A group of my friends are DJ’s known as Desi Jammers, and did DJing at my Birthday BBQ. One of their turntables had an issue with the LCD reading “no disc” The CD would never spin up and its like the laser had issues reading the disc.

First step was to remove the laser pickup assembly the CD loader. This is a front loading CD ROM drive.

At first I saw that the right metal connector was touching the nearby motor which probably grounded it out possibly causing the problem to begin with. Photo doesn’t show this, photo is showing after I already bent it where it should be. This switch is like a sensor that tells the system when the laser sled has reached the beginning of the path that it travels. I put it back together to see if that was the issue, that was not.

If the motor wasn’t spinning, I was thinking this chip could have been faulty since it is connected to the motor, so it drives the motor to begin with. No other component has any noticeable damage, but this one may have had internal damage not noticeable from the outside. Also I suspected it overheated since it has a not so great heatsink on top. My friend thought the motor was burned, but I ran voltage through it from a battery and the motor spins fine. Plus it passed the continuity test that I did earlier.

BA5979S schematic and pinouts.

Reverse side of the mainboard and power supply. Top right is where the BA5979S chip is soldered.

I used a clear CD that you find at the bottom of a spindle of CD-Rs to troubleshoot, so I can see whats going on.

Clear CD, and one desi CD to check for playability.

Looks like a photo diode, at first I thought it was the laser diode.

The laser diode shines, and the laser optics read the pits on the CD, the pulses of the pits are then detected by this Photo diode. Which sends the data back to the controller.

Photo diode.

Spring that pulls the top portion of the CD loader down when the CD is in and keeps it firmly in place.

Laser diode shining through the optics. This laser diode is from a CD Clock Radio that I found in the trash several weeks back.

Engineering plans to fix this bloody thing.

Notice the laser sled assembly on the left closely resembles the one on the right which is from the CD clock radio I found in the trash.

Both assemblies were really similar so I decided to try the laser pickup assembly from the CD clock radio I found in the trash into the DJ turntable. Only problem which I did was I didn’t put the paper all the way on the bottom which allowed the motor to touch the metal thing and spark and it messed up again. Stupid. However, I got the motor to spin which proves that the BA5979S chip was never the problem.

I tried it again after that thing touched the metal, but it didn’t seem to work. I thought maybe I messed up the laser diode, because it didn’t’ seem to be shining anymore. So I decided to get one from a CD burner I found in the computer which I also found in the trash.

CD burner from the trash.

CD burner from the trash, different laser pickup sled. The gearing is kind of cool too. If something is forced for whatever reason, like some debris gets stuck or whatever, it has some kind of spring loaded gearing thing kind of like a clutch which is wild, look closely. Its like a gear on top of a gear.

Laser diode enters from the bottom, goes through a series of lenses and mirrors.

The mirrors and prisms for the laser optics, its pretty awesome.

I Desoldered the laser diode.

The laser diode from the sled assembly in the DJ turntable looks way bigger, but I figured it may still work.

The board that connects to the laser has two metal discharge points on the board to the right. I read somewhere that you need to short circuit this and discharge every time you are trying to work with it. Maybe for electrostatic reasons, or that surface-mount capacitor that’s also located on that board which is connected in a parallel circuit probably needs to be discharged.

To pull the sled off its tracks, you have to pull the bar that it slides through off. To pull the bar off you have to bend the plastic thing over to the right and pull on the bar.

Laser diode removed, penny shown for scale. Shows how small the stuff I’m working with.

Look how closely the two laser pickup assemblies look alike. The right one is from the Turntable, the left one is from the CD Clock Radio I found in the trash. I wanted to try and make that one work again in the DJ Turntable.

I took the balls and springs off. These help to keep the CD snapped onto the spindle. However that’s from top loading CDs, and this DJ turntable is a front loading one.

CD wasn’t being gripped to the plastic. So I added a padding I got from the CD burner. I tried a rubber gasket I found at CSU East Bay on the ground of the parking lot one day, but those few extra millimeters of thickness caused the laser optics not to focus properly on the disc.

I tried switching the sleds since the CD didn’t work well with the spindle from the clock radio. However the sleds don’t swap easily. When you use the CD clock radio entire laser pickup assembly, it doesn’t fit into the DJ turntable because the motors are too big even though they have the same specifications.

The mess of trying to fix it. Chipotle in the back. Clock radio, compressed air from that right guard deodorant, solder, soldering gun, cd burner, dj turntable, laser shit, monkey wrench.

Split to pieces.

Drilled a hole through the top CD spindle in order to undo the screws underneath.

Drilled large holes to remove metal to try and pull the motor off. The top spindle thing doesn’t come off.

The drill accidentally ripped off the wires connecting to the motor. Superbad.

Looking at the bottom of this, I figure I can bend the 4 metal tabs (2, 4, 8, 10 o’clock positions), open up the motor and solder new wires on. However that was difficult. I discovered something even better. Additional metal connectors on the bottom which have been snapped off.

I managed to solder wires at those points. I used a continuity tester to determine the anode and the cathode and soldered it to the small printed circuit board (PCB). At first I was going to have one big motor and one small motor since the small motor with the small gear wouldn’t match all the gearing for this sled assembly. However, I realized that while the spindle is not removable on one motor, the gearing is removable on the other. So I managed to get both small motors on the assembly so that later when I put it all back together, it won’t have issues fitting in. The sensor at the right is the next thing to fit on to this assembly.

I drilled another pilot hole and then the screw to get the sensor on. I stripped the screw badly though. So then I used thick wires soldered to the PCB to make the sensor rigid. I used another solid wire soldered to another point to hold the motor wires away.

Completely re-engineered laser pickup assembly. New sensor position, old spindle. New metal frame, new shock absorbers, new gear, old motors, new ribbon cable.

Another View

Testing

CD playing, DJ turntable now works good. The only bad thing out of all this, is when I was pulling out the spindle motor from the old assembly, I accidentally bent the spindle a tiny tiny bit which makes CD reading bad in the later tracks after like track 8. When the CD spins, there is more gyroscopic stability in the center since its closer to the spindle, which means early tracks play fine, but later ones not well. The small amount of wobbling doesn’t allow the laser to focus well. However with this working now, it allows to the computer to hook up without any issues and even without that, a two turntable system makes the whole idea flawless.

• Digg
• Stumble it!
• Reddit

• Sony Cybershot W120 Teardown and LCD Replacement
• How to Hook up an N-Channel MOSFET
• LCD Screen No Power, No Signal