Greetings,
I have an old Lexicon Vortex. The PSU output says 9VAC@1A.
Because I’m paranoid about blowing it up I’m asking if it should be ok to plug it in to my pedalboard power supply which has 1 AC output labeled 9v AC 800mA.
I think it should be ok but would 800mA be enough?
The unit is a little noisy and I was thinking powering it from the same supply that powers the pedals might reduce noise. But then it ends up being patched into a mixer after being fed by the pedals. I don’t think it’s a ground loop noise issue but I thought a little test might confirm.

If the supply is 9V and AC you won't blow the FX unit up. It might be quite happy with 800mA... but equally, it might not. You'll have to try it and see.

It will probably work - for a while. It may only work for a few hours or many years. We can't really say without knowing how well protected the power supply is and how much current the Lexicon really takes. Given that the service manual for the Lexicon suggests using a variac to bring up the supply voltage slowly, the unit is probably tolerant of low input voltages. One other thing I noticed was that the analogue circuitry runs on lower supply voltages than normal so will be easily overloaded. Check that you are feeding it an appropriate level which will probably need to be lower than normal line level.

The Lexicon power supply is probably double insulated without an earth so I would be surprised if using a different power supply would make a difference to the noise.

Fortunately there is an input knob on the unit. And, yes, I’ve got it turned quite low. I have the original paper manual. I’m surprised you found a service manual.
Thanks all for the thoughts.
I may end up with one less wall wart in the octopus under my desk.