Re: HP-33E Parts


What you have stated would appear to be impossible. The On/off switch in the 33E (and all other 3xE models) has
3 cotnacts. In the 'off' position all 3 are disconnected, in the 'on' postion all 3 are connected. One of them goes to the +ve battery terminal (and also to the output of the diode/resistor charger). One of them goes to the +ve input of the PSU converter (and thus powers the machine). The last one goes
to the other side of the resistor in the charger circuit, so that this resistor is shorted out when the machine is on (it thus increases the current drawn from the AC adapter, which is then both powering the machine and charging the batteries).
The 3 wires in the battery-terminal flexiprint are ground, charger AC output (the other side of the the charger socket is grounded) and the battery +ve terminal (again, the -ver terminal is grounded).
Sionce the power input to the converter is not available on the flexiprint, there is no way you can make the machine power up by shorting connections here.
I would guess there's a short between the +ve input to the PSU and the connection to the charger resistor (either on the PSU flexiprint, the keyboard/logic board, or the switch contacts). The result is that the machin attempts to run from
the battery via this resistor even when the switch is off. The current available might not be enough to get the PSU (or CPU clock?) started (hence the display is dark when you first put the batteries in) but it will keep it going.

Possibly Related Threads...
Thread Author Replies Views Last Post
  HP 35S: Resistors in Series or Parallel (Portred from HP-33E) Eddie W. Shore 2 904 10-14-2013, 05:29 AM
Last Post: R. Pienne
  HP-97 Printer parts davorin 5 1,382 08-29-2013, 02:10 AM
Last Post: Benoit Maag
  Identify HP-01 Prototype parts aj04062 3 933 06-11-2013, 09:49 PM
Last Post: aj04062
  3D-printed calculator parts? John Ioannidis 13 2,258 05-24-2013, 12:32 PM
Last Post: Bruce Larrabee
  HP 39gii Tutorials Parts 1 and 2 up Eddie W. Shore 3 1,064 03-11-2013, 07:43 AM
Last Post: Herman T
  Interest in CNC parts? Hugh Evans 11 1,927 10-11-2012, 12:50 PM
Last Post: Hugh Evans
  Parts for WP-34s: What would you like to see? Hugh Evans 29 4,236 10-07-2012, 12:38 PM
Last Post: jerome ibanes
  Woodstock parts compatiability? Russell Dobson 7 1,530 03-28-2012, 05:35 AM
Last Post: Luiz C. Vieira (Brazil)
  WP34s Parts List Barry Reeves 21 3,297 02-03-2012, 11:39 PM
Last Post: Dominic Richens
  First four parts of the Beginner RPL Tutorial up Eddie W. Shore 4 1,012 10-07-2011, 12:58 PM
Last Post: Peter Murphy (Livermore)

Forum Jump: