horizontal trace near the bottom of the display and this does not change regardless of any other knob / button on the scope... See pic below.