Re: Weak 9872CT Plotter Platen

Martin Hepperle
 

Here are some more measurements. 
 
Using my simple Uni-T 61B, max. 600V, 10MΩ impedance
measurements against ground (cathode of CR102)
  • cathode of CR103:   +474V
  • anode of CR102,102: -288V
  • anode of CR101:     -465V
  • calculated: from cathode CR103 to anode CR 101: +474V - (-465V) = 939V
  • before L101: 34.7V
  • behind L101: 34.0V
 
 
Using HP 3456A, max. 1000V, 10MΩ impedance
  • across cathode of CR103 to anode of CR101: 934V
    [that is: before passing through R105+R106, R102+R103 (1.8 MOhm each)]
  • across J101 (platen connected): 533V
  • across J101 (platen disconnected): 514V
    [that is: after passing through R105+R106, R102+R103 (1.8 MOhm each)]
 

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