I have an HP-11c and changed the batteries but the only thing that happens is there are some numbers in the display that never go away. Yes, I tried all the button combinations listed in the manual. I even tried shorting the battery as described in the manual, still no luck. Any assistance would be apprecicated. If it is determined that mine is dead I would be looking for an 11c that has a dead display, since mine is ok.
You should short the battery contacts for some seconds and then let the 11C rest. You can also try to shorten them more than once before inserting the batteries.
I'd also test, if the new batteries are o.k. Do you have a meter ?
A friend of mine had a 71B with similar symptoms and he had to leave it for abt 2 weeks until it wanted to work again.
I hope you didn't try the reverse polarity with the batteries...
If you did everything right, I'm sure, that it isn't defunct.
Thanks for the tip, you are right, after shorting the battery about 3 weeks ago and leaving them out of the unit, it now works! I picked it up this morning, just for the heck of it, put in the batteries and it worked! Thanks