Author Topic: Tektronix 475 twitching display  (Read 2994 times)

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Gazucha

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Re: Tektronix 475 twitching display
« Reply #25 on: February 23, 2019, 12:28:26 am »
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Forgive me Dave for I have sinned ...    :-DD

Or we could post selfies with a sign tied around our neck saying what we did.



 Priceless. This is...

 

Gazucha

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Re: Tektronix 475 twitching display
« Reply #26 on: February 23, 2019, 12:41:21 am »


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If you think the alternate triggering is not working as well as it should, then you could do the trigger calibration procedure in the service manual and check for excessive noise and ripple on the power supply outputs.

 Other than those two things, I would not mess with it for fear of damaging something for little gain.

Thank you again David.

Wise words.

I shall check out the trigger calibration but shall focus more on aesthetics. Bought some Letraset today for the panel buttons, and found the 'Tektronix blue' spray paint in a graffiti shop.

Need to also make some diy feet. Maybe I'll drill an alloy bar? Or we have super-hard wood here in Brazil.
 

Offline David Hess

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Re: Tektronix 475 twitching display
« Reply #27 on: February 23, 2019, 11:31:28 pm »
I shall check out the trigger calibration but shall focus more on aesthetics.

The tunnel diode based trigger circuits used in these oscilloscopes tend to drift a little over time compromising performance.  The trigger calibration procedure does not require any special test equipment and is easy enough so it is well worth doing if a problem is suspected.  If there is a real problem with the trigger circuit, then there is a good chance that the trigger calibration procedure will reveal it.

My notes say that all of the 475, 475A, and 485 models used tunnel diode based trigger circuits.  The 100MHz models like the late 464 and 466 and all of the 468 units used integrated triggers but I think at higher speeds it was easier for Tektronix to stay with the tunnel diodes.
 


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