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Registered Member #60240
Joined: Mon May 16 2016, 07:01PM
Location:
Posts: 304
Hello Tektronix friends
After turning on a Tektronix pulse generator 284:
and after a slight adjustment of tunneldiode bias (TD bias), a screw drive adjustment on the front panel, the fast pulse output is about 200 mV amplitude and about 65ps rise time, Oscilloscope is a 11402 with a Tek 11A72 with 1 GHz bandwidth: Abscissa 5us / div, ordinate 50mV / div
Abscissa 1ns / div, ordinate 50mV / div
After some time, a few minutes, the pulse is gone: Abscissa 2us / div, ordinate 50mV / div
Registered Member #2906
Joined: Sun Jun 06 2010, 02:20AM
Location: Dresden, Germany
Posts: 727
..few minutes... this is the order of magnitude where thermal effects happen. This can happen due to old caps on a power supply rail, bad heatsink contact (aged thermal compound), bad mechanical contacts (can worsen due to thermal expansion). Open the thing, observe the rails. Take a heatgun (temperature controlled!!) and point it at parts to see if it speeds up failure then use cold spray to try reversing the effect. Wiggle contacts and so on. I dont think your tuning has anything to do with this behavior. Its most likely that you just played around for long enough after/while tuning. If the tuning is however the problem, think about how tuning is done. If some component gets more current, check its sink and source obviously. Dont loose the screws while disassembly, its enough to loose warranty
Registered Member #60240
Joined: Mon May 16 2016, 07:01PM
Location:
Posts: 304
Now, images of the fast pulses of the working Tektronix pulse generator 284 with an 11403: 11A72 for fast pulse, white, below the trigger pulse, red, x-axis 10 μs / div, y-axis 100 mV / div, 5 ns lead time:
Above the whole fast pulse, white, below the trigger pulse, red, x-axis 200 ns / div, y-axis 50mV / div, 5 ns lead time:
Above the fast pulse, below the trigger pulse, x axis 20 ns / div, y axis 50mV / div, 5 ns lead time
Above the fast pulse, below the trigger pulse, x axis 10 ns / div, y axis 50mV / div, 75 ns lead time
Above the fast pulse, below the trigger pulse, x-axis 1 ns / div, y-axis 50mV / div, 5 ns lead time
Displayed rise time of the pulse with the 11403 less than 300 ps.
Registered Member #60240
Joined: Mon May 16 2016, 07:01PM
Location:
Posts: 304
An image of the fast pulse of a working Tektronix pulse generator 284 with a Tektronix TDS820 6GHz, 44 ps Rise time: x axis 50 ps / div, y axis 50 mV / div, 5 ns lead time:
An image of the fast pulse of a functioning Tektronix pulse generator 284 with a Tek TDS820 6GHz, 44 ps Rise time: x axis 20 ps / div, y-axis 50mV / div, 5ns lead time:
The displayed rise time of the pulse with the TDS 820 is less than 100 ps.
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Tektronix 284 pulse generator-problems with the fast pulse
