Tread types and routing in Philips B5X14A vintage planar radio

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Many Philips radio's are using two different segments of wire on the drum of the variable capacitor to tune to the various stations.
The steel wire type forms one half and the "cotton" tread closes the loop, AM and FM circuit are using the same type of different wires.
The steel part is on vintage radio's subject to corrosion and breaks easily, I found it no problem to replace the steel by a "cotton" type.
Question: what is the reason Philips engineers have chosen for this two type of wire concept?

Re: Tread types and routing in Philips B5X14A vintage planar radio
On 09/05/2016 12:52 AM, Brasto wrote:
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Most likely to avoid stretch - so the frequency indicator stays true.

There was (is?) a fine braided highly flexible and strong wire that was  
used in those days for the same reason. I have an old roll of it in my  
shop that is used on jukeboxes for moving various things in the mechanism...

John :-##)
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(Please post followups or tech inquiries to the USENET newsgroup)
John's  Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
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Re: Tread types and routing in Philips B5X14A vintage planar radio
On Monday, September 5, 2016 at 3:52:08 AM UTC-4, Brasto wrote:
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 of the variable capacitor to tune to the various stations.
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, AM and FM circuit are using the same type of different wires.
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ly, I found it no problem to replace the steel by a "cotton" type.
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ype of wire concept?

There is a lot of history for tuner-cords, AKA Dial Cord, and as many types
 as there were radios. The wire-based dial cord - as already noted - was us
ed to prevent stretching, until (at least in the US) spring-loaded systems  
were developed to absorb the stretch equally. For the most part, modern rep
lacement materials are corrosion resistant and will easily outlast the radi
o.  

Other options include wire-core "Rigging Twine" used by scale modelers: Thi
s is a cloth-over-wire material that is useful for low-use systems as it lo
oks "original" and takes knots very well. There is also a braided material  
used by scale-sailboat racers that is extremely strong, flexible, corrosion
-resistant and able to take repeated stress. Probably your best bet if you  
intend to use this radio a good deal. Not cheap, but you don't need much ei
ther.

Plain ordinary braided Dacron fishing line is also useful as it gets over i
ts 'stretch' in the first use, and will remain stable after that. It is ver
y strong and comes in many weights and colors. And is very cheap. I would  
use this in lieu of the wire after pre-stretching it first.  

Good luck with it.

Peter Wieck
Melrose Park, PA

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