Internal modem upgrade. Some company sold them. The J grabbers are so that the user could install it without soldering. The board in the battery pack allows for using rechargeable nicd cells in the pack, and having the computer recharge the batteries. The nicd pack has a resistor on the board and one of the pins is connected differently, and this tells the computer to expect the lower voltage and to allow the wall power to charge the batteries. There were even other battery packs that had their own power jack. The point of that was 2 things, one, the pack could be charged by itself outside of the machine, but more importantly it allowed the battery to act as a UPS for the computer. The pc-8300 (similar machine) was often used as a part of other equipment that needed to run 24/7. The normal power jack and battery, even with the rechargeable pack installed, does NOT act as a UPS. If the wall power is plugged in, then power comes from that wire - period. If the wall power goes out, then the computer dies. The battery pack is not in the circuit ready to take over, even though it is being charged. But the special pack with its' own power jack does. To use that, you plug the power into that pack instead of the normal jack, so that the switch in the normal power jack stays closed and only the battery powers the computer. Then the special pack does have a couple diodes in it so that when the wall power goes out, the batteries are already connected and start powering the machine.
Internal modem upgrade. Some company sold them. The J grabbers are so that the user could install it without soldering.
The board in the battery pack allows for using rechargeable nicd cells in the pack, and having the computer recharge the batteries. The nicd pack has a resistor on the board and one of the pins is connected differently, and this tells the computer to expect the lower voltage and to allow the wall power to charge the batteries.
There were even other battery packs that had their own power jack. The point of that was 2 things, one, the pack could be charged by itself outside of the machine, but more importantly it allowed the battery to act as a UPS for the computer. The pc-8300 (similar machine) was often used as a part of other equipment that needed to run 24/7. The normal power jack and battery, even with the rechargeable pack installed, does NOT act as a UPS. If the wall power is plugged in, then power comes from that wire - period. If the wall power goes out, then the computer dies. The battery pack is not in the circuit ready to take over, even though it is being charged. But the special pack with its' own power jack does. To use that, you plug the power into that pack instead of the normal jack, so that the switch in the normal power jack stays closed and only the battery powers the computer. Then the special pack does have a couple diodes in it so that when the wall power goes out, the batteries are already connected and start powering the machine.
That's pretty cool.
The add on board is a 300 baud modem.
Thanks. I googled the 74xxx chip and it came up as a buffer but I must have typed the number wrong. Mystery solved! And now I can delete it.
Interesting for sure.
You may like Joe's Classic Arcade. He repairs arcade games, pinball, and old radios.
@drivewayshop I just started watching My Mate Vince. I don't need another hobby lol