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#1 2018-05-14 03:24:59

beebs
Member
Registered: 2018-05-14
Posts: 2

Re-capping 1989 Macintosh Portrait Monitor power board...

Hi all,

Found your forum doing a search about 105˚C vs 85˚C caps. 

I am re-capping the power board on a 1989 Macintosh Portrait Monitor.  Spent an afternoon with a magnifying glass, reading values off all the electrolytic cans.  Made my list and went to a parts place yesterday, about 25 miles away.  This particular shop doesn't let you pick your own caps, they're all "behind the counter"...so I gave them my list and trusted the ladies who were picking the parts to pick the right ones.

Got them home, and started in on the re-capping.  It was going smoothly for the first few, but then noticed some fairly significant can size differences between original and new caps, and started reading the rest of the tiny print.  I had specifically stated on my list that i needed ALL 105˚C caps...the ones that they gave me are nearly ALL 85˚C caps.  No wonder they were all different can sizes from the originals.

I was hoping that the 85˚C/105˚C thing wouldn't make a big difference, but after some googles and some reading, I figured out that it probably will.

I am guessing that since this is a hot-running CRT monitor, that I am going to need to go find 105˚C caps and re-do all the ones I've already replaced.  I was about halfway through it at about 2am when I realized the 85˚/105˚problem.  Of course, the shop where I bought them was "All sales final", so I'm out about $40 for the wrong caps.  Going to a different supplier tomorrow, one I know lets you pick your own parts.

Also, about 1/3 of the whole bottom of the board is enclosed in a black plastic bracket/cover/stiffener (pic att'd).  I've had to take the Dremel to some of it so I could reach the solder points on some of these caps.  I'm guessing that as long as I'm not structurally compromising it too much it shouldn't matter.  It looks like the flyback tranformer is somehow mounted to this black plastic covering THROUGH the circuit board, so I don't think I will be able to remove the circuit board from the cover. 

Wondering if there would there be any possible danger of voltage arcing over in the spots where I've had to Dremel out an opening for the soldering iron (especially in the area around the flyback).  Most of the places I've had to cut have been near open board anyway, but there are a couple that are going to need extensive cutting on that black plastic to reach.

Really didn't expect this to be such an ordeal.  Hopefully once I have the correct caps, it will go smoother.  If anyone has any experience working with the caps on the power boards of these Portrait displays, I'd appreciate hearing any observations/advice.

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This is one of two Portrait Monitors I'm gonna be recapping.  This one is actually a job for someone, the other one will be re-capping my own Portrait dislplay (which has been sitting in storage for 15 years or so).  Also about to re-cap two SE/30 motherboards using the little tantalum block caps.  Hopefully that will give both SE/30s back their sound capabilities.  TIA.

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#2 2018-05-14 18:53:00

mcdermd
Member
From: Corvallis, OR
Registered: 2014-05-12
Posts: 988
Website

Re: Re-capping 1989 Macintosh Portrait Monitor power board...

I'm not sure where you are located, but here in the USA most of us use Digikey or Mouser online. You can pick the right caps you want from a good brand name like Nichicon.


Daily Drivers: 27" iMac 2.8 GHz Quad-Core i7 (Late 2009), 21.5" iMac 2.7GHz Quad-Core i5 (Late 2013), 11" Macbook Air 1.6 GHz i5 (Mid-2011)
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#3 2018-05-15 00:32:36

beebs
Member
Registered: 2018-05-14
Posts: 2

Re: Re-capping 1989 Macintosh Portrait Monitor power board...

I'm in SF Bay area (Alameda), and just figured I'd visit the local parts places that an Apple guy recommended, which were down in the South Bay area.  I went to Berkeley this morning to visit a closer shop I'd been to before, but they are closed until Wednesday (a little mom-n-pop place, they close when they feel like it).  So I drove back down to Santa Clara today and got most everything at the same two places I went Saturday.

Realized when I looked at my list that the 105˚ notation was on the other side of the paper I'd folded in half, so I can't really blame the folks at the parts house.  Learning experience all around.

And as I was staring at the board last night, wondering how i was going to get to some of these solder points, I finally realized that the flyback was attached via screws that went all the way through the board and down into the black plastic cover, so I was able to get the board separated from the cover, and can hit all the solder points now.  There are several "pop clips" around two edges that will let the board come semi-loose, but those flyback screws and one more screw (about midway down one side) are what was holding it.

And yeah, with traffic being what it is here in the Bay Area, I left this morning at 11:15 and just got back about 15 minutes ago...simply to not have to fight the traffic is a great reason to go with Mouser.  And they ship fast, as well...ordered a metalized paper line-filter cap for a 128k Macintosh from them and got it within a couple of days.

Update 5-15-18

Well, I got it finished, and it looks marvelous.  Pretty amazing difference from what it looked like before.  The adjustments sequence went MUCH smoother with the freshly capped board.  I was able to get the geometry correct in just a couple of tries.  And there is room to spare for future adjustments on those surface-mount adjustment pots.  They were pegged completely before, now there is room to adjust.  This makes me excited for recapping my OWN Portait, as well as my Two-Page Monochrome Display.  Of course, cameras don't "do" CRTs very well, but out of three different cameras, a little Canon point-and-shoot gave the best pics...the rest all had black diagonal bars in various places across the photos.

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Last edited by beebs (2018-05-16 04:22:28)

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