HP-25 not working

[Peval]

Hi all,
I'm new in this forum so it could be I'm submitting something already discussed that I didn't find.
in any case, I own a very old HP-25 (1974 or 1975 I'm not sure).
I would like to resume it working.
it is not working by 40 years probably.
I do not remember what was the cause that force it to stop working.
Maybe a try to use it connected to the power supply but without batteries or maybe something else.
What I did, following some suggestion found on the net, was to remove the plastic "bridge" between batteries, remove the old rechargeable batteries and place two Alkaline AA instead.
Still not turns on.
I have read that in this case one of the possible problems could be the ACT chip.
I'm ready to buy from panamatik (http://www.panamatik.de/html/hp_calculat...r_kit.html) the repair kit.
But if there are some other possible reason why it does not turns on, please give some advice what to check and how.
Many thanks in advance for your help.
Best regards to all.
Peval