UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Motorola 251 8 Track Motor Resistor Burn Out!

Magical · 19th Nov 2020, 6:31 pm

Hello,
I’m after a bit of help again. I’ve refurbished a Motorola 251 8 track, which runs great....mostly. The motor supply circuit has a 2.7 ohm resistor in series. When running the unit everything is fine and the motor pulls about 60mA then, for no apparent reason, the motor starts to pull 1.5 to 2 amps and fries the resistor. This can take up to an hour to happen. Everything is running free, no binding. I’ve measured resistance across the motor through 360 degrees of rotation and get between 5 and 10 ohms, so nothing seems awry there. There is a 1000mF cap from live to earth in the circuit too, but this appears to be ok. Replacing the resistor restores motor function until this happens again.
Anyone any ideas what I need to look for please?
Thanks again.

19th Nov 2020, 6:31 pm	#1
Magical Triode Join Date: Jun 2020 Location: Stoke-on-Trent, Staffordshire, UK. Posts: 33	Motorola 251 8 Track Motor Resistor Burn Out! Hello, I’m after a bit of help again. I’ve refurbished a Motorola 251 8 track, which runs great....mostly. The motor supply circuit has a 2.7 ohm resistor in series. When running the unit everything is fine and the motor pulls about 60mA then, for no apparent reason, the motor starts to pull 1.5 to 2 amps and fries the resistor. This can take up to an hour to happen. Everything is running free, no binding. I’ve measured resistance across the motor through 360 degrees of rotation and get between 5 and 10 ohms, so nothing seems awry there. There is a 1000mF cap from live to earth in the circuit too, but this appears to be ok. Replacing the resistor restores motor function until this happens again. Anyone any ideas what I need to look for please? Thanks again.