HP 41CX Halfnut CX EXT FCN missing

[HPnerd]

Hi all, maybe you can bring light in my problem:

i changed the backplane pcb due corrosion and missing lanes at my HP 41CX 2652Sxxxxx.
The donor of the backplane was a working CV 2818Sxxxxx (without the CX-addon pcb).
After changing the backplane the calculator was a nice "CV", okay i soldered the CX-addon pcb, a TIME 2C and CX TIME was added - but no EXT FCN nor a CX EXT FNC!
The additional catalogs 4,5 and 6 are missing as well...

So i did a rework of the ROM at the main pcb - now everything execpt the main pcb (same partnumber) was "CX" - but still the same - no ECT FCN nor CX EXT FCN nor catalogs...

Where the hell is the CX EXT FCN located at the Halfnunts?

Thank you for your answers, best regards from Austria
Walter

[BillBee]

This thread should help you.

https://www.hpmuseum.org/cgi-sys/cgiwrap...read=70045

3rd one.

-Bill

[HPnerd]

Thanks Bill,
You did make my day :-)
i did not loose any thought about the display-pcb to hold any ROM...
so i have to completly remove the key-pcb again to change the display-pcb :-( but i think it is worth to do so :-)
Thanks a lot for this value information, again best regrads from Austria
Walter