The story that "more is better" is almost always partly true.
Partly.
The voltage rating is important.Your description of "strung together" suggests that they have been combined in series, or maybe series-parallel. Raising the voltage rating probably won't offer any useful result.
Using a cap double the original capacitance can put stress on the power switch from the power-on surge. Charging the filter caps up from dead empty will create a surge current that's in proportion to the capacitance. Adding a surge resistor between the transformer's HV winding and the HV rectifiers to limit the additional peak current is the quick-and-dirty way, if there is room for it. The surge rating of your HV rectifiers will be the guideline to calculate the resistance value needed. The current drain the tubes pull from the HV will dictate the wattage rating the resistor will need, once you choose the resistance value.
The 'step start' circuit used in the large Ameritron tube amplifiers will save your power switch from surge damage. Typical problem is that adding larger filters causes the contact points in the power switch to spot-weld in the "ON" position so that it no longer turns off properly. That's what happened in our Dentron MLA2500 when I doubled the capacitance of the HV filter caps. Seems to happen in D&A Phantom amplifiers, even with the stock-size filter caps. Learned to use a two-circuit 20-Amp per-pole switch with both sides wired together in that model.
We have been buying chinese step-start circuit boards on Chinabay when we need to retrofit this feature in a large amplifier. The home-brew or "bowl-box" amplifiers almost never come with this feature in them.
The small recitifier diodes found in some older sweep-tube amplifiers may look like a 1-Amp rated 1N4007, but some of them were a now-obsolete "2.5-Amp" rectifier. Same phyiscal size, more or less, but with the higher rating. That's what D&A used for a lot of their amplifiers. We standardized on the 3-Amp rated 1N5408 to replace those. If you had trouble using that one, I would suspect operator error, rather than blame the parts. I buy 1N5408 by the thousand, using them in everything from Pride DX300 power-supply boards to Browning radios.
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