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  1. #1

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    Default Colour Classic - Analog Board Repair

    Hi MacTalk,

    It certainly seems as though Colour Classics are becoming rather popular around here. I have one of my own, but it needs some fairly extensive repairs to make it work again.

    One of the large capacitors in the centre of the Analog Board has leaked and corroded two of the surrounding resistors, both of which look fairly charred. One of them has corroded through the solder joint holding it to the board, and when testing it with a multimeter, it reads open. I intend to replace these components and recap both the Analog Board and Logic Board at the same time.





    I can't tell what ratings those resistors should be though. Almost everyone I've asked with a Colour Classic has also found the colour bands burned off, and some probing with a multimeter gives sketchy results at best. From what we've been able to gather, RL62 (charred, on left in picture) is a 41 Ohm resistor, but on two machines we've checked, this component reads 48 Ohms. The second resistor, RF11 (charred, on right in picture), measures 390 Ohms on one machine, but this is the one that reads open on mine, so I can't verify it.

    I'm attempting to find out what the coloured bands on these resistors are. If anyone has a Colour Classic Analog Board around or feels like taking a few snaps of their own board, it would certainly help a lot.


    Cheers,

    ~ Michael

  2. #2

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    This scares me. Our little Macs seem to be self-destructing at an increasing rate, and faster than I'm able to repair or maintain them!

    I mean, I knew the caps on the LB's are notorious for failure but we're starting to see other components degrading now. Unfortunately some components cause more damage than others as they fail, as we can see here. I guess for all of the components, it's only a matter of time, right?

    If I get around to it in the near future, I'll open up my Colour Classics, even if only to inspect for similar damage. I'll take some photos or measurements if I think they'll help.

  3. #3

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    Quote Originally Posted by macman142 View Post
    I mean, I knew the caps on the LB's are notorious for failure but we're starting to see other components degrading now. Unfortunately some components cause more damage than others as they fail, as we can see here. I guess for all of the components, it's only a matter of time, right?
    It looks like these resistors have failed because of the electrolyte spilled from that capacitor, or the added stresses placed on the circuit by the failure of that capacitor at least. Other components can and probably will fail, but I'd chalk this one up to collateral damage.

    Someone from the #mac68k IRC channel graciously took the Analog Board out of his Colour Classic a few moments ago and took a photo of these resistors.



    The readings are as follows:

    RF11 - Orange, White, Brown, Gold - 390 Ohm, 5% Tolerance (Measured 390 Ohm)
    RL62 - Yellow, Violet, Black, Gold - 47 Ohm, 5% Tolerance (Measured 47.5 Ohm)

    These are consistent with other measurements I've seen around, so I'm fairly confident these are the values for these two.

    I've also started compiling capacitor lists for both the Analog Board and Logic Board, which are about 98% complete with the exception of a couple of unmarked capacitors (at least I think they're capacitors) on the Analog Board.


    Now to price these up and see what the total comes to...


    Cheers,

    ~ Michael

  4. #4

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    Is Element14 still the go-to for this stuff?

  5. #5

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    I haven't used Element14 before, but I had intended to use them for this one.

    I did have a contact there that I had planned to consult with on this one, but it seems Apple Mail erased their messages when the mail database corrupted last year, so now I'm attempting to find their email address again.

  6. #6
    Oldmacs's Avatar Oldmacs is offline MacTalk Writer

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    Quote Originally Posted by iMic View Post
    I haven't used Element14 before, but I had intended to use them for this one.

    I did have a contact there that I had planned to consult with on this one, but it seems Apple Mail erased their messages when the mail database corrupted last year, so now I'm attempting to find their email address again.
    Sorry to go complelty off topic- but would you recap a few boards at a price? I need eecapping done and I can't do the small capacitors - they are just too small !!! No worries if not
    Plus, IIci, IIsi, LC, LCII, LC III, CC, LC475, LC630, Centris650, 6100, 8100, 5260, 7220, 7600. PB: 100, 150, 160, 165, 540, 190, 5300, 1400. Lombard, iMacG3, iBookG3, iBookG4, PBG4, eMac, iMac G4, PMG4, MiniG4, iMacG5

  7. #7

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    I've had some experience with soldering small connections (think iBook boards), but normally on my own stuff that I don't mind breaking if I stuff it up. I did manage to do a successful recap of a Macintosh Classic Logic Board, but since the board was already somewhat corroded, it was fairly messy.

    Perhaps I could attempt a recap of this Colour Classic board first to see whether my tools (and my skills) are up to scratch, and if all goes well, we could look into it?

  8. #8
    Oldmacs's Avatar Oldmacs is offline MacTalk Writer

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    Quote Originally Posted by iMic View Post
    I've had some experience with soldering small connections (think iBook boards), but normally on my own stuff that I don't mind breaking if I stuff it up. I did manage to do a successful recap of a Macintosh Classic Logic Board, but since the board was already somewhat corroded, it was fairly messy.

    Perhaps I could attempt a recap of this Colour Classic board first to see whether my tools (and my skills) are up to scratch, and if all goes well, we could look into it?
    That would be great!
    Plus, IIci, IIsi, LC, LCII, LC III, CC, LC475, LC630, Centris650, 6100, 8100, 5260, 7220, 7600. PB: 100, 150, 160, 165, 540, 190, 5300, 1400. Lombard, iMacG3, iBookG3, iBookG4, PBG4, eMac, iMac G4, PMG4, MiniG4, iMacG5

  9. #9

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    I've repaired the Analog Board successfully, so the CRT now works and is stable and flicker-free.

    Unfortunately the Colour Classic still doesn't work right. I took the Logic Board out and despite the electrolyte that had spilled around the caps being cleaned off, the small amount that has leaked below the caps has corroded through two of the solder pads. I can trace them to ground, and if I run some wire between the capacitors and the ground points on the board it powers up and runs, but I can't solder the capacitors down.


    I'm considering looking for a Macintosh LC 520/550 board or another Colour Classic board. The LC boards are probably slightly easier to find.

  10. #10

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    Sorry if this is a stupid suggestion but can you neatly glue the cap down with a hot glue gun and follow the damaged pads trace back to wherever it goes and run a wire between the two? Seems like a respectable repair to me? A less obvious repair than an LC LB swap anyway.

    Regarding the LC575 board, I'm not convinced its really worth upgrading now it's of this vintage, just my opinion though. It's not like we work a CC to capacity these days (or rely on them performing) but more than anything I think it just annoys me when the I/O cover is missing because it no longer fits... I suppose 10MB RAM in the CC could be limiting before anything else... I dunno, I'd rather see a slower original machine than a altered one for a bit more RAM and a few MHz. Does the resolution increase add any strain on the CRT? Again, I don't really know, just guessing.

    EDIT: oh yeah and after all that rambling of mine, well done with the repair! P.S. we require more pics now it's working

  11. #11

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    Quote Originally Posted by macman142 View Post
    Sorry if this is a stupid suggestion but can you neatly glue the cap down with a hot glue gun and follow the damaged pads trace back to wherever it goes and run a wire between the two? Seems like a respectable repair to me? A less obvious repair than an LC LB swap anyway.
    I've been able to do something a little cleaner still. I soldered the capacitors down where they were supposed to be with a couple of modifications. The capacitor closest to the edge connector is soldered directly to ground. Two areas of copper on each side of the damaged pad are connected directly to ground, so I scratched back some of the laminate and soldered the capacitor on an angle to connect it to the copper instead.

    The other capacitor was also soldered to ground, but didn't have an area nearby to connect it to. Some of the trace was left, but I wasn't confident in relying on that connection alone. So in this instance, I soldered one side of the capacitor to the intact trace (connected to VCC on the 68030) and the other side to what was left of the trace on the board. Then I ran a wire between this side of the capacitor and another unused ground point on the board.

    The other capacitors had intact traces and were soldered in normally.


    Quote Originally Posted by macman142 View Post
    Regarding the LC575 board, I'm not convinced its really worth upgrading now it's of this vintage, just my opinion though. It's not like we work a CC to capacity these days (or rely on them performing) but more than anything I think it just annoys me when the I/O cover is missing because it no longer fits... I suppose 10MB RAM in the CC could be limiting before anything else... I dunno, I'd rather see a slower original machine than a altered one for a bit more RAM and a few MHz. Does the resolution increase add any strain on the CRT? Again, I don't really know, just guessing.
    I believe that with an LC 520 or 550 board, the I/O cover can be installed since the ports match up. The LC 575 board is somewhat different though. That's what I've heard at least.

    I also know that at least the 575 board requires either the VGA mod to allow the CRT to run in 640 x 480 mode, or a software modification to enable 512 x 384 resolution. I don't believe that increasing the resolution through the VGA mod stresses the CRT as such, but I would imagine that it would further stress the Analog Board, which isn't something we want to do with the age of these boards.

    Quote Originally Posted by macman142 View Post
    EDIT: oh yeah and after all that rambling of mine, well done with the repair! P.S. we require more pics now it's working
    The complete repair hasn't been performed yet, still a lot more to be done on the Analog Board side, but I have a few pics that I can share.





    Logic Board

    The second and third photos show close-ups of the capacitors that had to be installed with a couple of modifications.






    Cheers,

    ~ iMic.
    Last edited by iMic; 15th February 2015 at 01:38 AM.

  12. #12

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    The Analog Board restoration is complete!




    I've replaced 39 capacitors across the board, along with the two burned resistors. Some solder joints on the underside of the board looked rather sad, and I've cleaned those up and braced up a couple of pads that were starting to lift in high heat / flex areas as well. I went over the yoke connector with fresh solder and flux as well.

    There's a handful of 2.2uF capacitors, around six in total, that haven't been replaced since that component order was lost in transit. The 330uF 400v mains filter capacitor hasn't been replaced since it was rather difficult to source, expensive and the existing one tested fine.

    One of the convergence strips around the CRT neck is still loose. While I've temporarily affixed it to the CRT with duct tape, I'll need to use a hi-temp sealant to permanently re-attach it.


    The CRT is bright, sharp and flicker-free in operation, even from a cold startup. The HDD seems to take a couple of attempts to start up still when cold, likely the result of a deteriorated rubber stopper, so I'll need to repair that soon as well.





    Here's an overview of the capacitors that were replaced (green labelled caps were replaced, red labelled caps weren't replaced but passed functional tests). You may wish to open this one in a new tab to see the image at its full resolution.




    Performance wise it's still extremely slow and due for a clean OS install. MJ313 over on ThinkClassic has also graciously provided a Macintosh LC 550 Logic Board to this build, so this Colour Classic will soon be powered by a Motorola 68030 running at 33MHz, with a faster system bus and a new memory ceiling of 36MB, raised from the 10MB that the standard Logic Board provides.


  13. #13

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    Fascinating post there - I'm so happy an Australian has gotten on board the re-capping challenge. You'll find yourself making some hopefully welcome cash on the side should you choose to accept delivery of boards for recapping.
    Jeremy

  14. #14

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    I've considered it and could probably manage it, just not sure how fast my turnaround would be.

    There's certain challenges with recapping boards as well. This Colour Classic fought back with burned traces and lifted pads, often without any force. (Literally the solder is the only thing holding them down, once the component is desoldered they lift.) This was harder on the Logic Board, since there were a couple of occasions where the pad disintegrated and I had to run some jumper wire to reconnect the cap to the board.

    I'd hate to have to tell someone that something awful happened to their board, but because of the age and condition of a lot of these machines, I can't guarantee that won't be the case.


    For what it's worth, even after a recap this machine still has CRT issues, including variations in brightness or intensity, flicker and sometimes deformation of the raster (the top corners will bow out even after adjustment, for example). I'm not sure what else to look into except perhaps dry solder joints.

  15. #15

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    I know that it's too late for you Michael but I am posting images for posterity's sake.



    I am editing this message because the image doesn't show inline, this is the URL: https://www.dropbox.com/s/xfgn5kclny..._9644.JPG?dl=0
    Last edited by Alex_Santos; 20th March 2017 at 09:11 AM. Reason: Image doesn't display

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