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Capacitor advice

R

radiotron_

Member
Recapping an old Sanyo channel master portable 6 transistor radio, has real low volume so I figured I’d recap it. I’m inexperienced in recapping things and got this for cheap, so it would make a great starting project-I already know how to solder things. it’s got about 5-6 of these green plastic 30 uf 6v capacitors in it-Cant find any replacement caps anywhere, closest is a 33 uf, but if the voltage rating is too high it may be too large of a cap to fit under the cover. Thoughts? The original caps are about 14 mm tall.
 
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Tons of choices there. A quick poke at Mouser looking at 33uf radial lead (both sticking out one end) caps in 10-25v gives me 113 options in-stock, none of them taller than 12mm. I think you'd have a hard time finding caps that are taller than the originals honestly.
 
From what I've seen most modern electrolytic caps are smaller, sometimes significantly, than the old stuff. Depending on one's definition of old, of course.
 
gadget73 said:
Tons of choices there. A quick poke at Mouser looking at 33uf radial lead (both sticking out one end) caps in 10-25v gives me 113 options in-stock, none of them taller than 12mm. I think you'd have a hard time finding caps that are taller than the originals honestly.
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33uf will work? I heard it should be no more than like, .25 different from the capacitance of the old one, so here I am straining to find exact capacitance or a few points off.
 
Really depend what they do and what charge them.

If it's a DC filtering capacitor, the only reason to not increase like crazy is they need more current to charge, and that stresses a rectifier, they are hungry when not charged at all and receive current, but solid state diodes are not fragile as tube rectifiers, you must be very careful not to add too much capacitance in front of a tube rectifier, but solid state rectifier diodes doesn't really care. (Doesn't really care not mean they do not care at all, but it's not as critical as a tube who tolerate between a few to a few dozens of microfarads).

In a transistor radio, you could even use 100uf, and only risk it sound better.

if it's use as an interstage coupling capacitor for low frequencies filtering, you should not to increase if you don't know what you do.
 
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If those are epoxy sealed they are not your problem, as it's very unlikely they have leaked. But if you want to replace them, 33uF 10 or 16V is fine, 25V is sort of overkill.

The "standard" values of capacitors have changed over the hears, 30 and 50 used to be quite common and now you will only see 33 and 47 uF. Not enough difference to matter. New ones are likely to be closer to the marked value than the old ones were when new.
 
radiotron_ said:
33uf will work? I heard it should be no more than like, .25 different from the capacitance of the old one, so here I am straining to find exact capacitance or a few points off.
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Electrolytic caps are often 20% or so tolerance, 33uf is only 10% off so its quite probably still within original specs. Generally speaking if you keep within 10% you won't have any problems. These things aren't high precision.
 
Alright, will do. Any ideas what the problem could be other than the caps? It’s real low output when powered on, seems to be receiving stations just super quiet.
 
could be a lot of things, but without some testing its hard to say. Bad caps, off value resistors, bum transistor in the audio amp section, a seized up speaker. Caps are sort of the low-hanging fruit just because they are often problemattic. Since it tunes OK but just seems to have weak audio, I'd probably try changing just the caps in the audio amp section first just to limit the variables. If you have a schematic or at least a model number, figuring out which those are would be fairly easy. If its only 6 transistors there just isn't that much going on inside this thing.
 
avionic said:
Does it have fresh batteries ?
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yep. Been tested with all new batteries… I got the replacement caps, by the way, which side is negative/positive on the old ones? One lead has a tiny black dot, like a sharpie mark, on each cap… guessing that marks the negative end?
 
radiotron_ said:
guessing that marks the negative end?
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Look closely at the black line . Usually the black line indicates negative. But.... I have also seen where the black line indicates positive. If positive the black line will marked with a plus mark (+).
 
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