[Keng]

OK. I have downloaded the bunch of schematics for the various model 60s. None of which show three filter caps.

Looking more closely at your photo, it looks as though the 4-pin socket for the 80 rectifier must be the one at the bottom of the photo between the bottom Atom and the blue or black electrolytic cap.

Also, looking more closely at your photo, it seems that the upper-left Atom cap's + lead is not connected to the tube-socket's filament pin, but to a lug above that. In any case, none of the various schematics for the Model 60 shows more than 2 capacitors with a value as high as 8 mfd.

Secondly, yes capacitors in series act like resistors in parallel: the total value is less than the value of the individual component. Two equal value resistors in parallel equals 1/2 the value of either and the same goes for caps in series, assuming their ESRs are equal.

Thirdly, if it was me, I would replace the original capacitors with ones of the same value, or as close as one could get. As Terry says, raising the filter capacitance significantly will raise the HV in almost all cases.

Fourthly, can you read what is written on the masking tape that is on the dark blue or black capacitor? If so, what does it say? Learning what is written there MAY give us a clue.

Ken