HP97 memory fault?

[Hans-Peter]

My 97er works in run mode without any trouble. The printer works also.
But the cardreader says on every card "Error". I fixed the transport spindle with the silicon tube but no luck. Then I wrote a program with a endless loop just for fun. After about 1-2 minutes the calc stops the program. Then when I switched to pgm mode the display shows the step 994. Back to run mode the calc works fine but the pgm mode was stuck. Pgm clear no chance. Power off, wait for a minute and the pgm mode was fine. But only for a short while.
A optical check of the CPU Board with the roms shows a slide black film over the silver legs of the roms, like my silver can in my livingroom. No corrosion like a battery drain.

Is there any chance to fix it without change the complete Mainboard?

   

Hans-Peter