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John Bowers Active Control Unit: Seeking info and service manual

Hi HiFiEngineers

I have one of these preamps that appears to be unwell. I have no electronics experience, and the technician I took it to, says it seems to be impossible to disassemble so that the bottom of the pcb is visible. The top and side covers seem to be a single folded sheet which is easily removable. However, the rest of the case (bottom with front and back panels) is also a single folded sheet, with various pcb-mounted switches and jacks attached to it. It might be possible to rip components out of the board. but would be difficult to solder replacements into position. I have been assured that this will make it impossible to isolate the fault, without major surgery to the case.

So.....are there any arcane tips or tricks, magical incantations, secret levers or switches that could unlock this ancient and mystical device? Or was it designed to be disposable?

Even if I were able to expose the entrails, is there a service manual or schematic available that could be used to interpret the omens and portents thus revealed?

I seem to recall that it was quite fine-sounding, when it was working, but is it actually worth the struggle, perhaps removing the front (with glued-on faceplate) and rear panels with an angle-grinder?

Also....it has a 2-pin 'wall-wart/power-brick' box with captive lead. This has half a faded sticker which seems to mention a number of voltages, i.e. 220/240 V AC and 15-0-15 V AC. Does this mean the brick is merely a transformer? What could I replace it with? (One of the pins is wobbly)
Is 15-0-15 V AC the same as 30VCT? They seem quite rare.

The label says something like
Do not tamper with this unit. Lethal voltages internally.
?5VA Transformer (15? 115? 75? probably 15VA)
For? use only with John Bowers Active Control Unit 1
?ary : 220/240 V AC
?ary : 15-0-15V AC (I'm almost certain the 3rd number is 15)

The rest is illegible/missing.

Can anyone please help with documents, solid info or experience? I would be eternally in your debt for at least 5 minutes.

Thanks and Regards