Broken HP-41C (won't turn on)

[dpauw]

Dear forum members,

this is coming from a new member and absolute HP-41C beginner, so please forgive me for any stupid questions / wrong jargon, etc.

I have a HP-41C (square display edges, so "full nut"?).

The calculator was in a drawer for 15+ years and would not turn on. Upon opening it, it turned out that the battery contacts were corroded. Since then, I have taken the following steps to repair the unit:

• I got a new flex PCB from TheCalculatorStore and installed it.
• Cleaned all contacts and battery springs.
• The screw posts seem fine; nothing broken (yet).
• Replaced the capacitors C1 and C3 (they looked pretty blown up).
• Zebra strip does not look corroded and has (according to my multimeter) a clear electrical passage on all sections.
• I tried to install additional spacers around the lower screw posts to increase pressure on the zebra strip.
• When the unit is assembled, I measure around 5.5 V through the expansion ports (when battery is connected). The battery pack - fresh batteries - directly measures in at 6.1 V.
  

Still, the calculator seems dead.

The only reaction: When the batteries have been out for a while and I bring the top and bottom half of the calculator together, I get a short flicker of "hieroglyphs" in the top part of the display. So there seems to be some life left in it.

After that, it goes dead again and will not react to anything.

Does anybody have any idea what more I could try? It's been weeks now and I feel like I have tried any idea I could find on any related forum...

Thank you very much!

Yours,

Dominik