Fullnut 41CX problems



I am trying to repair a Fullnut 41CX for Peter. Apparently, it had contact problems, but Peter said the batteries went hot after switching it on. This 41CX has a logic board similar to the 41Cs, and when I opend the Calculator, this logic board was out of its usual position. This may explain why the Batteries went hot, as it may have sorted some connections.

After cleaning the contacts and fixing the logic board in its normal position, I switched the calc on, but the display just showed "@@@@@@@@@@@@", and the beeper hummed.

I traced some signals with an oscilloscope, an found that the DATA,phi1 and phi2-signals were present though with an amplitude of about 1.7 V. The signals on pin 12 (LCD) was pure noise, so were Pins 6,7 and 8 (LCDC1,LCDC2,LCDC3). Pin 2 (ISA) showed some signals, but also carried a lot of noise.

Did anyone have similar problems or does someone know a cause/solution?

Thank you! Klaus

Possibly Related Threads...
Thread Author Replies Views Last Post
  Faulty fullnut 41CV Paolo Cipollone 5 1,370 09-07-2012, 04:59 PM
Last Post: BobVA
  Faulty fullnut 41CV Paolo Cipollone 3 954 08-25-2012, 09:50 AM
Last Post: Luiz C. Vieira (Brazil)
  41CV Fullnut shows "Memory Lost" consantly John Robinson 7 1,632 05-27-2011, 05:51 PM
Last Post: John Robinson
  Production Dates HP41CX Fullnut vs. Halfnut Frido Bohn 5 1,213 10-10-2010, 12:59 PM
Last Post: Jim L (OHIO)
  fix an HP 41C tall key - fullnut Damien MATTEI 6 1,252 10-14-2008, 11:22 AM
Last Post: Damien MATTEI
  Fullnut/Halfnut, what do I keep? Egan Ford 6 1,301 04-05-2008, 06:46 AM
Last Post: Massimo Gnerucci (Italy)
  HP-41C* Halfnut vs Fullnut Todd Popovich 13 2,717 07-25-2006, 12:24 PM
Last Post: Dia C. Tran
  41CX serial #'s -- halfnut/fullnut Karl Schneider 1 607 03-03-2005, 01:54 AM
Last Post: Raymond Del Tondo
  Replacing the CPU board on fullnut HP41 Vassilis Prevelakis 1 573 11-04-2003, 12:01 AM
Last Post: Dave
  HP-41CX fullnut noise!!! Michel Beaulieu 7 1,322 10-22-2003, 04:50 AM
Last Post: Victor Koechli

Forum Jump: