Drive Cord Rewinding Idiots Guide

[DMcMahon]

I hardly ever do it nowadays but when I do rewind a tuning scale drive cord (either original cord or new cord) I always struggle even when trying to follow the drawing in the appropriate service manual.

Is there an idiots guide/BKM/Do's & Don'ts/Tips for this task ?

David

[cathoderay57]

Difficult to answer because, as you're no doubt aware, they are all different, some more tricky than others e.g. Philips. Some rather obvious tips are:
1. Use non-stretchable cord. Examples are pike fishing line, or stranded nylon (although this tends to slip unless taut, is difficult to terminate since the end frays easily and knots tend to come undone). Original waxed cotton cord is hard to find. For wire drives I found Beadalon (used for jewellery stringing) works well and comes in a range of diameters.
2. Get the cord to the right length, terminate on the spring and stretch the spring to fit over the lug on the tuning capacitor drum to add tension. Masking tape is useful to temporarily hold the cord in place while stringing up.
3. Make sure you add sufficient turns around the tuning spindle if it is a friction drive. Sometimes a light application of talcum powder on the spindle helps absorb any residual surface grease and aids grip.
4. Clean old grease off the pulleys and tuning capacitor bearings and lubricate lightly with 3-in-one oil or similar. Free running moving parts mean the cord has to work less hard. Pay attention to any sliding pointer assembly and make sure it is clean and lightly lubricated. Silicone grease works well.

Jerry

[vidjoman]

There’s no problem with frayed ends on nylon thread, just touch the cut end on a hot soldering iron. Knots can be secured with a dab of nail varnish, in any colour you have to hand.

[PsychMan]

One point I'll add, if you're having a mare with a particular rewind, and in the process your new cord suffers any damaged strands, Don't assume it will be ok, - it will only get worse and break at that point.

This happened to me with a HMV 501, not the funnest chassis to remove. I cant remember why but I found this one hard and ended up damaging the new cord on some of the metal work. The damage was very light so I didnt worry too much and fitted the chassis back to the case. 1 month later it went and Im still working up the courage to resume work on that machine

Adam

[radiomobile]

If you don't have the instructions don't forget to ensure that you restring the system with the pointer going the right way! usually left to right with increasing wavelength (reducing frequency). Most of us have at some time ended up with the pointer travelling in the wrong direction...very frustrating. A useful tip is to start with the gang fully closed and the pointer at the 550m end of the scale. This also protects the tuning condenser vanes against accidental damage.

[DMcMahon]

Originally Posted by cathoderay57

2. Get the cord to the right length, terminate on the spring and stretch the spring to fit over the lug on the tuning capacitor drum to add tension.
Jerry

If the original cord is broken/missing how does one know the correct length ?

Many thanks to all who have responded, it is all very useful.

David

[Alistair D]

As far as knots are concerned. This thread gives a lot of options.

https://www.vintage-radio.net/forum/...d.php?t=142721

The only other thing that comes to mind was that I used get frustrated if I let go of the loose end of the cord and it fell of the pulleys. My solution to that one was to use a small weighted croc clip that could be attached to the cord at various places along it's length to maintain the tension.

Al

[cathoderay57]

Originally Posted by DMcMahon

If the original cord is broken/missing how does one know the correct length?

Very occasionally the service sheet will state the length. Mullard/Philips sometimes do, most usually not. Just string the drive loosely using masking tape; then pull tight and cut the cord leaving sufficient to attach to one end of the spring such that by extending the spring to about 50% extension will enable the other end to slip over the lug on the tuning drum. Jerry

I would hazard a guess that most cord runs are undocumented, the first done by the designer of the radio, the production run by "ladies on the line" who could simultaneously knit a jumper, make tea and change baby. We haven't a hope!