On Tue, Feb 1, 2022 at 05:29 AM, Colin Herbert wrote:
According to the manual, C26 is supposed to be an Aluminium electrolytic at
50uF +100% -10% and 6 vdcw, whereas C27 and C28 are also Aluminium
electrolytics at 50uF +75uF - 10uF and 25 vdcw. All three were originally made
by Sprague. I realise that these would now be quite old (the manual was
printed in October 1975) but what would one use to replace them? Instinct
suggests that modern capacitors would probably better that those used in 1975,
but 50uF is a value that doesn't seem to exist these days.
Colin -
Generally if the above are radial power supply caps with white or silver-ish look, likely after 50 years, they are bad. Any modern ones will be physically smaller, and likely have a somewhat lower capacitance in reality (like -20% from what's printed on the outside) so I'd fit a 220uF or 330uF/10 V for the 50uF/6 V; for the 50uF at 25V, I'd use a 330 or 470uF at 25 or 35 Volts, usually you can't go wrong when going up in value five to ten times, especially since vintage caps, being physically larger, usually had lower ESR (when new, but no longer) than modern (physically smaller) caps. Since the set might have tantalum caps, check for those, the 1970-1975-ish parts can fail over time, might be smart to replace them while the set is already apart.
Steven
