3DO:Sanyo Disc Drive Repair

Sanyo Disc Drive

3DO Model IMP-21J and the Goldstar models have the same drive.

The Sanyo disc drive is known to also have multiple critical failure points.
Most notably the critical failure points are:

-Ribbon Cable
-Composite gear destroyed
-Microswitches

One of the three above will likely fail before a laser would fail.

"I can't enter attract mode. All the 3DO does is show the 3DO logo, go to a black screen and keeps looping"

The most notable problems associated with this are the micro switches on the drive assembly and the ribbon cable.

The ribbon cable that connects from the disc drive LSI card to the actual optical assembly card (both cards that make up the 'disc drive') is a known failure point.
The ribbon cable will bend and often over time connections that are quite critical are broken.
Then the 3DO doesn't know what to do.

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  Poor Condition FFC

A replacement ribbon cable should be longer than the stock cable. The ribbon cable is a 30-pin 1mm pitch cable.
Similar to Saturn ribbon cable but it's just much longer and has more pins.

Here is a link for a recommended replacement proven to work on a Sanyo disc drive. It's 200mm long and is longer than the stock ribbon cable.
The metal contacts of the FFC should be on the same side.

https://www.mouser.com/ProductDetail/710-686630200001

"My 3DO keeps making some odd noise in the disc drive. It won't spin CDs at all"

The kiss of death.
On the optical assembly in the disc drive, there is a composite gear that sits between the worm gear and the motor.
It is likely damaged and destroyed.
You will require a replacement gear or ODE to fully fix your 3DO.

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  Culprit in the Center.

"My 3DO lens keeps hitting the CD spindle / My 3DO disc drive tray doesn't stay open long / My 3DO doesn't think there is a CD inside"

Your woes are signs of microswitch problems. There is a microswitch near the laser assembly that the laser hits and then moves slightly away from.
This is how 3DO knows the laser hits the center. Then the laser looks for a table of contents on the CD. It is possible this microswitch is faulty.

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  Microswitch connected by two white wires

There are also two other gears responsible for "open" detect and "close" detect.
They could also be faulty if the 3DO keeps moving the traverse gear when the disc drive retracts into the console OR if the console doesn't keep the disc drive tray open for a long period of time.
With extreme patience you could disassemble, clean, and rebuild the microswitch. This is not recommended and modern replacements should be sourced.

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  Open and Close Detect Microswitches