[Heathkit] SB-102 drive belts

[Paul Kraemer]

Working on an SB-102 which has dial cords and springs to drive the 
preselector capacitors
Problem is one cord was so tight it would cause the capacitor to distort 
mechanically near the high end of the tuning range causing scratch sound in 
receive while tuning and jumpy power output on transmit tuning.
As the plates meshed more and the tension relaxed everything was fine.
Did some of the SB's come out with string drive?  This is a very high sn ove 
15k. I thought they used rubber belts (O rings). The manual I have shows the 
belts.
I'm thinking of converting this to belts because lengthening that cord and 
re-stringing it is proving to be a real challenge to my sore fingers.
Does anyone have a size recommendation for the O rings?
Thanks in advance
Paul K0UYA