Setchell Carlson...588 dial, 407 cab, 420 chassis(?) Serious need of a schematic.

[bob91343]

No difference in hum while touching 6Q7 cap indicates a problem in the audio section. If there is a change when tuning, it seems the IF may be oscillating.

Check deeper for errors. This is why I never advocate a total recap - too many chances for error. Once it works, you can change a part at a time to make sure you aren't screwing up.

Check that the B+ is adequate. You'll need a voltmeter for that. See if the ripple is excessive; you will need a 'scope for that unless you have a spare electrolytic capacitor to parallel the existing one. If the hum goes away, you need to fix the power supply.

One sneaky way to check the B+ is to run the radio, pull the power plug, then quickly short the B+ to ground with a screwdriver. Should get a major spark.