Sony D-90 sled motor driver

m_saborio

Good day!

I just got my hands on a couple of Sony D-90 (D-9 for the folks in the US). They costed me 55€ and both were in very good cosmetic conditions, but both were not working. They turned on, the CD turned, but the laser did not move (the laser sled didn't move); hinting to the dreaded middle gear. So, I got my repair manual, soldering iron, and started repairing.

The problems inside both units were the usual suspects: middle gear of death was green and broken in several pieces, effectively blocking both the sled motor and the sled from moving. A few caps had leaked (both SMD and surface mounted) but only one of the units had damage to the traces. Replacing some of the caps required to find material to weld to, since the pads for a couple of caps were corroded away.

So, after replacing the gears, changing the caps and cleaning everything I reassembled and gave them a try. And they both did not worked. Or at least, they showed the exact same issue as the beginning: the laser sled was not moving.

I disassembled both units again and started troubleshooting. The sled motors work. I disordered the wires and drove them with a power supply. They started running at ~4,2V (a little bit too high I believe?). I then welded the wires again and turned on the Discman while measuring the voltage on the SD+ and SD- terminals. To my surprise, there was no voltage applied. The sled motors were receiving no power from the motor driver. The issue happened with both an external power supply and batteries.

I went back to the schematics and realized that the D-90 uses a Motorola MCP1715FU IC to drive the motors. I am guessing that the motor driver got damaged trying to move the blocked sled motor. I cannot see any apparent damage on the chip. I also checked the transistors feeding the IC, (Q437 and Q453) but they both look fine.

Therefore, I would like to askfor some advice. Is there a way to check if the MCP1715 is damaged? Are there any other components that I should check, that could prevent the sled motor from working? I've not being able to find a replacement chip here in Germany. Hence, if the advice is to replace the driver IC, do you have any idea where I can source the replacements?

Thanks in advance for the help.

kaosun

There's very low possibility the 1715 got damaged. Follow the schematic to check the power supply of 1715 which is pin 4 and 30 should be +4V; also, the servo cxa1272 pin 37 should receive +3.5V to output SD signal.