UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Sony SL-C20

Studio263 · 30th Aug 2018, 9:55 am

Don't start taking the motor apart until you are sure the sensor is faulty. If the PG sensor isn't working (the one in your picture) the motor will still spin up but then stop after a short while, so its probably not that which is wrong. If the hall sensors which commutate the windings are faulty then the motor will limp round for a bit if you spin it up by hand when it is supposed to be working, or at least some resistance will be felt from the coils which are energised. Do your test in 'still' mode, this excludes things like the capstan motor FG sensor and the reel sensors.

The diagram will show which motor pins have the hall sensor outputs on them. Energise the sensor from a bench supply (motor disconnected of course) and scope the outputs as the shaft is turned. Only then, if something it proved to be incorrect, is it worth dismantling the motor. This is not a risk-free operation, it is possible to damage things like the head tips when the nut on the bottom of the shaft is released.

Don't rely on the internet to do your diagnosis for you, it is usually wrong. Make your own tests instead, its the best way.

30th Aug 2018, 9:55 am	#5
Studio263 Octode Join Date: Apr 2007 Location: Hampshire, UK. Posts: 1,578	Re: Sony SL-C20 - Issue with Play FF RW Don't start taking the motor apart until you are sure the sensor is faulty. If the PG sensor isn't working (the one in your picture) the motor will still spin up but then stop after a short while, so its probably not that which is wrong. If the hall sensors which commutate the windings are faulty then the motor will limp round for a bit if you spin it up by hand when it is supposed to be working, or at least some resistance will be felt from the coils which are energised. Do your test in 'still' mode, this excludes things like the capstan motor FG sensor and the reel sensors. The diagram will show which motor pins have the hall sensor outputs on them. Energise the sensor from a bench supply (motor disconnected of course) and scope the outputs as the shaft is turned. Only then, if something it proved to be incorrect, is it worth dismantling the motor. This is not a risk-free operation, it is possible to damage things like the head tips when the nut on the bottom of the shaft is released. Don't rely on the internet to do your diagnosis for you, it is usually wrong. Make your own tests instead, its the best way.