Wurlitzer 530 amplifier

Hallo ! Have repaired the amp but is concerned about the oscillator
Will it run at some frequecy even if the cobra and its cable aren't connected. Today the amp squielled very high which it has not done before.
Shall the cable be connected to get close to those 2 5 megahertz ?
If I insert a dummycoil into the input rca jack the squelling stops.
I have an oscilloscope so it must be possible to find out if the oscillator runs.
I have tried but could not verify if oscillating.
Thanks for some answer.......the jukebox and its cobra with cable is by the owner...not here in my workshop....

Hello Stewen,
I built a little circuit to test the oscillator/demodulator. [forum.jukebox-world.de]
In the meantime, I used this circuit with several Cobra Amps 506,524,528,530,532. As far as I remember, none of them had any "wild" oscillations with open input.
The PCB in the 530 has poor quality, beside all components around the osc.tube, you should check tracks, solder joints and chassis connections. You may also try another tube.
Rgds Jürgen