HP-15C Not Powering On .... Mostly

[whirligig]

Hello Everyone,

I'm trying to power up a HP-15C that my wife inherited from her Dad. He received it new back in the mid 80's but never put it to use. I replaced the original batteries with some LR44's. There was no corrosion in the battery compartment but I did find some on the upper traces around the large chip. It's been removed and cleaned with denatured alcohol, Q-tips, and toothpicks. I was only able to power it up twice by shorting the battery terminals. In the photo, you'll see some symbols on the screen. What you don't see is that it is flashing when this occurs. In the other photo is the 1LH1-0306-85011 chip that I mentioned earlier. Note some of the pins have a dull look to it probably from the corrosion earlier. Right now I am frustrated trying to get this to power on. I've tried different key combinations e.g. ON & Y^x, ON & -, etc. but no joy. I am considering applying some solder flux the pins on the chip and reflowing the solder joints to see if this fixes the problem. What do you think?

   

   

[Dave Frederickson]

The chip looks like it still has some corrosion. Try starting with white vinegar to dissolve the corrosion. Then water to neutralize any acid left over from the vinegar. Then alcohol to final clean and help any left over water to evaporate. Dry with compressed air.

[whirligig]

(11-07-2021 06:35 PM)Dave Frederickson Wrote:  The chip looks like it still has some corrosion. Try starting with white vinegar to dissolve the corrosion. Then water to neutralize any acid left over from the vinegar. Then alcohol to final clean and help any left over water to evaporate. Dry with compressed air.

Thanks Dave, I followed your instructions. I can see that vinegar does a more thorough job than denatured alcohol. It's drying now then tomorrow we'll see.