Difficulty Identifying a Component from Circuit Board

[RamblinRedneck]

I want to start out by saying I am not experienced with the internals of electronics, so I will probably sound stupid. I was recently given an 1971 vintage sound system consisting of a Sansui 800 solid state amp, a Pioneer turntable, and a Teac A-2050 reel to reel player. I have used the amp as a receiver for a while now, and I finally cleared room for the reel to reel machine. After I hooked everything up, I fired it up, and the sound was pretty good aside from needing to clean the heads. The problem started about 30 minutes later when it started smoking. It still worked when I shut it off. I removed the back and found what I believe to be a capacitor smoking. I very carefully de-soldered it from the board, but I can't figure out what I need to replace it with. The markings do not match anything I have found online thus far, and I really hope someone with more expertise in this can help me. I will attach a picture, but in case it is not clear, the markings read:

400AC
0.1 M

I appreciate any help I can get.

 

[mmckenna]

Not uncommon for capacitors to dry out with age and do this when powered up.
Hard to tell from the photo, but looks like a capacitor.

 

[RamblinRedneck]

That was kind of what I was thinking. I tried googling the markings on it and came up with nothing, then I tried to research how capacitors are marked and ended up more confused than ever. I want to order one of those sets that has several different rated types, I am sure I will probably need more than one, but I can't for the life of me figure out what the markings mean on this thing, so I don't know what to order. I am a much better lawn mower mechanic.

 

[pro92b]

The photo is too out of focus to be any help. The markings you listed suggest it is 0.1uF 20% 400Volts AC, maybe. Is it connected to the AC line?

 

[jonwienke]

400AC is probably the voltage rating--400VAC max.
0.1M would be the capacitance rating, probably 0.1 microfarad.

The photo is too blurry and there is no scale reference to tell if those values are plausible.

 

[RamblinRedneck]

Honestly, I couldn't tell you what it's connected to aside from saying its on a small circuit board. This is really out of my element. I tried to get a good picture, but that's hard with a webcam. I will try to get a better one. There are several identical ones in a little cluster, this was the only one busted open and pouring smoke though.

 

[pro92b]

Understand that if it is connected across the AC line, there are certain safety certifications that the replacement part should have. If in fact the original part is rated for AC voltage rather than DC, that implies it needs to be a safety certified component.

The link below provides a discussion of the various classes of capacitors for direct connection to the AC line. It also identifies the safety agencies that approve these types of components.

https://www.allaboutcircuits.com/technical-articles/safety-capacitor-class-x-and-class-y-capacitors/

 

[RamblinRedneck]

This is the best image I could manage with that I have on hand. It's blurry, but you can somewhat see the markings.

 

[prcguy]

If the part was across the AC line as a filter, then the Teac should still work when plugged in. Have you tried it with the part removed?
prcguy

 

[RamblinRedneck]

No, I honestly haven't. I have the small board that goes on hanging loose just suspended by the wires. When I get a chance I will put the screws back in it and try.

 

[mmckenna]

It's possible that if this capacitor failed, there are very likely others that will too. You may need to look at replacing all the capacitors in the power supply.

When I was a kid, my grandfather gave me an old kit shortwave radio he'd built. It had been sitting for a long time and several of the capacitors in the power supply had dried out. It didn't smoke, yet, but the noise was pretty bad. He showed me how to replace the capacitors and we had it working again.

 

[K5MPH]

Could you take a photo of the board itself.....

 

[RamblinRedneck]

Sure, I will get one as soon as i can. I was thinking along the lines of having to replace them all, I just have no clue what to order. I see the 700 piece sets on Amazon, but I don't know what the specs are, so I dont know what to order.

 

[RamblinRedneck]

Here is a picture of the board, you can see the holes where I removed the old capacitor.

 

[RamblinRedneck]

I connected the power and turned it on, and just as suggested, it works.

 

[mmckenna]

That looks like it's a module that controls motor speed/direction.

 

[lmrtek]

Only oil filled electrolytics "dry up"
...........
That is not an electrolytic.
..........
The caps pictured for example are likely just there to suppress
the arcing of the relay contacts.
..........
Just like when REAL cars used ignition points, they also had to have
a condenser across the contacts to prevent arcing from destroying
the contacts prematurely
..........

 

[RFI-EMI-GUY]

I would bet that the other relays have same type value capacitor across their contacts. Most likely there was a lot of inductance and the voltage rating of the cap was exceeded. No special reason to worry about the others like it.. When you powered this up you didn't use an isolation transformer or variac by any chance?

 

[RamblinRedneck]

I would like to pretend I know what that means, but I honestly do not.

 

[krokus]

That looks like it's a module that controls motor speed/direction.

That was my thought, too.

Try finding someone that still fixes these things, and ask them if they would sell you the part. There should be an identifier on that board, for that part. It should be Cxxx, where the xxx is a number. (That can be looked up in the parts listing of the service manual, and should give the values for that part.)

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