HP-16C switch-on problem.


I have recently acquired a 16C from someone who had not used it for a long while. It functioned perfectly when I installed new batteries but after a few days would not switch on. I tried all the tricks in the manual and within the archives of this forum. Shorting the battery produced "Pr Error" when subsequently switched on, but it would not then switch off! If I leave the batteries out for a few days it will then work....but not for long and we go around the loop again. Battery voltage is fine and it passes all self-tests when working. However, I have noticed that when entering numbers quickly (esp. repeated digits), the input is sometimes interrupted by the memory status displaying but I don't know if this is normal.

Any suggestions would be appreciated especially since this 16C is in near-perfect condition. Thanks in anticipation.



I have seen this sort of symptom in an HP12C and the problem was that one of the IC's terminals had a soldering bad contact. After resoldering all terminals it worked fine till yesterday (I've been with its owner). More than 8 months are passed.

You're probably find someone that deals with Electronics in a way he'll be able to resolder the terminals and check if they are fine, unless you can do it yourself. If you are skilled in Electronics, you can open the calculator and you'll see two IC's: a big one right under the LCD and a smaller one, at the right side. You can unconditionaly resolder all terminals of both IC's, small amount of solder and low power soldering iron. I normally short batteries terminals (+ and -) and use the same wire to connect with the soldering iron metal parts (reduces ESD levels), even if it uses ceramic tip. Just take care not to heat up the terminals too much; also, you can reduce thermal effects by soldering even terminals first, then the odd ones (or the opposite). Wait for a while after each 8 terminals to cool up the IC package and get back on soldering the other 8.

You can print these tips and show them to the one that's going to do the job, if it's not you the one to do it.

Also, wait for other posts that can give you other solutions. Maybe I have missed something in your explanations and I'm trying an extreme solution.

I've done this with many HP calculators and they got back to normal operation.



Thanks Luiz. Info much appreciated. This is a last resort though. Graeme

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