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I'm repairing an old 5" reel audio player from the 70s and this capacitor is on the small board that attaches to the switch that selects between track 1/2 or track 3/4. I don't recognize the markings on it and am unsure what order to even read them in. It seems to be on the top row ".01," with a rather large space between the 0 and 1. And then we have "8Y .M" on the bottom. Or, am I supposed to read this left to right as ".0 8Y, 1 .M?" Is this one of those odd Y capacitors (which would kinda make sense, filtering out line noise to the tape heads)? Sorry for the rough quality of the image, as it was hard to get a clear shot.

capacitor image

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    \$\begingroup\$ i would guess that the .01 means it's 0.01 μF, or 10 nF, but that's very much a guess. Are you sure this capacitor's bad? If not, try taking it out of the circuit and measuring it. If it is bad, see if you can't find an identical or similar capacitor elsewhere on the board that you can measure. \$\endgroup\$
    – Hearth
    Commented Aug 29, 2023 at 4:11
  • \$\begingroup\$ The capacitor does not look like it is doing anything that would require it to have Class Y safety rating, as it does not look like a mains power supply circuit or other high voltage circuit. But remeber, you are the one repairing the device, you must know what you are doing, and you must keep in mind that if that capacitor really has some specific Class Y rating, replacing it with unsuitable capacitor in a mains powered device means the device can become a shock hazard and kill people, so you can't randomly replace parts. \$\endgroup\$
    – Justme
    Commented Aug 29, 2023 at 4:48
  • \$\begingroup\$ There are only 6 caps on the switch board and this is one. I am not sure it is bad, but I'm pretty sure some of the caps are and this is the only one I couldn't ID. I wanted to avoid removing them more than once and just replace them all, if possible, since caps are cheap enough. Track 1/2 plays a few seconds and then audio fades out unless the switch is cycled to 3/4 and back, and then you I get another second or 2. \$\endgroup\$
    – rbudrick
    Commented Aug 29, 2023 at 4:49
  • \$\begingroup\$ I think some caps are just losing charge. Tracks 3/4 play fine. It is less likely this one is bad than the other 5, I'm thinking. Mostly, I just want to be able to replace it if it is and be able to identify a modern one if when I replace the 6 other cylindrical caps it still doesn't work right. I figured it's nearly 50 years old anyway and probably wouldn't hurt. \$\endgroup\$
    – rbudrick
    Commented Aug 29, 2023 at 4:50
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    \$\begingroup\$ @rbudrick Ceramic capacitors rarely go bad. And even if it did, it would be likely that a broken ceramic cap would cause the symptoms of your device. Likely the caps are not the fault. Randomly deciding to replace all capacitors without debugging what really causes the problem won't fix the device. It might be the switch itself that needs cleaning or is just worn out so it does not keep the circuits powered. \$\endgroup\$
    – Justme
    Commented Aug 29, 2023 at 5:48

1 Answer 1

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Looks like a 0.01uF (10nF) dipped polyester (Mylar) capacitor, probably rated at 50V or 100V. Unlikely it is bad at all, I suggest not tampering with it unless you have good reason.

The cylindrical aluminum electrolytic capacitors may be worth replacing. They operate on a completely different principle and do tend to dry out and decrease in performance (increase ESR) over time because they contain liquid electrolyte.

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  • \$\begingroup\$ Thanks, folks. I agree it is unlikely, but I just wanted to know, if it comes to that. Definitely going to do the cylindrical ones first, as those go bad often enough. The switch has been thoroughly cleaned and contact is definitely being made. Sphero, thanks for the answers on the values. Can you tell me what the 8Y means? Is the M for Micro, or Mylar? And why the decimal before the M? Thanks again! \$\endgroup\$
    – rbudrick
    Commented Aug 30, 2023 at 2:46
  • \$\begingroup\$ M could be +/-20% tolerance. But there are often some markings which are not of much meaning to the prospective repair technician on such parts. Manufacturer model numbers (likely long-gone), date codes and such like, so I would not be too concerned. On the other hand, replacing the part with the wrong construction (eg. ceramic vs. film) could conceivably affect the sound even if the nominal value and voltage ratings are the same. Measuring and dissecting a good part would tell you more, but then you'd have destroyed a perfectly good part. \$\endgroup\$
    – Spehro 'speff' Pefhany
    Commented Aug 30, 2023 at 4:16
  • \$\begingroup\$ Thanks, Spehro, that helps a lot. Since this is my first time here, it's not letting me upvote your original answer because I don't have 15 reputation yet. In any case, it is much appreciated. Thanks to all else as well! \$\endgroup\$
    – rbudrick
    Commented Aug 30, 2023 at 4:43
  • \$\begingroup\$ @rbudrick You're welcome. After an appropriate time has elapsed you should select whichever answer best answered your question, if any did. \$\endgroup\$
    – Spehro 'speff' Pefhany
    Commented Aug 30, 2023 at 4:50
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    \$\begingroup\$ Ah, is that the green check? If so, it did indeed let me choose that. Sorry, newb here, heh. \$\endgroup\$
    – rbudrick
    Commented Aug 31, 2023 at 23:47

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