Tektronix 284 pulse generator, problems with the fast pulse

• Tektronix 284 pulse generator, problems with the fast pulse
  Posted by Physikfan on 04 Oct, 2017 09:22
• 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
  
  
  And this fast pulse does not come back!
  
  Who knows any advice?
  
  VG
  
  Physikfan
• #1 Reply
  Posted by Physikfan on 06 Oct, 2017 15:32
• Hello Tektronix friends
  
  I have found some interesting facts in the instruction manual of Tek 284:
  
  
  This means that mechanical stress at the output socket (GR878) may influence the electrical characteristics
  of the tunnel diode.
  
  
  And with the heating of the device after switching on one must change the tunnel diode bias.
  
  
  
  Trigger signal and fast pulse, about 200 mV amplitude and about 65ps Rise time:
  
  
  
  Regards
  
  Physikfan
• #2 Reply
  Posted by doktor pyta on 07 Oct, 2017 20:26
• It seems that front panel TD bias adjustment range is not sufficient. Inside there is R133 coarse TD bias potentiometer. Try to use it with front panel TD bias potentiometer centered. TD bias changes with temperature so it should be adjusted after warm-up time.
• #3 Reply
  Posted by Physikfan on 09 Oct, 2017 10:29
• Hi Doktor Pyta
  
  I will do it within my next free hours.
  
  In the mean time I have found an always working Tektronix pulse generator 284:
  
  The fast pulse, shown with a Tektronix 7904, plugin 7A29 for the fast pulse, plugin 7A19 for the trigger signal:
  
  Above the entire fast pulse, below the trigger pulse, x-axis 200 ns / div, y-axis 100mV / div:
  
  
  Above the fast pulse, below the trigger pulse, x axis 10 ns / div, y axis 100mV / div, 5 ns lead time (lead time)
  
  
  Above the fast pulse, below the trigger pulse, x-axis 10 ns / div, y-axis 100mV / div, 75 ns lead time
  
  
  Above the fast pulse, below the trigger pulse, x axis 5 ns / div, y axis 100mV / div, 5 ns lead time
  
  
  Above the fast pulse, below the trigger pulse, x axis 1 ns / div, y axis 100mV / div, 5 ns lead time
  
  
  Displayed rise time of the pulse is about 500 ps (Tek 7904).
  
  Regards
  
  Physikfan
• #4 Reply
  Posted by Physikfan on 13 Oct, 2017 09:32
• 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 ?s / 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.
  
  Regards
  
  Physikfan
  
  
• #5 Reply
  Posted by Physikfan on 14 Oct, 2017 22:04
• 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.