TU-8900 Help

I'm almost done with my TU-8900 and I ran into this problem. Pretty sure I seated the volume shaft onto the switch. Can anyone advise me where I went wrong and where to go from here?
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Apparently I needed to jam the rod harder onto the switch. I was concerned about breaking the switch, but it works fine now. Current problem is no audio and massive hum. Sounds like a bad solder joint somewhere. Guess I'll take it all apart again.