SEGA Master System II

Troubleshooting IC8
delivers the main  reference voltage (also referred to as  ) for the whole board. So yeah, we better make sure it works flawlessly 😄

Replacement
Virtually any 7805 (TO-220) will do the trick

Troubleshooting power delivery
The idea here is to ensure every IC is powered correctly by checking every "voltage in" pins.

Procedure
Check for  (+5V DC) presence on:

Troubleshooting the RESET circuit
The RESET circuit is active low (active at 0V); Any continuous 0V level will trigger a reset loop and prevent the board from initializing. That's why we need to check for  (+5V DC) presence on every RESET pin.

Procedure
Check for  (+5V DC) presence on:

What is the device power input?

 * +9V DC ± 10%, 0.5A.
 * 5.5mm x 2.1mm barrel plug.
 * Center-pin_negative.png Center-pin negative polarity (tip: +9V DC, sleeve: -9V DC).

Where I can find on the board?
The ground plane is present all around the board as a large copper via (see picture).