Does it play a disc OK... it's just that back in post 10 you mentioned it working I think.
Anyway, when you press to open the drawer, the line that goes to pin 6 of IC7403 that's labelled TRAYM should change it's logic level away from 2.5 volts. I'm guessing it goes to +5 to drive the tray one way and 0 to drive it the other. See what happens there. If it does change state, then check the outputs of the IC, pins 9 and 12 should respond by one going to +5 and the other going to 0 so driving the motor. To reverse the motor the two outputs change state, and when not driving the motor there is 2.5 volts on each. Do you get 5 volts on the motor ? Does the power to the motor switch off before it's opened or is there still 5 volts across it with the tray "stuck"
Also as an additional test if you turn the sled away from the disc center and then power the player up does the sled return back to the normal rest position at the center of the disc.
Anyway, when you press to open the drawer, the line that goes to pin 6 of IC7403 that's labelled TRAYM should change it's logic level away from 2.5 volts. I'm guessing it goes to +5 to drive the tray one way and 0 to drive it the other. See what happens there. If it does change state, then check the outputs of the IC, pins 9 and 12 should respond by one going to +5 and the other going to 0 so driving the motor. To reverse the motor the two outputs change state, and when not driving the motor there is 2.5 volts on each. Do you get 5 volts on the motor ? Does the power to the motor switch off before it's opened or is there still 5 volts across it with the tray "stuck"
Also as an additional test if you turn the sled away from the disc center and then power the player up does the sled return back to the normal rest position at the center of the disc.
Hi Mooly, Pin 6,9,and 12, all stay at about 2.5v regardless of me opening and closing the tray. On the 1401 terminal block for the tray I get about 4v on pin 4 marked TRAYM- all the time. On pin 3 marked TRAYM+ I get about 4v after pressing the tray open button and it goes away after closing the tray.
It's a bit odd as you seem to have two sort of unrelated faults.
Lets go straight to the motor for the tray. Have to be sure exactly whats happening. Connect your meter across the motor pins (Tray+ and Tray-).
1. There should normally be zero volts across here.
2. When you press to open the tray the motor should have voltage across it. What do you measure ?
3. Is the tray stopping while this voltage is still present... in other words stalling.
4. Does the voltage appearing across the motor correspond with the time that the "TRAY M" data line is at a different state form the normal "resting" level.
5. Does the supply (+5s pin 5 of the IC) hold up as the motor is powered and not collapse.
Also check the operation of the microswitches, one on the tray and one on the sled. Does the tray one operate correctly if you manually wind the tray out... can you measure it on ohms as closing correctly.
Same for the sled. On the CDM12 the sled winds back until it closes the switch, then the sled motor "kicks" the oposite way to move the pickup back out a fraction, so from memory the micro switch for the sled is normally open at rest.
Lets go straight to the motor for the tray. Have to be sure exactly whats happening. Connect your meter across the motor pins (Tray+ and Tray-).
1. There should normally be zero volts across here.
2. When you press to open the tray the motor should have voltage across it. What do you measure ?
3. Is the tray stopping while this voltage is still present... in other words stalling.
4. Does the voltage appearing across the motor correspond with the time that the "TRAY M" data line is at a different state form the normal "resting" level.
5. Does the supply (+5s pin 5 of the IC) hold up as the motor is powered and not collapse.
Also check the operation of the microswitches, one on the tray and one on the sled. Does the tray one operate correctly if you manually wind the tray out... can you measure it on ohms as closing correctly.
Same for the sled. On the CDM12 the sled winds back until it closes the switch, then the sled motor "kicks" the oposite way to move the pickup back out a fraction, so from memory the micro switch for the sled is normally open at rest.
Some good news. I put my meter accross tray+ and tray- and got no reading, but after pushing and proding I got a reading and when I tried the tray it opened and closed properly. I suspect a dry joint under the socket. I shall take the board out and rectify and return my results. The sled still did not work though.
Work on the tray problem first, make sure that's OK.
With the sled, again measure across the motor, pins 5 and 6 of connector 1400 (top left of circuit).
In normal playback the voltage across the sled "builds" slowly as the tracking error voltage increases, and when it reaches say 0.5 volts that overcomes friction and the sled "jerks" fowards slightly. That's all the voltage that's needed in playback to operate the motor.
And check the "limit" microswitch on the sled.
Most faults like this often are physical or mechanical in nature rather than electronic.
With the sled, again measure across the motor, pins 5 and 6 of connector 1400 (top left of circuit).
In normal playback the voltage across the sled "builds" slowly as the tracking error voltage increases, and when it reaches say 0.5 volts that overcomes friction and the sled "jerks" fowards slightly. That's all the voltage that's needed in playback to operate the motor.
And check the "limit" microswitch on the sled.
Most faults like this often are physical or mechanical in nature rather than electronic.
It's difficult to know whats happening. Close tray with disc in and disc turns. When it stops I get about 4-5v for a couple of seconds and then it dissapears. If I press play the disc will not turn. I have checked the socket and the leads to the motor and all looks ok. The motor itself reads about 15.5 ohms accross it's terminals.
5 volts pin 5 is correct.
Pin 10 and 14 are "earth" or zero.
Pin 7 looks like it should have permanent 2.5 volts derived from R3444 and 3445 down at the bottom of that page (pin7 IC7403).
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Connect meter across the sled motor (pins 9 and 12 of the IC 7401), open drawer, put disc in and play.
What does the voltage do ?
If no voltage appears measure volts from ground to pin 28 of the SAA7372 (line marked SL... or measure on R3414 the 12K resistor) and repeat above. Does the voltage change on the SL line ?
What does the voltage do ?
If no voltage appears measure volts from ground to pin 28 of the SAA7372 (line marked SL... or measure on R3414 the 12K resistor) and repeat above. Does the voltage change on the SL line ?
2.5 volts between 9 and 12 means the motor should be trying to turn as that's applied directly across the sled motor. Double check that reading.
If you are 100% sure on the reading then it points to a duff motor, those those on the CDM12 mechs will turn with very little volts.
Another check you can do. Turn off the power and disconnect the plug to the sled motor and apply a 1.5volt battery across the motor connection, you'll have to try it both ways round and the sled should fly to the end with 1.5volts.
If you are 100% sure on the reading then it points to a duff motor, those those on the CDM12 mechs will turn with very little volts.
Another check you can do. Turn off the power and disconnect the plug to the sled motor and apply a 1.5volt battery across the motor connection, you'll have to try it both ways round and the sled should fly to the end with 1.5volts.
Sorry the above is wrong. Administrator would not let me change it. this is how it is.
Connected meter between 9 and 12. No reading. Load disc. Reading goes to 2.5v for about 4 secs. then back to 0V. disc spins to read toc. stops spinning. mete then reads 2.5v for about 4 secs again then reverts to 0v. Pressing play does nothing.
Connected meter between 9 and 12. No reading. Load disc. Reading goes to 2.5v for about 4 secs. then back to 0V. disc spins to read toc. stops spinning. mete then reads 2.5v for about 4 secs again then reverts to 0v. Pressing play does nothing.
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