Hercules 2 vs Valhalla heat problems

I think that they both use the same high voltage stage. I would also say that the 15K power resistors fail a hell of a lot less than the caps do, in the Valhalla. 

Are the cap failures due to inadequate voltage spec of the caps or just simply becoz of their age ?

Well cap life is affected by a number of factors, how old the cap is, how close it is operated to its voltage rating, power pulses, ambient temperature, and I’m sure several more. 

No doubt about it the caps are operated near or over voltage which is why, when recapping, most of us increase the voltage rating of the key caps as well as the underspecced diode bridge. On the other hand, the Valhalla board came in somewhere around late 1981. So most of these boards in service have been recapped multiple times by now. 

I have no first hand experience with the Hercules, but I will bet that all of that has been corrected on that board since there are many, many, Valhalla’s in service and these weaknesses were known decades before the Hercules came into being.

Its interesting, Peter Swain, of Cymbiosis, probably the most respected Linn tech on the planet marginally prefers the recapped Valhalla to the Hercules on a strictly sonic basis. Having that 45rpm speed at the touch of a button seems a pretty cool thing and worth the price of admission though.