Grundig TM819A help needed

[Tedzed1]

Thanks for the help so far everyone, rewired the valve socket, and now have life, sound is at a good level, but alas have got an incredible hum, it only appears on playback, but not on fast forward or rewind, it will vary with the volume control, but sounds similar to a 50Htz mains hum, at a good volume, the speakers are bouncing, but whatever is on the tape, plays at a decent volume.