Troubleshoot Phillips 483x at converter stage (ech4 tube) (Techniek Radio/TV)

door ruudtx , 22.06.2018, 20:00 (2351 dagen geleden) @ Radiosterk

It is normal to have the oscillator signal (from triode) on the anode of the heptode.
There should be 3 signals - the rf signal when receiving a station, the osc signal and the difference signal, this is the IF signal 452 kHz. (Also the added signal rf + osc signal is somewhere theoratically, but is highly suppressed.)

As I understand the problem is that an unmodulated IF signal appears at the anode of the heptode. So the question is, where does this come from.

1) The heptode is occillating at 452
20 The front stage, the rf amp, is oscillating at tuned frequency. This can easy be eliminated by removing the tube.

So is there still a silent 452 kHz signal without the 1st rf amp?
If so, the heptode circuit is faulty, if not, it is the first stage causing the problem.