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Hints, Tips and Solutions (Do NOT post requests for help here) If you have any useful general hints and tips for vintage technology repair and restoration, please share them here. PLEASE DO NOT POST REQUESTS FOR HELP HERE!

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Old 9th Sep 2020, 6:27 pm   #1
Leon Crampin
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Default Improving a stiff tuning drive - FB 10

In cheap sets such as the above, the tuning cord runs around fixed pegs rather than pulleys. In the FB 10, this gives rise to drive friction and hysteresis, making fine tuning difficult. On this set, the whole tuning carriage rocks as the set is tuned, due to friction around the pegs.

A fix is to wrap the pegs with PTFE tape. On the FB 10 it's the pegs at either end of the carriage which give rise to the most friction due to a large wrap angle. The tape need not be applied neatly - the cord will make its own groove in the tape which stops it unravelling.

The improvement in the drive feel and tuning accuracy is considerable, and the pointer now moves for small adjustments as it should.

Leon.
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Old 20th Oct 2020, 6:47 am   #2
wireless_john
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Default Re: Improving a stiff tuning drive - FB 10

Something I hadn't noticed! You've prompted me to have a more critical look at mine now. This is the Kolster Brandes FB10 you're talking about I take it?

John
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Old 20th Oct 2020, 8:37 am   #3
vinrads
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Default Re: Improving a stiff tuning drive - FB 10

I had noticed that problem ,I did once thought about modifying it to pulleys ,but never did it , it 's a very poor design ,destined to give trouble. Mick.
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Old 20th Oct 2020, 2:12 pm   #4
Leon Crampin
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Default Re: Improving a stiff tuning drive - FB 10

It is indeed the Kolster-Brandes set - I should have made that clear.

Although results may vary with the type of drive cord used, I can confirm that now the set is fully restored, the drive has remained smooth after quite a bit of use. Lower friction should also enhance the life of the drive.

Although originally a very cheap set, I admire the production engineering (eg. how many uses for a rubber grommet - feet, dial lamp holder retainer, speaker mounting etc.). I also like the use of a heater transformer as opposed to a dropper, with 6.3V valves to keep heater cathode voltages low.

Leon.
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