Hello from France,
I had a similar problem with my DP-47F : after a while ( between 10 and 30 minutes, depending on the room temperature ) when reaching the end of record position ( or when pushing on STOP ), the arm returned to the rest position but didn't lift down and the motor didn't stop running.
I hope you have the same problem because I found the origin of that problem : it seems that on some DP-47F there is an inversion between photo resistors CD2 and CD3 ( they are located on the little print board under the arm ). That makes that when being on the rest position, if you measure voltage on IC2 pin 4 you will find about -2.50 Volts. As the microprocessor needs -2.64 Volts for detecting the rest position, that works when components are new but fails after several years.
Inverting CD2 and CD3 photo resistors solves the problem. Be very careful when unsoldering / soldering those components. You can check that the CD1 and CD2 values should be the same on the part list of the service manual ( ku-5580 servo control unit ). I had to install a removable connector on the main board for checking the values of CD1, 2 & 3. After making the mod, the resistors values should be about for CD1 & 2, dark 1.5 MOhms and 1kOhms when lighten, for CD3, 6MOhms when dark and 2.5 kOhms when lighten. You should get about -2.80 Volts on IC2 pin4 after the mod and everything works fine :-) .
Let me know if you need some additional help : pascalvoisin38 @ free.fr
Sorry for my English :-( .
Pascal from France
I had a similar problem with my DP-47F : after a while ( between 10 and 30 minutes, depending on the room temperature ) when reaching the end of record position ( or when pushing on STOP ), the arm returned to the rest position but didn't lift down and the motor didn't stop running.
I hope you have the same problem because I found the origin of that problem : it seems that on some DP-47F there is an inversion between photo resistors CD2 and CD3 ( they are located on the little print board under the arm ). That makes that when being on the rest position, if you measure voltage on IC2 pin 4 you will find about -2.50 Volts. As the microprocessor needs -2.64 Volts for detecting the rest position, that works when components are new but fails after several years.
Inverting CD2 and CD3 photo resistors solves the problem. Be very careful when unsoldering / soldering those components. You can check that the CD1 and CD2 values should be the same on the part list of the service manual ( ku-5580 servo control unit ). I had to install a removable connector on the main board for checking the values of CD1, 2 & 3. After making the mod, the resistors values should be about for CD1 & 2, dark 1.5 MOhms and 1kOhms when lighten, for CD3, 6MOhms when dark and 2.5 kOhms when lighten. You should get about -2.80 Volts on IC2 pin4 after the mod and everything works fine :-) .
Let me know if you need some additional help : pascalvoisin38 @ free.fr
Sorry for my English :-( .
Pascal from France