Macintosh Classic II Thin Line across Screen.

Discussion in 'Apple Collectors' started by Mars478, Jun 20, 2009.

  1. Mars478 macrumors 6502a

    Mars478

    Joined:
    Mar 6, 2008
    Location:
    NYC, NY
    #1
    I recently bought a Mac Classic 2 for 33$ on eBay knowing it was broken. It Supposedly has a broken "Vertical Sweep Circuit" I Turn it on and a Line appears on the CRT and no Bong or anything. Does anyone know of this problem?
     
  2. MacTech68, Jun 20, 2009
    Last edited: Jan 30, 2011

    MacTech68 macrumors 68000

    MacTech68

    Joined:
    Mar 16, 2008
    Location:
    Australia, Perth
    #2
    Unless you possess soldering skills and a long handled Torx T-15 screwdriver you'll be in for some bother. If you've taken classic/compact Macs apart before, you should be fine. Since you say the line is "across" the screen, I'll assume that you mean a horizontal line.

    Of course as always, there are lethal voltages running around inside and these machines and to do anything I suggest, you do so at your own risk.

    I'd suggest looking for dry solder joints on the Yoke Connector. A large 4 pin connector on the top forward edge of the Analog Board. If not, Try checking the solder joints where the bunch of mulitcoloured cables solder to the Analog Board itself. These are the ones around the speaker here. Of interest are the two wires that come from pins 4 & 5 of the motherboard 14Pin white Power/Video connector. See page 18 of the Developer Technote.

    You might want to make sure the Vertical Size adjust isn't faulty or broken (second adjustment from top rear of Analog Board).

    If you're certain the fault isn't the video from the Classic's motherboard itself, then other than checking for the usual suspects (cracked solder joints, bad capacitors etc) then there should be a vertical IC (possibly a TDA1170, but I can't find my notes these days). The VertIC should be the 14pin device next to the words "Bar Code Label" in the above photo left edge.

    If all that sounds like an alien language, try getting help from somebody familiar with the above description.

    There are a few sites devoted to SE30 and Plus Analog Boards, but none that I can find with specific Classic/II pictures and information (albeit after a quick search). The chassis are quite different so locations of components is not the same.

    One way to see if it's a cracked solder joint is to tap the Analog board with an INSULATED object and see if the screen momentarily (or semi-permanently) springs back to full screen. You can often do this without taking the back off. Just give the left hand top side a thump - enough force to just jar it.

    BTW, be kind to yourself if you haven't already and Google search the exact text below:

    classic_ii.performa_200

    Enjoy.
    ________
    Matador
     
  3. Mars478 thread starter macrumors 6502a

    Mars478

    Joined:
    Mar 6, 2008
    Location:
    NYC, NY
    #3
    Hey Thanks!
    You have been the most help I've found so far.
    I have worked on Compacts before but other people owned them. I finally bought my own!
    The Logic board seems to have some corrosion at the Caps at C14 and C6.
    There is no residue but some green stuff. I've posted a Picture of the Classic 2 here: http://www.flickr.com/photos/mars478/3643572749/
    (Sorry for bad Quality, its the iPhone)
    Is there any visual way to check for a bad solder joint?
    I Tried adjusting all of the controls you mentioned but only the top black one did something, it adjusted the brightness.
    On a side note, there is no startup bong.
    I want to get to the Analog board but Do I have to discharge the CRT?
    Thanks so Much!
    [EDIT] I did what you suggested by tapping the top of the Case, and now I have no video... hmmm Could this indicate a bad solder joint?
     
  4. MacTech68, Jun 21, 2009
    Last edited: Jan 30, 2011

    MacTech68 macrumors 68000

    MacTech68

    Joined:
    Mar 16, 2008
    Location:
    Australia, Perth
    #4
    Ok, this depends on how bad those capacitors on the logic board are. I don't recall which (if any) could cause a loss of vertical deflection.

    If they're too far gone, then the following won't work. Try leaving the machine on for about 20 minutes, to warm up those caps. Alternatively, use a hair-dryer for a MILD warmth and then quickly retest the board. When those caps start to go, warming them up makes them work again. Eventually, they'll leak and etch the tracks on the motherboard. If they haven't leaked yet, I'd suggest replacing them with Tantalum surface mount capacitors of the same value. Can be a bit tedious and very delicate work to get the old ones off without lifting/damaging tracks but it's well worth it since Tantalum caps NEVER leak.

    If you googled that phrase I posted, you should have detailed info in a pdf on how to dis-assemble your Classic II, including CRT discharge, which yes, I would always recommend if removing the Analog Board.

    Oh, BTW, to run the machine with no vertical deflection (that bright horizontal line) for a period of time may leave a horizontal burn mark on the screen. If possible, use the "Sub-brightness" or "Screen" adjustment to turn down the brightness if you need to run the machine. Just remember to not adjust the "Screen" brightness too high when it's finally working or mark it's position BEFORE adjusting it.

    Hmmm, maybe the CRT neck board is loose on the CRT and it's fallen off or there could be a dry joint on the CRT neck board and that's why you now get no video at all. Hard to say. I did say a gentle jarring, didn't I ? :eek:
    ________
    Mercury Marauder history
     
  5. Mars478 thread starter macrumors 6502a

    Mars478

    Joined:
    Mar 6, 2008
    Location:
    NYC, NY
    #5
    Hi there. The CRT Neck board is there and It is working... I see a little orange light in the glass part.
    I'll try leaving the machine on to see if the caps warm up and the solder joints as well.
     

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