Mac 500 Circuit Diagrams Required

[techie1980]

Hi All

 

I have a number of MAC 500's that are in need of a bit of TLC.

 

All of them have PCB faults mainly surrounding Pan & Tilt errors or juddery movement.

 

The faults are definitely at board level as tried in different heads and replaced drivers and they are all fine.

 

If any one can assist it would be greatly appreciated

 

Thanks

 

Simon

[gyro_gearloose]

Pan and tilt juddery-ness is usually caused by the resistors used by the driver chip getting cooked. Their resistance increases, and because of this the driver chips limit the current to the motors too much. This then leads to a lack of torque from the motors, so there is not enough torque to move the head: hence the juddering.

 

I doubt you'll find a full PCB schematic, but I doubt you'll need one. Just have a look for the data sheets for the driver chips. Beware that the pan and tilt chips are different to the other driver chips. In the data sheets you'll find an example of a circuit which you can use to figure out which components do what on your Mac motherboards. You'll find that in some places Martin paralleled three resistors instead of using just one. This was done because three resistors can handle more current than one. If you remove the pan and tilt driver chips you can meter out the resistors associated with the driver chip. I am certain that you'll find one ore more that is faulty.