Circuit from an old Bass amp (Peavey TKO 115 BW, not sure of the year but I think mid-90s) that previously had a pretty bad 60 Hz hum to it. Someone on some forum somewhere suggested replacing the zener diodes on the low voltage supply, and I figured i'd give it a shot (whether or not this was a good idea remains to be seen). I got some replacement diodes that matched the part number, but now instead of the voltage across each diode reading 16 V, it reads about 0.9V, which I guess does technically stop the hum in the sense that it is now making no noise at all.
At first I thought I put them in backwards, so I flipped them around, no change. Then I figured I'd fried the first set, so I put in two new ones which still didn't work. I feel like there's gotta be something I'm missing here, but I'm pretty new to electronics so I'm struggling to figure this out.