Bringing a Mac Plus back from the dead!

[bibilit]

Are we speaking about the Line capacitors or interference suppression capacitors  ? (C33 and C36) those are 4700 pf 250 volts.

http://www.justradios.com/safetytips.html

I will have a look at the 4 diodes used to built a bridge rectifier as well.

 

[JNizzle]

Are we speaking about the Line capacitors or interference suppression capacitors  ? (C33 and C36) those are 4700 pf 250 volts.

http://www.justradios.com/safetytips.html

I will have a look at the 4 diodes used to built a bridge rectifier as well.

We're talking about C33 and 36. I'll take a photo of what I replaced, and what I replaced these caps with.

I'll post the links to imgur, as all my pictures are coming out huge for some reason.

Caps I replaced:

https://i.imgur.com/VOwJRCY.jpg

What I replaced them with:

https://i.imgur.com/PaH0Iga.jpg

I tested all the diodes in the rectifier, I'm getting about 2.1mV in one direction and about 4.6mV in the other.

 

[IlikeTech]

Those are safety caps, and they probably should have been changed with proper replacement safety capacitors.  You might want to change them out again.

 

[LOOM]

The original cap you replaced have cracked the same way as mine had. I replaced them with a KEMET PME271Y Series, DigiKey part number 399-5411-ND. These look the same as the originals. I have a euro mac plus, so these are rated 250VAC.

 

[LOOM]

Okay, noted. I will replace those caps as I just checked, and they do look a little old and cracked.

Also, I was under the impression that any capacitor could be replaced by one with the same capacitance, but any HIGHER voltage, as the voltage on a capacitor is only it's minimum voltage.

Correct me if I'm wrong.

I'm no expert in this so I've waited for other to reply you, but here is my understanding of this:

They can work, but if the capacitor have a lot higher voltage rating than the original part then they can have trouble forming.

Lower voltage caps also have lower ESR, important in switching power supplies.

Cheap general purpose capacitors usually have higher ESR and shorter (shelf) life (in hours) than the more expensive ones, so I always try to buy the one that lasts longer when I want to recap. I usually stick to KEMET, Nichicon or a brand type.

Just an example, the KEMET ESY series is built for switch mode power supplies, and up to 5000 hours