Customer Repairs

Open-Reel Tape Recorder, Grundig TK141

Repair H166

 The machine's three rubber drive belts were broken from old-age but I was able to find a set of belts that are approximately the correct dimensions.
I removed the chassis and detached the motor lower bearing. I was then able to thread the two main reel drive belts through the aperture provided and pass them round the pulleys.
The third belt was fitted to the counter.
There were several minor electrical faults present.

 There are three fuses fitted at the rear power selection panel. The mains fuse was intact. The 1.6A fuse was intact but fitted in the place of a smaller 100mA fuse. The latter fuse was fitted in place of the 1.6A fuse and was open circuit.
Fitting correct fuses restored power to the amplifier.
I carried out checks on the audio power output stage and found the standing current was wrong at 90mA. I made adjustments and this is now correct at 50mA.
I also tested the power transistors, together with three driver transistors as these are employed in a DC bias system which relies on correct electrical performance to attain proper operation of the amplifier. All transistors tested OK.
The pressure roller had seized on its shaft. I removed the assembly and cleaned the shaft and the roller surface then lubricated the shaft and refitted everything. The roller now works smoothly.
I cleaned the audio and erase heads together with the metal tape-bearing surfaces.
In operation I noticed the main drive belt is so long that mechanical resonance from the motor can set up oscillation resulting in a reinforcement of background hum. I drilled the chassis and fitted a simple damper so that belt oscillation is curtailed.
I cleaned the reel surfaces and cleaned and slightly roughened the rubber idler wheel. The rubber is starting to craze but is still pliable and should be serviceable, at least for a couple of years.
I lubricated the plastic play/wind selector mechanism with grease to smooth its operation.
Sometimes there is a lot of crackling when first switched on. I traced this to the mains on/off switch which is lazy in operation. This should rectify itself with use. Occasionally the indicator lamp would flicker but this is slight tarnishing at the lamp contacts and nothing to worry about.
Play appears to be pretty good and the tracks appear to be aligned correctly for the sample tape provided.

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