Recapping old tube amp

[indianajo]

Originally Posted by famousmockingbird

I was also looking at Sprague Atom (if I go the terminal strip route) and can't find info on them either.

Sprague atoms 1970 production are good for 25 years. No, they don't provide any data. I used to have the 1968 3000 page Sprague designer binder, but I lost it in a move.
Because modern rectifiers tend to short, I put a terminal strip in and put a resistor between the transformer and the rectifier. Also protects against oversize cap turn on surge. I've got 5AR4 rectifiers. 47 ohm 3 watt silicon coat wirewound is not big enough wattage- goes transparent when the surge hits it, then smells funny (but measures okay). Probably 5w is big enough, but I actually installed salvage resistors from a PCAT power supply, so don't know what wattage it is.

[trobbins]

It's unlikely that 47uF would be too much, given that electrol's, especially old ones, would have had at least 20% tolerance ratings.

A good learning curve is to measure the primary winding and secondary winding resistances, and determine the effective secondary side source resistance. Then check the 6AX5 datasheet for max capacitance allowable to see if you have more latitude in choosing values. The forum would assist if you are unsure.

There are techniques for tweaking your options, by adding series secondary resistance or a primary side NTC resistor, but if you don't need to go there then KISS.

[Ron E]

I heard an interesting story over the weekend, a comparison was made between a hotrodded (upgraded caps and boutique tubes) dynaco 70 and a stock one, and the stock one was preferred by a near unanimous vote. The hotrodder was mad.