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.

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 (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.

Tuesday, March 10, 2015

[Random Teardowns] VGA to composite converter box

Device: VGA to composite/s-video converter
Origin: eBay / China
Reason for teardown: Curiosity
Impressions: Feels cheap, looks cheap, is cheap, works well enough.

EM636165-TS7 (datasheet) DRAM

VX1937 (datasheet) one chip solution

Wednesday, November 26, 2014

[Random Teardowns] Hyundai 30GB USB microdrive

Device: Hyundai Digital 30GB USB microdrive
Origin: DX / China
Reason for teardown: Died
Impressions: Didn't mind the construction of this but it always took over 30 seconds to enumerate on USB. Maybe I should have sent it back immediately but well.. it did work. Until a few days ago.
This thing is essentially a 1" Samsung Spinpoint HU030HA 30GB ZIF/PATA microdrive and a usb interface board with an obscure Moai M110E interface chip.

The Moai chip appears shorted. Maybe I can buy a ZIF interface board to save the data off the drive at least as it still seems functional.