My original HP-25, ailing

[John Garza (3665)]

I definitely agree with Teenix. Better to keep it even if you don't have an immediate solution.

You would be surprised what corrosion can do.
Ensure your contacts are scrupulously clean, then use full strength deoxit.
When a battery or corrosion is suspect NEVER use the AC charger.
In fact, it's good policy to never use the charger and always charge the batteries externally, just in case.

If it's not corrosion, it will likely need a new chip from a donor machine or a Panamatik upgrade.

I was in a similar situation a while back. I had an HP-29C that would not take a program. I installed a RAM chip from a donor HP-25C. Then I installed a Panamatik in the HP-25C. Both are working fine now.

To Disassemble:
remove battery
remove two top rubber feet by inserting a small (little greenie) flatblade screwdriver to pry them up.
unscrew the screws that were hidden under the feet.
press on one of the charger contacts with the screwdriver to move the keyboard away from the bottom. Gently pry the halves apart.

Check for noise on the power supply (bad capacitor)
And check the timing signals as per the Panamatik docs.

Access to the keyboard can take 1 of 2 paths:
1: If you can see holes in the back of the keyboard that is the easy path
Spray deoxit in the holes and scrub with some fine stranded copper wire in each hole. Flush any debris out with spray deoxit, Let dry.
2: No holes requires you to shave off the tops of all the little heat stakes.
Then scrub under the metal ribbon strips with deoxit and a homemade plastic or cardstock tool as described in Teenix's doc. Reassembly will need Gorilla glue (the type needing water to activate). Lay the keyboard back on the faceplate with the heat stakes lined up in the holes. Drop of water on each stake, then Gorilla glue, then spread it around in a little circle about 2mm diameter with a toothpick. Do this for each heatstake. Let it dry overnight. This duplicates the 'mushroom top' of the original heatstakes and is very strong. The water activated glue expands during the curing process to make the wide top.

Also, while you have the keyboard apart, clean and re-lube the slide switches with silicone grease.

Good luck !

-J