Re: DAC 90A Smoothing Capacitor replacement
Sam's right. However...
In the DAC90a the current is less than half the maximum for the UY41 rectifier valve, so it has an easy life anyway.
Increasing the reservoir capacitance will indeed increase the peak current through the valve (bigger peaks of shorter duration), but not massively. Manufacturers put a limit on the reservoir capacitor for other reasons - limit the switch-on surge if the valve is hot; limit current surges if the mains fluctuates, etc.
Adding extra capacitance for 10 minutes evaluation really won't hurt (I've done it!) though don't repeatedly switch off and straight back on, or operate heavy machinery from the same supply mains, while you have your extra reservoir. But if you temporarily throw lots of uF's at the radio, and the hum hardly changes, you know the HT rail is then blameless and you can look elsewhere.
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