I bougth a Casio PB 300 to an Ebayer from Montana, US. The machine arrived in perfect condition, just the computer and the soft case. I dont think it has been used, really. It looks new.
But one problem with these Casio (as well as with the FP12) are the rechargeable batteries. They are NI-CD and they are complete dead after 30 years. So I decided to replace them by a little Li-Po battery from a RC Helicopter, and use a USB cable as charging device. This is an easy one to do!
Here you can see the PB300 open. The white battery block is really 4 AAA NI-CD cells. They supply 4.8v. to the calculator when fully charger.
The next photo shows the Li-Po installed. It is just sticked with double side adhesive tape. It comes from a mini-helicopter. Attached to the battery there is a 3.7 to 5v. conversor. (easy and cheap to get from eBay). It provides a friendly 5v. to the Casio, and it also prevents the Li-Po from over discharging, as it will cut off current when battery voltage is below 3.3v.
The chargin lead from the Casio has been redirecte to the battery, as we will recharge it with a USB Charger (from the same RC Helicopter).
This is a more detailed photo: I writed down that the calculator was made in 1983, and the printing module in 1982. I had to replace the printer mechanism. There is an explanation about this in another article.
The perfomance of the new battery is incredible. I have spend several rolls of paper, and still holds charge. Charging from USB takes about 25 min. There is a photo of the modified RC Helicopter charger here.It was not difficult to find a charging plug in the local electronics store. The USB cable has a charging circuit inside, it will stop charging and light a led when the Li-Po is charged.
Aditionally, with the new battery the PB300 us extra - light.
And here, you can see the result!
