This is the main User Port Rev. 3 Dongle (THT version).

Find CASSETTE PORT PCB here

Find KEYBOARD SLOT PCB here

It's is providing two LED for voltage intocations (+5V and 9VAC). Further, there are pin headers for measuring those voltages at the user port. The +5V pin header allows connecting a 4 digit "precision" panel meter. I have some trust issues with those panel meters, but they are a nice light show.

Nov. 2024: There is a new version of the case (the STLs are ending on "_noVM_SX.stl"). This version allows to measure the voltages at the pin headers with your multimeter and configure the SX64 or C64 option via jumper. That jumper should be the type with a "handle".

The solder bridge JP1 near the pin header J6 (which has to be placed) needs to be open!

Therefore, it has to be cut along the gap with a scalpel or exacto knife. It is best to check the success with an ohmmeter/multimeter.

The cable for measuring the voltage (+5VDC and 9VAC) at the pin pin headers consists of two AWG24 wires, preferable in different colors, on one end is a two way Dupont connector, on the other end 4mm lab connectors. Holding them together with cable ties is maybe not such a bad idea.

To prevent short circuit, you should plug the lab connectors in the multimeter first, there are some security multimeter connectors, too.

Analog Switch IC (User Port Dongle)

Originally, the analog switches are 4066. The 74HC4066 was also tested and works perfectly.