(Topic ID: 293754)

System 11 MPU (B) Capacitor Question

By RGarriott

5 months ago



Topic Stats

  • 4 posts
  • 3 Pinsiders participating
  • Latest reply 5 months ago by Tuukka
  • Topic is favorited by 1 Pinsider

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#1 5 months ago

To give a little back story, i was installing a nvram on a pinbot. While lifting the old ram i broke the (B) capacitor that sets to the side of the U25 ram chip. According to the prints this is a .01mf 50v +54 bypass capacitor. Not really sure what the difference is to a normal capacitor?
Anyway i stole the (B) capacitor from my working F14 board at the U4 chip and placed it on the pinbot.
As you can see in the photo i replaced the capacitor at U4 with a ceramic .01 mf. This is different from what was in there as u can see at the U5 chip. The rest of the board has what appears to be glass encapsulated capacitors. I have seen boards with both kinds.

Is there a difference?

And when i placed the board back into the backbox and started it up I am now getting a mem protect error.

Anyone have a idea of what went wrong?

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#2 5 months ago

Simple "bypass" capacitor -- anything will work there.
Glass encapsulated versus conformal coated cap for a bypass capacitor was a matter of what was available when the board was made.

#3 5 months ago

So there would be no reason to find a glass cap to put in that spot? Only to keep it looking like the rest of the board.

#4 5 months ago

Yes. Just install a 10 nF capacitor and it will be OK.

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