I still am backing reversed phase. Disconnect the feedback wire from the speaker transformer secondary & see if it shuts up. If it does put the wire back & reverse the connections of the OPT primary & see how that goes?

Otherwise its an induction problem probably in the det audio, or from a missing valve shield. prod wires with a chopstick to see if you can change the frequency, if it is not a shield.

6U7 would be the worst offender for feedback if unshielded.

Lead dress is important & wires away from the chassis can induct & cause feedback

Marc

Thank you very much GTC and Marc for your suggestions. It is much appreciated!!

Well, you guys certainly know your valve radios!

After reading Marc's post I thought I would start with the easiest test first. I found on my work bench under a pile of radio parts a matching metal valve shield. When I checked the radio chassis I found that there was no shield on the 6U7 valve! all the other valves had shields on them. To be honest I didn't think it would make much of a difference so I never gave the missing shield a second thought... but I installed in on the 6U7 valve anyway as it was originally before I neglected to replace it when swapping valves out.

WOW! now the radio is working beautifully!!! tunes in clearly on MW and SW. I can't believe the difference one metal shield has made and i'm really kicking myself for not giving it a second thought... ah well the joys of learning!

Thanks again everyone, now I can get to work on the cabinet. I really love the old Philips radios but i'm not particularly fond of the metal dial drive cords/cables that seem to do laps around the radio chassis....

I can't believe the difference one metal shield has made

Now you know why they went to trouble of putting them there.

i'm not particularly fond of the metal dial drive cords/cables that seem to do laps around the radio chassis

Dial restringing is definitely not my favourite task. Some radios have diabolical string schemes and I've heard Philips mentioned in that list.