How NOT to fix a photomultipler power supply

My MacBeth RD100R (Reflection Densitometer) was  wonky.  I dug out my ancient Eico VTVM -- it will read to 1500 Volts unlike my Beckman and HP multimeters -- and found that the HV just wasn't where it should have been.  I replaced the 1B3 rectifier with another, and reassembled the unit. 

All was working, or so I thought.  When trying to adjust the linearity potentiometer, apparently too much current was drawn across the multiplier capacitor.  The thing went off like a shotgun shell, spewing ceramic pieces into the case.  The result can be seen above.

The MacBeth RD100R uses a 931B Photomultipler Tube.  Hammamatsu has a lot of information on their website.