Hp-28S Does not Turn On


I recently cleaned my HP-28 taking care not to get too wet (used damp cloth etc).

Now when I install the batteries, all that I get is a slightly dimmed screen when I press on. No combination of keys that I have done so far has reset it.

An suggestions?




The 50g as well as the 48 series are IMHO overwhelming with to many functions and menues. In college many mates had the 48SX while I prefered the 28s because of a more straight forward approach. Today I have both calculators, but still I am a lot faster on my 28s. But the lack of I/O is of course a problem.


If the screen appears to get power and darken just slightly, but nothing is displayed, it may be a stuck key. I have a 32s that did the same thing, and was able to fix it.

Also, you've tried adjusting the contrast already, right? (Hold On, press + or -.)


Tried to find stuck keys, can't find one.

Interestingly, On - or + DOES ALTER the contrast.


That means that the processor is running correctly.


This will sound obvious, but make sure you put the batteries in right. I once had my 48g doing some very weird things, turned out I had reversed one of the batteries.


I did and did not make that mistake.


Tried another set of batteries? (just because they came new out of a packet doesn't always mean they're good).


I've tried several sets that work okay in my 41. I'll buy a new set and try them out.


I was more thinking a dead cell, but if they work OK in the 41 then there's probably some other reason for not working.

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