Truvox R. 42 Reel to Reel Check Out

[DMcMahon]

I think best first to power up the motor to make sure the motor works before I get too involved in pulley repairing.

David

[DMcMahon]

Fitted a new 3 pin mains plug fitted with 1 amp fuse.

Checked the 30mm glass 250mA internal mains fuse, it was correct value but when disturbed it fell apart so fitted a new fuse.

Disabled the DC power side so as to power up just the AC side to test the motor. Discovered that not the same as shown on the schematic. The schematic shows 2 DC power rails fed from 2 separate ridge rectifiers with 3 smoothing/filter capacitors.

But this unit only has one bridge rectifier and 2 capacitors, not sure if this is a different build version or whether the parts are missing. Later will check the circuitry that should be powered from the second bridge rectifier to determine how it receives power.

My R.44 does have 2 bridge rectifiers and the 3 capacitors as per the schematic.

Powered up OK, 19V at mains transformer secondary to the bridge rectifier. 5 volts at the second secondary winding which feeds the bulb (which lights up) above the VU meter.

No sign of the motor moving when the 3 tape transport piano keys actuated, hopefully just a bad contact at the motor deck switch, rather than a dead motor.

David

[DMcMahon]

Checked the deck switch which switches the mains live through to one side of the motor winding, it visually appeared to be mechanically/physically making when actuated but not electrically on voltage/resistance measurements.

Removed the switch contacts and cleaned up fairly heavy tarnishing and straightened one contact for better physical contact.

Note the cut off white wire on one of the contact arms. The schematic shows 2 white wires (which are the switched output side of the switch). The schematic shows the second white wire going to the mains voltage switch and when switched to 120V would switch the mains live to the 120 volt motor winding. This particular machine does not have the mains voltage selection switch so explains the cut off wire.

Motor now is running very well, smooth and quiet and starts rotating at about 80 volts.

Still unable to remove the pulley off the motor shaft, tried holding the motor shaft with pliers and using mini mole grips tried to turn the pulley but rock solid. Due to limited access space difficult to do this so have partially removed the motor (still connected by the wiring) for better access. Quite a few bits had to be removed to access the motor mounting screws.

Have tried some gentle heat but still no sign of the pulley loosening up on the motor shaft, maybe more heat required.

[DMcMahon]

With more heat managed to remove the pulley, definitely a 1 piece part.

Not much rubber left but what there is, is not keen to clean off.

David

[Borderer]

At least the pulley came off undamaged. Is is aluminium or zinc alloy?

[DMcMahon]

Pretty sure it is Aluminium.

Cleaned up the pulley, nominal dimensions of pulley where the rubber sleeve resides is 12mm high by 19.1mm diameter (i.e. the diameter of the hole in the rubber sleeve), with the outside diameter of the rubber sleeve around 26.6mm to line up with the diameter of the large speed step diameter.

As a temporary measure fitted a pinch roller rubber tyre to the motor pulley. It may be non starter because it is larger diameter than 26.6mm plus the rubber is quite soft and somewhat cracked. Am hoping that it may basically function and get fast winding working for a while to be able to progress other aspects of the recorder, until can work out a better more permanent solution.

Need to re-assemble various bits before can see if it may work.

David

[ben]

You're making good progress there, David. I'm reading with interest!