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Post subject: [MDP-450/650] Player repair info needed Posted: 30 Jul 2020, 01:30 |
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Joined: 30 Jul 2020, 00:47 Posts: 2 Location: United States Has thanked: 0 time Been thanked: 0 time
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I have had my player since about 1993 and after about 10 years it would not reliably load disks or open/close the tray. It would run the loading mechanism with ratcheting noises whenever it powered on without a disc in the tray. So, not having time to open it up I abandoned using it until recently. The original problem was easily fixed with a new belt, but things quickly went downhill after playing only part of one disc....it would skip to a completely different track and eventually stopped reading either CDs or LDs. So I ordered a "new" laser head and installed it, but before I could get the new head verified it refused to spin up while the head attempts to read the disc. I have verified the spindle motor is good and the laser is attempting to focus on the (stationary) disc. So here are my questions, referencing the repair manual System Control board. 1) The System control board has 4 signals out to the spindle motor circuits. SP OFF, 2FH, SP ERROR, SP UNLOCK. When I press PLAY the signals are 0V, continuous 5V pulse, -5V, and 0V. I assume the 2FH is to control spindle speed and the SP ERROR indicates direction and speed. So what are the correct states of SP OFF and SP UNLOCK? And are they active high (5V) or active low (0V)? 2) Does anyone know what inputs to the control chips determine whether the spindle motor should spin? 3) Any insight into the control chip logic would be greatly appreciated.....
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