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Apple Mac SE Horizontal Adj Inductor (L2)

Discussion in 'Troubleshooting and Repair' started by jguay, Mar 6, 2012.

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  1. jguay

    jguay

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    Mar 6, 2012
    I have a Mac SE FDHD that has the screen a bit too wide. I opened it to adjust things and see the variable inductor (L2) is a bit messed up. The hollow core (that a non-conductive hex tool goes inside) has been chipped on the ends and I cannot rotate it to adjust it. I would replace the variable inductor with something new (Digikey or Mouser) but do not know the component values (uH, etc...).

    I found the schematics online for the SE, but still cannot find info on this inductor to find a suitable replacement.

    Does anyone have any info/guidance on this? Thanks, in advance.

    -- Jason
     
  2. jguay

    jguay

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    Mar 6, 2012
    Pics of the variable inductor

    Here are a few pics I took of it. The internal core is hollow and chipped off on the end. As I stated, I tried using a non-conductive hex tool to rotate it, but it won't budge. Also tried a squirt of De-Oxit FaderLube - no dice.

    The screen on the Mac SE is too wide (meaning, the mouse goes off the screen on both the left and right sides when booted). My thoughts were to replace the inductor. My problem is I cannot identify the specs of this inductor anywhere and don't know what a "suitable replacement" would be.

    Again, thanks in advance for any help.
     

    Attached Files:

  3. davenn

    davenn Moderator

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    Sep 5, 2009
    does the schematic now have any component values on it ?
    or does it just not have it for this inductor?

    Probably not something you would buy at digikey etc anyway
    more likely a specialist spare part from Apple

    As you have discovered, its really easy to crack ferrite cores. Sometimes, if you are really lucky you can access it from the other end of the former, either via a hole inthe PCB or unsoldering the coil and former.

    On rare occassions, when spare parts have not been available, I have had to be rather brutal and literally smash the old core into bits so it would fall out and then insert a new ferrite core.

    do you or a friend have an inductance meter to measure its value ?

    Dave
     
  4. jguay

    jguay

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    Mar 6, 2012
    @ davenn - No, I do not have access to an inductance meter. I have several multimeters and an oscilloscope, though. And, yes, I did try accessing it from both ends to rotate the core, but no go. Being a "physical" item, I thought maybe being old it would benefit from a bit of lubricant, but no dice - even today I tried again to turn the core with my tool but it won't budge. Since both ends of the movable core have been damaged (chipped off) I'm guessing it needs to be replaced.
     
  5. jguay

    jguay

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    Mar 6, 2012
    OK, so tonight I went ahead and cut away the outer plastic tube around the ferrite core and the core just basically crumbled. So the inductor has no core at all. I've read about using a substitute core (like a regular screw) so decided to go that route for an experiment.

    Once the crumbled ferrite core was removed I inserted a regular iron screw and powered it up - the display is still "too wide" so I went to adjust the screw and it was hot as hell so I powered off immediately. No harm done to my SE, but seems that inserting a solid metal screw will cause a fire hazard due to the heating up. The SE powers up fine and all, it's just I have no ability to adjust the horizontal width of the display, which is now maxed out on width (since there is NO ferrite core anymore in the variable inductor).

    Any suggestions on my next move?
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Get a new ferrite core.
     
  7. Neotron

    Neotron

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    Mar 9, 2012
    As Steve says, just get a new ferrite core, any electronics shop will have them, you might have to buy a coil with it.

    All you need is the length and diameter and the thread type (prob. metric). Eyeball it.

    By the way, your macro photography is good, how'd you do it?
     
  8. jguay

    jguay

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    Mar 6, 2012
    I have an older Sony point & shoot digital camera (nothing special) that has a Macro button. I simply push that button and can get within an inch or 2 of whatever I am taking a picture of. It just works.
     
  9. Neotron

    Neotron

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    Mar 9, 2012
    I struggle to do good quality macros and I've got three digitals, one of'em cost me $1500!

    Fixed your Mac yet? You could pull the plastic insert out, plug a new bit of ferrite that is about the same size in there and drop a little bit of wax into it when it is about in the right place. The little bit of wax will stop it from moving too much and make it easier to adjust to get the right position. When you've finally got the right spot then just fill it up with wax.

    If you've got any old analog TVs around then rip the chassis out and you'll find a few ferrite cores on the main board. Save them all, I do.

    I've got an old MAC SE that has stopped completely (might be the power supply) which I haven't looked at yet.

    Are there any circuits around that is free?
     
    Last edited: Mar 10, 2012
  10. jguay

    jguay

    6
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    Mar 6, 2012
    A member of another messageboard that I posted this issue to has offered to send me the part I need, so waiting so see if that pans out. I'll post again when I have news on my variable inductor issue.
     
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