Hi all, I have a McIntosh C32 solid state preamp that was unused for years. Plugging it in recently, the preamp has a "rushing water" sound with no input signal, and I suspect at least the electrolytic caps need replacing. My questions to you all are: (1) many electrolytic caps look to be common Nichicon electrolytics -- is replacing them with film caps worth it or will it cause problems? (2) There are some pill-shapped brown caps that I guess are ceramic caps -- do they go bad like electrolytics and should I replace them (and with kind: ceramic, others)? (3) There are some reddish brown cylindrical (I guess) capacitors marked "10/40 EKU K2" with "ROE" in a box, and also "10/63 EK J5" with "ROE" boxed -- what do I replace these with? Thanks.
Doesn't sound like electrolytics. Is the noise equally in both channels?
Phono or line?
(1) may be worth it sub-1µF, otherwise tends to create an unsightly mess (not to mention parasitic coupling).
(2) No, not usually.
(3) Inspect these Roederstein caps carefully, they have a reputation for developing cracks, in which case they would probably be toast. Otherwise they'd quite probably still be fine. The best replacement depends on what they are used for (consult schematic if in doubt), but I'd guess some Panasonic FCs or something would be OK. These are 10µ / 40 V and 10µ / 63 V, respectively. Modern types are likely to be smaller, I'd just use a higher voltage rating to compensate (within reason).
Unusually high noise may very well be electrolytics if one was used to filter a zener and now some critical supply is rather more noisy than it should be. Though the question would be how to improve regulator noise or PSRR if it's that easily audible, another question worth examining the circuit for.
(2) No, not usually.
(3) Inspect these Roederstein caps carefully, they have a reputation for developing cracks, in which case they would probably be toast. Otherwise they'd quite probably still be fine. The best replacement depends on what they are used for (consult schematic if in doubt), but I'd guess some Panasonic FCs or something would be OK. These are 10µ / 40 V and 10µ / 63 V, respectively. Modern types are likely to be smaller, I'd just use a higher voltage rating to compensate (within reason).
Unusually high noise may very well be electrolytics if one was used to filter a zener and now some critical supply is rather more noisy than it should be. Though the question would be how to improve regulator noise or PSRR if it's that easily audible, another question worth examining the circuit for.
Thank you both for your inputs! Hopefully I can find time to start replacing some caps/investigate more this weekend.
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