Commodore SR4148R restoration finished

Hello from Commodore :)

Last time, I have installed a temporary alkaline battery pack into the calculator, to try whether it works or not. After that, I looked up the internet, to collect information about the AC adapter. I have found that, the original could provide 6V 400mA DC, through a normal, mono 3.5mm jack plug, where the pinhead of the plug is the positive polarity.

I ordered a configurable AC adapter, with 1A output, and option to set voltage from 3V to 12V. Also got a 2000 mAh NiMH battery pack, which is a low self-discharge version, instead of the original 500 mAh NiCd pack. Since the original pack was designed to 50 mA charge for 16 hours, there is no charge termination circuitry implemented inside. Which is fine for a NiCd battery. Fortunately, there is not much difference between the charge profiles of NiMH and NiCd, however a bigger capacity battery would miss the C/10h constant charge (fe.: 800mAh/10h=80mA), never charging up the batteries. However a low self-discharge version of the battery will be satisfied by the lower current.

Swapping the packs, and turning the calculator on, everything was fine. Plugging in the adapter I could measure 60 mA charge flowing into the pack, just as I expected.

It seams, that the device is expecting the battery inside heavily as a mediator/regulator, since not having the battery inside, just plugging in the adapter didn't do anything usable, just random characters on the screen (probably too low voltage for operating, didn't debugged any further).

Quickly made some new pictures, and TADA! Ready to use... erhh... charge. :)