I opened the neck back up and wrapped the ethernet wire with some aluminum tape. I tried to get it down into the super skinny part but the angles were too extreme. All in all, I probably covered 95% of it, but that either wasn't enough or wasn't the problem because the display still had the same issues.
I need to track down some ferrite cores and try those, though I fear even if they do solve the problem, the one that will need to go behind the display won't fit. We'll see I suppose.
I'm still in the process of trying to track down somebody who actually knows about this sort of stuff. There's an uncle of a friend who might, and I'm also working to track down some electrical engineering professors... we'll see.
You should contact this guy and find out how he did it. He was able to wire video through the neck and connect it to a mini itx motherboard in the base of a 17" imac g4. The pictures on his blog are excellent and may be of benefit you.
ReplyDeletehtp://blugray.tistory.com/
Yeah, I think somebody posted this tip earlier. It was very interesting to see. The blog is all in Korean and the google translation of it was incredibly different to understand but I was able to figure out how he did it.
ReplyDeleteHe used the original display from the iMac and found (somewhere) what he called an "AD board" which I think is the same as the "TMDS controller" they've been talking about on the MacRumors forum. (link below)
I did not go this rout. It seems like it might be an easier way to go but when I was doing my original research, I never found a place to buy one that didn't feel super sketchy. Having no experience with these sorts of things, I opted to replace the monitor.
http://forums.macrumors.com/showthread.php?t=224698&page=7
I hope you are going to continue with this project (and blog of course)?
ReplyDeleteI commented on your first entry a while back, and I still want to do something similar, but with a mini-itx board and pico-psu.
Got all the 20" iMac parts I need, including a complete empty shell with drive cage, spare necks and NOS (new old stock) screen frame and bezel.
Also a working one with non-working monitor (VGA out works ok), and a couple broken 15" I can cannibalize for parts and practise on.
Now I just need an ION mobo and RAM and PSU, but funds are now short. Going with the 20" also added cost as they go for almost double 17" prices on eBay.
I have a couple of Dell 2007WFP 20" monitors although buying just an LCD panel might save butchering a good monitor.
I think it's the same S-IPS type LG LM201W01 panel that the iMac uses, as I checked the serial #, AND it passes HDCP unlike the 2005WFP with the same panel.
Was hoping to use existing neck wires to send a DVI signal up the neck, but then there's the issue of the power supply, and maybe not enough wires?
I am indeed planning on finishing this project and blog all the way though. I even have some other projects I've been lining up to do after this one's complete. School has been hectic, but I'm looking forward to doing some more work on this soon.
ReplyDeleteIt sounds to me like you're pretty well set up and ready to go. Remember you can't feed a DVI signal directly into the LCD panel. You need the video board that comes in the LCD monitor, and that won't fit behind the LCD screen in the top. Both the power supply and that video board need to be in the dome unless you want to modify the back of the iMac's LCD housing like jberg44 did in post 144 of the below linked blog.
You should be able to use the wires in the neck though. It's just a lot of difficult soldering.
http://forums.macrumors.com/showthread.php?t=224698&page=7
Dave, I was finally able to get video wired through the neck of the 20 inch iMac. I had to replace all the wires in the neck. I used 30 gauge kynar wire and older lvds cables. I suspect some of your difficulties may be due to problems with using the existing wires in the neck. Hope this helps. I have more info on my blog. - Jon
ReplyDeletehttp://dremmeljunkie.blogspot.com/
Yeah, I'm thinking I'm going to have to do this. Thanks for the tip on the Kynar wire! I've been tinkering a little with it over the last 2 months and nothing seems to be working.
ReplyDeleteHey Dave, I'm glad to see your still working on this. I am pretty sure I have realized exactly what is causing your interference. My signal started going crazy with the backlights turning on and off similar to what you've described and then fixed the problem with the addition of a proper inverter extension cable.
ReplyDeleteThe pink wires (I believe there are two backlights in the 17" version) that connect the inverter to the backlights carry a high voltage signal. The white wires carry a low voltage signal. If you are running these through the existing wires in the neck you are probably running into one of two problems
1) The gauge of wire in the neck is too small and not properly shielded so the backlights are shorting out. The name of backlight wire is UL3239-3KV wire. You can search for that or just look for backlight extension cable. CAT5 can carry the voltage, but really scares me. During testing I saw the electricity arc - an actual blue spark to a nearby wire - from one of the poorly protected solder joints. After that I decided to use only properly shielded high voltage wire for lengthening the inverter. You are running it through a metal neck. (Remember you only need it for the high voltage/pink side, so its only two wires).
2) Because you have a poorly shielded wire carrying a very high voltage signal in a group of wires which are carrying your LVDS signal I can guarantee this is causing interference. I was able to visibly demonstrate this. When I moved a CAT5 wire carrying the high voltage inverter power near the unshielded LVDS wires, the image started flickering and eventually was lost entirely. When I shielded the LVDS wires by griping them in my hand the signal returned.
So again, I no longer think you have to rewire everything, but I think you have to separate the two high voltage inverter cables from the other LVDS wires and I would strongly advise using some type of high voltage wire for safety.
Sorry for the long post, but I'd certainly love to see your finished mod and I hope this solves your problem. Please let me know if this works. Thanks, Jon (jberg44)
Haha Please, post as much as you'd like. But this information is extremely helpful. I looked around a little online and didn't see anybody carrying those High voltage cables. Do you know where I could get any?
ReplyDeletewww.quadrangleproducts.com has all these sorts of wires and cables. But you usually have to buy unnecessarily large amounts.
ReplyDeleteAlternatively you can just look for backlight of inverter extender cables on ebay. they are commonly used in certain laptop models. I got some for a couple dollars on ebay. They originally belonged to HP Omnibooks, they are 15" long so it does take 2 to make it through the neck.
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