Boot Up Diagnostics (Mega CD)
To help diagnose what is wrong there are a few common issues that can help pin-point an issue.
Make sure to use a known working Mega Drive for these tests.
Monitor the green and red LEDs on the Mega CD and compare them below.
- Green light (and sometimes red) on for split second, then off
- Green light and red lights back on and full boot
- Disc spins and then shows Press Start to run
- Green light on for a split second, then off
- Green light back on and hangs at boot screen with no MEGA CD / SEGA CD logo (Stuck at First Stage Boot)
- Black Screen
- Stuck at boot screen with no MEGA CD / SEGA CD logo (Stuck at First Stage Boot)
- Black screen with no LEDs at all on Mega CD
- Stuck at boot screen with no MEGA CD / SEGA CD logo (Stuck at First Stage Boot)
- Power board. Usually C25, C26 or C27 (100uF)
If you get the BIOS screen loading up, but basicallyt frozen with only the background (First Stage Boot), and you are not entering Second Stage Boot (animated logo) this is due to many things including the bus translator, the CD drive not connected, the ribbon to the CD drive bad, the program RAM or trace damage, a bad BIOS or 68k processor.
Dirt, flux and electrolyte that has leaked from capacitors can all cause no boot and issues. Warm up the board with a hot air station and clean with IPA and bamboo cloth while it is hot to remove all dirt and flux. Bath in warm vinegar to remove electrolyte then rinse in IPA.
I have seen several times simply the flux or electrolyte causing no boots.
Checkout the Second Stage Boot section for more information.
As well as the obvious of a bad laser which you can tune, there are other causese when the game spins, but constantyl spins never loading the game or failing. They include:
- Bad interconnect ribbon between CD and motherboard
- Bad Word RAM
- Bad traces between 68k and Word RAM
A great test is to use a flash cart and the 240p test suite.
Insert the flash cart into the Mega Drive while it is connected to the Mega CD and run the 240p test suite.
Make sure both the Mega Drive and Mega CD have power, and you have tested with the debug LED or multimeter the Mega CD does receive 5V when the Mega Drive turns on.
Then load up the test suite, and go into Sega CD Tests.
In here you will find a bunch of tests for confirming if the Mega CD is working.
You can test if the Mega CD BIOS is loading good. Run the BIOS CRC and info test. If the BIOS is good it will show a valid BIOS name and information.
The Program RAM needs to be valid and fully working to get past the blank BIOS screen. If the program RAM is bad, or the CD drive or ribbon, the BIOS will open up the background BIOS screen but won't load the logo or play any music.
Confirm the Program RAM is good using the 240p test.
The Word RAM (also known as Video RAM) are the two long chips near the edge of the board are two TC511664BZ chips.
If these are bad, you will see distinctive video glitches on screen. They will not prevent the Mega CD from getting to First or Second Stage Boot, and it will fully boot even without them, except you might not see anything on screen but still hear audio.
The Word RAM test often fails for me on fully working Mega CD consoles. So I am not sure how reliable the tests really are.
Do not confuse the WORD RAM with the WORK RAM.
The Word RAM is the two Video RAM chips (TC511664BZ) used for game loading and video data.
The Work RAM (MB8464A) is for saving game save data.
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