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jguay
March 6th, 2012, 01:21 PM
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

jguay
March 6th, 2012, 04:14 PM
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.

http://i61.photobucket.com/albums/h75/jjguay/Mac%20SE%20FDHD/DSC04658-1.jpg
http://i61.photobucket.com/albums/h75/jjguay/Mac%20SE%20FDHD/DSC04659-1.jpg
http://i61.photobucket.com/albums/h75/jjguay/Mac%20SE%20FDHD/DSC04660-1.jpg
http://i61.photobucket.com/albums/h75/jjguay/Mac%20SE%20FDHD/DSC04661-1.jpg

jguay
March 7th, 2012, 12:41 PM
Anyone???

Al Kossow
March 7th, 2012, 12:47 PM
Anyone???

It will be easier to find a replacement tuning slug.
Have you tried both ends, and lubricating the slug?

jguay
March 7th, 2012, 04:38 PM
It will be easier to find a replacement tuning slug.
Have you tried both ends, and lubricating the slug?

Yes -> "Also tried a squirt of De-Oxit FaderLube - no dice.". It seems really stuck and will not rotate at all when I place any tool in it. This is the problem - it will not rotate in either direction AND the end is broken off or chipped off, making the tuning slug shorter than original (and possibly making it so it cannot be adjusted since the length of the slug is integral to it's ability to be tuned).

barythrin
March 8th, 2012, 11:21 AM
Dumb as it might seem, sometimes if a non-functional part which you have good access to is stripped you can use a small saw blade to create yourself another flat-head grip to try again. Is there a specific reference/document you've found so far that you're going off of? I posted one on the obsolete-computer forums although it was just a quick result in google which also had another location to look at for symptoms of screen resizing or fluctuating.

jguay
March 8th, 2012, 01:42 PM
Dumb as it might seem, sometimes if a non-functional part which you have good access to is stripped you can use a small saw blade to create yourself another flat-head grip to try again. Is there a specific reference/document you've found so far that you're going off of? I posted one on the obsolete-computer forums although it was just a quick result in google which also had another location to look at for symptoms of screen resizing or fluctuating.

I have the service manual and schematics - the schematics do not show the value of the inductor. I have a EE background so none of this a daunting to me (I used to restore vintage stereo receivers and re-sell them). I was just looking for some good, informed advice. It sounds like the specifics of the variable inductor are pretty forgiving, since the circuit is designed to be tuned anyways.

Chuck(G)
March 8th, 2012, 02:05 PM
The width coil and yoke are usually a matching set, so the value probably wasn't given explicitly by the manufacturer.

It looks as if it's wound with litz wire; most of the width coils in my junkbox are wound with solid wire. I suppose you could get a junker width coil and wind it yourself... Maybe some of the arcade folks would recognize what you have.

jguay
March 8th, 2012, 02:43 PM
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?

Chuck(G)
March 8th, 2012, 03:45 PM
Steal a slug from a junker CRT TV or monitor--they all have these coils and the slugs are pretty much interchangeable.

Or consult the arcade supply vendors who sell the whole width coil assembly (http://www.lizardlick.com/Electrohome-G07-Horizontal-Width-Coil_p_49.html). These fail all of the time.

I trust that you're using a non-metallic (usually nylon or delrin) tool to make adjustments "on the fly".