Gus,
I don't know that particular unit (is it quite old??), but here's a few presumptions:
If it's a graphic equaliser in a 1U chassis, the chances are that it's an EQ based on op-amps. The older tube and transistor units relied on inductors- op-amps allowed the gyrator circuit to be realised- doing away with the inductors. A 1U chassis wouldn't allow much room for inductors in a multichannel EQ.
The easiest way to run op-amps is using a split +/- supply. So I'm guessing that no matter what, it'll be a +/- supply. The voltage- well, that will
probably be +/- 15V. Could be 12, or 18, or even 24. But this can probably be easily changed- second presumption- 78/79xx voltage regulators. These can be easily swapped out and replaced with different values (obviously depending on transformer secondary voltage- but if you've got a +/-18V regulator circuit, you can pop some 15V regualtors in with only slightly greater heat dissipation...)
Also, I reckon the PSU will allow access to the secondary of the power transformer- so you will be able to do the voltage-multiplier phantom trick.
Just my hunches! (don't blame me if it's a +ve ground, -1kV @1mA max PSU
)
:wink:
Mark