Replacing link cable in 1950s Blaupunkt Car radio

[Old Sparky]

This is a radio in which I had already replaced all the waxed paper capacitors, the reservoir & smoothing capacitor, and a number of other faulty components. The original mechanical vibrator was missing, so I fitted a solid state one from the 'Antique Auto Co.' ( obtained from AC James of Paulton, Bristol ) All of this was done some time ago, and the radio tested. At the time it was working OK, but left in store. When I retrieved it a short while ago, I discovered that the internal insulatiion of the wires in the link cable were perished, so I conclude that the oscillations are due to my new, unscreened cable. This could be because I've routed a lead carrying HT+ down the same length of sleeving as the screened signal lead, perhaps due to capacitive/inductive coupling. THe LT +, -, & switched + leads are in a seperate piece of sleeving running alongside the signal & HT leads, with the two fastened together in several places with cable ties. Not a good idea, maybe, but all the leads are, of neccesity, in close proximity to each other at both the head unit end, and at the plug/psu end! Because all the two-unit valved car radios I've ever come across used a multi-core cable with an overall outer screen to connect the two parts together, I was probably wrong to use unscreened wires for the job. After all, those designers back in thee 1950s knew what they were about, and the setmakers surely wouldn't have used expensive screened cable unless it was necessary! The Radio is a Frankfurt 'R' series dating from about 1956.