Replacing capacitors (caps)

NeXT Computer, Inc. -> NeXT Black Hardware

Title: Replacing capacitors (caps)
Post by: eagle on May 29, 2009, 11:18:50 AM
Greetings, all.

I've done a few searches but didn't find anything on this topic.

Has anyone had to replace the capacitors on a NeXT cube or station motherboard?  My 5 motherboards are really old now (2x 68030-25 Cube, 1x 68040-25 Cube, 2x 68040-25 station) and I know they'll need to have the capacitors replaced at some point.  I just wondered if anyone had done it and had done a howto on it.

Thanks.
Title: Replacing capacitors (caps)
Post by: pentium on May 29, 2009, 11:41:26 AM
I wouldn't need to worry until they do finally fail.
Title: Replacing capacitors (caps)
Post by: helf on May 29, 2009, 12:30:27 PM
Some electrician told me good caps should last 25 years or more... so I don't think  should worry much :P
Title: Re: Replacing capacitors (caps)
Post by: cubist on May 29, 2009, 08:32:29 PM
Quote from: "eagle"I've done a few searches but didn't find anything on this topic.

Need to search harder.  In the NextDimension section, I wrote about some evidence of outgassing and can expansion.  Hasn't failed but I can imagine they will.  When the time comes, I'll just do a bit of SMD rework.  The boards, which were cutting edge in their day, look positively roomy now.
Title: Replacing capacitors (caps)
Post by: Ferrari-Dude on July 23, 2009, 09:28:39 PM
What kind of caps are they; Electrolytic, Mica, Mylar, Ceramic disc?

Generally speaking, electrolytic are really the only ones that have problems after a period of time.  

They usually contain an acid-based paste (electrolyte) on the layers of insulation material inside the can.  This tends to dry out over time and heat accelerates the aging process.

Also, as with any physical thing, some manufacturers are better than others.  Anything with *con in the name tend to be good brands.  So Nichicon, Chemcon, etc... will be a good choice.  Mallory also makes some great capacitors.

Look to see if the cans are bulging or warped.  This is also sign of dying or dead caps.  Try mouser electronics for replacement parts.  http://www.mouser.com

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