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

Leon Crampin · 13th Feb 2020, 2:02 pm

David, as far as I remember, the reel hub clutches have a metal disk below the solenoid coil, rather like a large washer with a textured (in the metal) surface. This disk has to be axially free for the clutch to operate correctly.

The reel hub solenoids have 2 functions, braking and fast wind engagement. For braking, where the tape has to be brought to a reasonably gentle halt, the solenoids are partially energised via a resistor; fairly large to dissipate some power. This gives a relatively soft halt without tape snatch.

For fast wind, the take up hub solenoid is fully energised - you will hear the "washer" jump up with an audible click and the hub will be locked solid if the circular rubber strip in the upper hub is in good condition.

It's always worth checking the 25V supply to the solenoids and relays. The AEG selenium rectifier positioned at the front of the lower chassis is notorious as a failure item, and is best replaced with a silicon bridge.

Leon.

13th Feb 2020, 2:02 pm	#136
Leon Crampin Octode Join Date: Nov 2005 Location: Surrey, UK. Posts: 1,874	Re: Grundig TK 819 Any Useful Info David, as far as I remember, the reel hub clutches have a metal disk below the solenoid coil, rather like a large washer with a textured (in the metal) surface. This disk has to be axially free for the clutch to operate correctly. The reel hub solenoids have 2 functions, braking and fast wind engagement. For braking, where the tape has to be brought to a reasonably gentle halt, the solenoids are partially energised via a resistor; fairly large to dissipate some power. This gives a relatively soft halt without tape snatch. For fast wind, the take up hub solenoid is fully energised - you will hear the "washer" jump up with an audible click and the hub will be locked solid if the circular rubber strip in the upper hub is in good condition. It's always worth checking the 25V supply to the solenoids and relays. The AEG selenium rectifier positioned at the front of the lower chassis is notorious as a failure item, and is best replaced with a silicon bridge. Leon.