Sunday, September 20, 2015

Junk 2006 iMac repair - Part 2

Continued from Part 1.

I checked around for a replacement display and ended up buying a Samsung LTN170X2-L02 (datasheet) for $25 shipped. Bargain.

Another thing the UniMac adapter comes with is a "Y cable" for the inverter since the original screen has 2 CCFL lamps while most 17" laptop displays have 1. This cable simply connects the two outputs together and the combined output to a single lamp.
I'd recommend NOT trying this with any other inverters without checking datasheets and schematics unless you're trying to fry something. It's safe with the particular inverter model used in the iMacs, NOT all inverters universally.

I had several CCFL extender cables left over from a previous buy so I used two of those to make the adapter.


So then the display arrived like this:


No apparent damage though, so I hooked it all up.

It ain't pretty but it'll do

Moment of truth!

I'll be damned. First try even. Complete with perfect example of why I hate glossy screens.

Not getting any output from the firmware was a bit alarming but it does start working after a few seconds of blackness. Never ended up messing with the EDID. I'm fine with no Apple logo or boot menu on this machine since it's only ever going to run one operating system (which coincidentally isn't even Apple's) anyway.

So now came the most annoying and time-consuming part of this whole project, if you can believe that: Mounting the display.

I wanted to use the original brackets but the holes were all in the wrong place. Not only that but the right side bracket has gaps where the new display had screw holes.. Ugh..
This is starting to sound like an ad but note that the UniMac also comes with universal brackets so for $25 it's not a bad deal considering how much trouble it saves you from... Since I'm a cheapskate though, ghetto measures it is!

Yeah.. It's not pretty. The right bracket was even more of a pain as I had to add plastic L-brackets to fill the gaps in the metal.

If memory serves you need to shim the display around 6-8mms from the left side if you're using the original brackets as a base. I did 5-6 (the nut in the picture above) and it's just ever so slightly not enough. Annoying.

Especially since it's not so bad here:

But once everything was snapped back together it moved a little bit to the left. !@#!

I already added some epoxy to keep stuff from moving so I just left it as-is. It isn't something you really notice unless you know what to look for and I actually couldn't see it when I looked at it a week later.

In hindsight I probably could've just used contact glue or double-sided foam tape to glue the display directly onto the front bezel since it weighs almost nothing. Oh well..

Total cost $55 and a few hours of my time.

Not bad for a compact Core2Duo system that's still more than adequate for email and light browsing.

Still going strong in 2017. I just (4th of February) took it apart to redo the thermal paste on everything as the Radeon was idling at 71C even with the 80% underclock I had on it since day 1. I really want this to last so it had to be done since if it's 71C now It no doubt would've burst into flame under any sort of load at full clock. 
I might eventually have to buy a mobo from an integrated graphics model when (probably not if) this finally gives up the ghost. Applying some expensive "overclocker's" grease I had left from the old days helped somewhat (5-10 degC lower), I hope that buys it another few years at least.


Still going strong in 2018. I just replaced the Samsung display as the soldering of the CCFL tube failed which led to arcing which made the display's controller chip go into a reset loop or something. First time I've seen that happen. You'd think the display is completely dead and it's just the lamp arcing that's making it do that. I was feeling lazy so I very destructively removed the failed lamp and duct-taped one from the original broken LG display in it's place which worked fine as a temporary fix until I got a new one. (They're even cheaper now than when I did this project so I didn't feel like doing an LED conversion on the Samsung) Bought an AUO display instead for $20 shipped. The Samsung had better colors (IMO) but I've never had any issues with AUOs and color reproduction is not important for this machine so.. here's to hoping it lasts like the others I('ve) own(ed).
2020: CPU overheating issues. Turned out that the heatpipes in the CPU heatsink have failed. I would not have believed it if someone had told me this happened to them. I removed all the heatsink fins to confirm and neither of the heatpipes were conducting heat at all. A donor machine was purchased and the heatsink and newer looking(less browning from heat) PSU were swapped in. 
The "New" PSU promptly died 2 weeks later, old PSU swapped back in.
2021: Old PSU died. We're done with internal PSUs now, it's external PSU bodge time.

Old mac on life support
The DIN-rail thing I had lying around can do 12V/8A while the original PSU did 15.4A. I think I did some measurements with 100% CPU at some point and it should be fine but I figure the industrial thing should have good overload protection anyway. 
In the future if a working machine can't be created using remaining donor parts and stuff from my hoard then they're both going to e-waste and my father will get my old IdeaCentre which still works fine (it's original PSU also died several years ago but it was much easier to deal with since it was external from the beginning and it's 19V so it runs off any old 90W laptop charger just fine).

Saturday, September 19, 2015

Junk 2006 iMac repair - Part 1

So my father's browsing PC bit the dust. It was a 15 year old dinosaur with USB1.1, SD-RAM and a Northwood core Pentium 4. Wasted way more time trying to save it than the whole thing is worth. PSU troubles first then nothing working out right with the new (read: only 13 year old) PSU either.
Crappy Molex connectors, ancient barely functioning HDDs, etc. I gave up at the point where it became clear that money would have to be spent in order to get the thing running again. Simply not worth it.

So I went online and bought a BRAND SPANKING NEW ...

Just kidding, I bought this:

A Late-2006 model iMac A1208 (2Ghz Core2Duo, 1gig of ram, 160gig hdd)  for $30 shipped, not a terrible deal.

I was pretty confident that I could fix it up on the cheap based on some initial research.

As you can see the screen is broken but that didn't bother me since most (all?) of these were sold with defective LG displays that developed vertical lines after a few years of operation anyway.

Now you'd think you could just install another 17" panel but of course it's never that easy.

The display Apple used in the machine has a "weird" pinout. I'm not sure if there's really a standard or if it's just some manufacturers agreeing to a certain pinout a few years after this machine was released but the majority of compatible displays will have a pinout that's different from the iMac's.

Since most of these machines developed vertical lines and most readily available displays couldn't be used with them an opportunity presented itself for anyone willing and able to design an adapter and so the UniMac was born.

The thing is a pin-swap board that lets people use the original LVDS cable with the new "standard" pinout displays. It also includes an 24C02 I2C eeprom that spoofs an original display's EDID for the firmware (you didn't think Apple would just let you swap parts out like that did you?)

In addition the onboard eeprom also enables using newer displays that don't come with an EDID eeprom at all.

That said...

IF your replacement display has an EDID eeprom then (even though the firmware will reject it) it will work once the machine is booted.. at least with the discrete graphics model.
What this means is you won't get the Apple logo or any other output from the firmware (boot menu, firmware upgrade screen, etc..) but it will work fine within OSX as well as Bootcamp, even in text mode.

If the Intel graphics model doesn't want to work this way or your display doesn't have EDID at all (or you're just really keen on getting video output from the firmware) then you need to get a 24C02 (24C01 might work too) eeprom loaded up with the original display's EDID data and hook that up to the appropriate pins.

The EDID data from my broken display for reference:

Also, if you DO have EDID but want to be a perfectionist you could try to find the part the firmware looks for and merge only that with the original EDID data of your display. I'm not sure if it actually makes a difference or not.

Now luckily the original connector has all of the pins in it (ie. it's not the type where unused pins are missing) which makes it ideal for a DIY conversion. So that is what I attempted.

The metal casing is attached to the connector with a few tabs and some glue but you can tease it apart with tweezers.

There's hot glue at the base but it doesn't adhere to much. You can just push it down the wires.

This part it finicky and requires a lot of patience and several different tools. The center part slides out. 

Slowly and carefully..

I'm sure there's a production jig/machine for this connector that pushes it together. It's really not made to be disassembled again so just keep that in mind and treat it accordingly. It took me about 20 minutes to pull it apart.

Pin-swap time!


I did solder the missing grounds afterwards and just connected them to the exposed ground lead

The pinouts are as follows:

Left is the original LG display and right is the new "standard"
Credit goes to Jim, author of じむのとりあえずやってみたの巻 who has an 8 part series on doing the same thing with no prior knowledge (in Japanese).

All wires are color coded so I've made these additional notes while doing the conversion:

Thick green wires are ground
Orange wires are +3.3V (you'll have one left over after conversion)
Black is DDC Data
White is DDC Clock
Pink is DDC Vcc

LVDS pairs are individually shielded in colored cables (peel back the black cloth-tape further if you can't see them)
These outer cable are:

Green: Even 0
Blue:  Even 1
Magenta: Even 2
White: Even Clock
Black: Odd 0
Red: Odd 1
Brown: Odd 2
Yellow: Odd Clock

LVDS inner wires: Green is POSITIVE, Red is NEGATIVE

After all that I put the connector back together and added some tape.

A drop of mineral oil on the pins helped with reassembly.

Now I just needed a new screen.

Continued in Part 2.