Re: DC GD-ROM repair

Post #1 » Fri Jan 21, 2011 11:59 am

I've found with the GD-ROM's used in the Sega/Chihiro amusements games like Ghost Squad, HOD 3, etc and the DC itself is that the spindle motor fails. What happens, specifically, is that the commutator on the spindle motor wears to the point that the small spring brushes (no carbon tips) that contact the commutator then touch, causing a short. Provided it hasn't blown the motor driver IC, I've been able to disassemble the motor, refinish the commutator, and modify/repair the existing brushes and it works like a champ.

I was a 35mm camera and Sony 8mm video camcorder bench tech for seven years and worked with small DC micromotors all of the time so I've had a very good track record repairing sealed motors.

Just thought I'd pass this along.

Greg

Post #2 » Fri Jan 21, 2011 1:36 pm

One of my Dreamcast's has a broken gd-rom drive, but it isn't the motor thats bad, it is the laser.

Post #3 » Fri Jan 21, 2011 9:19 pm

Interesting info to have thanks.

Post #4 » Sat Jan 22, 2011 10:44 am

TeamXlink wrote:One of my Dreamcast's has a broken gd-rom drive, but it isn't the motor thats bad, it is the laser.

The optical pickup/laser can be replaced but you'd need another DC for the parts. If you have a broken spare, you can swap out the parts (I'm sure you already thought about this).

If anyone has a broken DC with a motor issue, I can probably repair it.
PM me.

Greg

Post #5 » Wed Feb 02, 2011 4:20 pm

One of my DCs has a broken GD rom
it does half a spin and then stops and it stops the system from starting.
I tried moving the GD rom to my other DC and it didn't work so I'm sure the problem is with the GD rom not something else.
What do you think I can do?

Post #6 » Fri Feb 04, 2011 8:28 pm

daniel116 wrote:One of my DCs has a broken GD rom
it does half a spin and then stops and it stops the system from starting.
I tried moving the GD rom to my other DC and it didn't work so I'm sure the problem is with the GD rom not something else.
What do you think I can do?

I'm going to guess that the spindle motor maybe bad (i.e., a dead spot on the commutator). Only way to confirm would be to take the unit apart so that you can get to the red and black wires going to the spindle motor. If you have a volt/ohm meter, with your test leads touch across where the red and black wires solder onto the back of the motor; you should read approximately 18 ohms. Turn the spindle by hand a few times and check your readings again. If the reading is anything below 17-18 ohms, there's a short - most likely the motor spring brushes starting touch touch due to excessive commutaor wear. Hope this helps.

Greg

Post #7 » Thu Feb 10, 2011 11:41 pm

I've also repaired a faulty DC spindle motor.

Turns out that somehow one of the brush fingers had managed to work itself to the wrong side of the communicator. This caused it to actually spin backwards at times (if it worked at all).

It was a relatively simple procedure to open the motor and fix the issue. The motor still works to this day. However, the Dreamcast it was in has become a parts machine for other reasons. I've since used the motor a few times in various hobby projects, but generally just have it around as a spare.

Post #8 » Fri Feb 11, 2011 12:21 am

daniel116 wrote:One of my DCs has a broken GD rom
it does half a spin and then stops and it stops the system from starting.
I tried moving the GD rom to my other DC and it didn't work so I'm sure the problem is with the GD rom not something else.
What do you think I can do?

When you say you moved the GD-Rom to your other DC, do you mean you moved the entire unit (with the underlying GD-Rom control board)? If it's the former, then you haven't yet eliminated the GD-Rom board from the equation.

Some DCs (model 2) actually don't have a separate GD-Rom controller board. Instead, the controller is integrated into the main board.

If you don't have a multimeter (shame on you!) and want to narrow it down further to either the motor or the board, you can try to swap just the top half of the motor/laser housing (the part that 'floats' on the rubber bushings) with one form a known working DC. To do so (if you have a 'normal' DC with the separate GD-Rom board) you need to remove all the screws from the aluminum looking piece on the underside of the GD-Rom unit (2 are hidden under a strip of adhesive fabric near the back). After that, the underside can be removed and the board inside will be free enough to safely unplug both motor leads, and the laser ribbon. Repeat with the working DC, and swap the parts. If you have a DC with the integrated main-board GD-rom controller, you will see exactly where all this stuff plugs in as soon as you remove the top of the DC... No more unscrewing required.

Hopefully, it's the motor, because that's going to be a heck of a lot easier to repair/replace than the GD-Rom controller.

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