Resolved I have decided to hack eMac's CRT (To work with any standard motherboard)

Discussion in 'PowerPC Macs' started by patriciooholegu, Jul 13, 2014.

  1. patriciooholegu, Jul 13, 2014
    Last edited: Sep 12, 2014

    patriciooholegu macrumors member

    May 18, 2014
    Oh, yes.

    (UPdate) Look at this:


    Pretencious as it sound.
    I decided this about a ear ago (midle of 2013).
    it was wen i saw this wonderfull machine for the first time in my life.
    I never knew about it till then, so i was shocked for the beautiful design on this thing.

    So...a few weeks back i bought one (1.42ghz, 2gb ram, bluetooth and airport from obb, nearly new from a cosmetic and functional view....)

    I'm a laptop - electronic level - technician.
    I already can confirm that a mini-itx + PSU + Heatsink and fan + 2.5" SSD will easily fit were the eMac logic board was before (Removing also the DVD drive).
    Not shure about enough room for ATX PSU but i have some idea about a stand were the emac body will be sitting on, and there will the PSU be.
    But actually all of this dont matter at all, since i have to do something huge first:

    Hack the eMac's CRT.
    Im planning on starting to make a few test in the upcoming days, and of course the key here will be the IVAD TO LOGIC BOARD CABLE, responsable for carrying vga and i2c signals to the monitor.

    Every inside on this will be usefull to my, but maybe, maybe someone has a better undestanding of the eMac's guts to know if this mean POWER ON and what is needed to make it work (Maybe even Leo Bodnar himself read this and have the answer to my question).
    Sorry about my nasty English...
    Thank for reading and stay close to see updates in the future.
  2. patriciooholegu, Jul 13, 2014
    Last edited: Sep 29, 2014

    patriciooholegu thread starter macrumors member

    May 18, 2014
    First attempt: Unsuccessful, but curious...

    I did my very first attempt today.
    By unplugging the vga eMac cable from logic board, you should recieve only a slight attempt of start from eMac logicboard: The machine himself and CRT are connected together and needed for a usefull behave.
    The eMac logic board can work without the CRT (But a complex trick like in this page is needed:
    The CRT WILL NOT WORK without the logic board...
    So i made a custom vga cable carring signals from a standard pc (Windows 8, Geforce graphics), but keeping certain signals on the emac to make shure that CRT start up.
    Like this:


    So therefore the necesary signals to start emac logicboad and crt was there, but VGA signals and DDC came from test pc.

    The result was:
    *The emac logicboard will start up but without any image on CRT (Of course).
    *Emac's CRT turn on but NO IMAGE apears
    *The testing pc DETECTS the eMac CRT as "Standard non plug-and-play VGA monitor" (Meaning: dont realize what the hell you just pluged in...) and will show available resolutions (Not matching eMac standard resolutions), and no picture apears, not even blank.
    *Manipulating resolutions on testing pc's GeForce Panel, even "Custom resolutions"...will not show anytingh on eMac's CRT.

    I must admit that this was a very early, dirty attempt. Mostly because the Custom VGA cable was made "On the fly" and not with propper VGA insulation standards, for example, and not very good soldering points on it, and myself feeling a little nervious with the project...
    Next point will be making exactly the same, but using good quality VGA cables...
  3. jbarley macrumors 68040


    Jul 1, 2006
    Vancouver Island
    why not go whole-hog with a flat screen such as this?
  4. patriciooholegu, Jul 13, 2014
    Last edited: Jul 15, 2014

    patriciooholegu thread starter macrumors member

    May 18, 2014
    *Because that's something already done.
    *Because you just need a lcd screen
    *Because eMac CRTs rocks!!

    I'm testing things right now on my partially disassembled eMac.
    Any help will be nice.
    Kind of suprissed that aparently no one as tried to hack eMac's CRT before.
    Tanks for answering!!
  5. jrsx macrumors 65816


    Nov 2, 2013
    Tacoma, Washington
    Are you planning to put a hackintosh into the eMac to work with the CRT?
  6. patriciooholegu thread starter macrumors member

    May 18, 2014
    It is not the main objetive.
    First i want to see a modern mainboard, capable of modern regular thing suchs as full hd flash video playing.
    But all depends on hacking the CRT.
  7. repentix macrumors regular

    May 26, 2013
    I was thinking of doing this to an original Macintosh, putting an ipad retina display in the case together with an itx mobo, sfx psu and ssd. The display would run off a converter plugged into the mobo. My problem with this mod is the price: 60 for the case, 100 for the converter, 60 for the display plus the cost of the other parts, it would be about 500€, too much for me.

    As to your project, I really like it!
  8. patriciooholegu thread starter macrumors member

    May 18, 2014
    That seems to be expensive.
    About the eMac CRT one even cross with the idea?? (Well, there are 2-3 post in google, but not real attempts)
    Thanks for your insides.
  9. 666sheep macrumors 68040


    Dec 7, 2009
    Look for Arkious posts about putting a hack in iMac G3 using its original CRT. You should get some ideas. Ofc it isn't an eMac, but some general rules apply to your case as well.
  10. patriciooholegu, Jul 14, 2014
    Last edited: Jul 15, 2014

    patriciooholegu thread starter macrumors member

    May 18, 2014
    That should be an insteresting reading, but the problem is i can´t find the particular page of the thread were they are talking about CRT hacking.
    Can you point my to there?
    Thanks in advance.
  11. patriciooholegu, Jul 15, 2014
    Last edited: Jul 16, 2014

    patriciooholegu thread starter macrumors member

    May 18, 2014
    Making progress...not!

    So after a few test i have come to the conclution that there are 2 fundamental pins going between eMac logicboard and IVAD board on CRT, involved on powerup process.
    In the wonderfull Leo Bodnar's page over here:

    is alot of information i readed over and over for undestanding how to make my project successful.

    This picture shows the pinout from logicboard to ivad cable:

    and i have decided that pins 10 and 4 goes high (+5v) wen the system start to run after power switch button is presed.
    If any of those are removed and power switch pushed, the system WILL NOT DO NOTINGH.
    So...i aded 2 standard 5v leds to those bad boys to see if there is any protocol betwen them, any on-of pattern and...system start-up normally but goes down!!; After changing the 2 standard size leds for others smaller, of less power consumption the system goes up and run as normal (This suggest that amperaje going here is really low and the first 2 leds are consuming all of it...TTL signals?).
    At first sight, the leds are always ON (Always high), but by recording the scenario with a webcam, a very slight activity is noted on pin 4 led: Don't know to tell if it is a protocol being happening, or just some effect of ambient light on the webcam, or variations of 5v signal due to the very small amount of electricity on that pin.
    Actually, wen the system was sended to sleep, and turned on again, the CRT didnt startup, but did the logicboard: I have to remove the 4 pin led...and CRT came back to service.
    Here is the video:

    After a few test I WAS NOT able to tell if those signals come from IVAD to Logicboard or viceversa (This is an important detail; i have to know from were those signals come).
    I'm tempted to make a custom vga cable using pin 9 from testing PC (pin 9 of vga computer offers +5v) pointing to one, or the other, or both IVAD pins. I should remove entire logic board and work with only the CRT (Actually this was the main idea for the project...By leaving things assembled i may mess things up and destroy the eMac's logic board).
    Also, by making this cable and feed those pins from elsewear, without knowing exactly what to expect, i'm at the risk of destroing the CRT...or even the testing pc.
    But dont think i will give up easy on this!!
    I have to make some other test on my lovely machine and i will report back.
  12. patriciooholegu thread starter macrumors member

    May 18, 2014
    Just found this usefull info on this same site:

    "Originally Posted by lbodnar
    On Gen2 board it works that way...

    Everything is warmed up by trickle 5V and standby 12V.
    Power On button push sensed by PMU controller on logic board.
    It sends message to a microcontroller on IVAD board (silver can) via two I2C wires on video connector. They are not VGA DDE data link and also used to control CRT brightness, geometry, etc.
    IVAD microcontroller sends PWRON signal (high) to analog board.
    Analog board inverts it and makes sure overvoltage signal (PRO) is OK (low)
    Inverted (low) power on signal (DPO) is sent to logic board via blindmate connector.
    It gets directly to downconverter and activates it.
    the rest of the magic happens

    As you can see it involves everything in simply powering the thing on!
    My solution is to just permanently ground DPO on the blindmate connector.

    Same logic and signals apply to Gen1 board too"

    Anyone can tell my the code of this Ic on IVAD board (Silver can), so i´m able to look for schematic on google?
  13. MrDandyMan macrumors newbie

    Jul 24, 2014
    There's an old eMac I might be able to get my hands on that is in good working order. If this hack works, I might borrow your idea to turn it and a raspberry pi into a classic game machine.

    Keep up the good work!
  14. apple apple macrumors member

    Jul 22, 2014
    I love the idea.

    I have done the switch in an emac to lcd, then crammed an intel mobo in there, but I must admit your idea of reusing the crt monitor is way cooler.
  15. patriciooholegu thread starter macrumors member

    May 18, 2014
    Back from vacations, ready to work hard

    So no updates as come in the past few days.
    I was on vacations, travelling, and now im back for this project.
    Will remove eMac's logicboard tomorow and maybe disassembly IVAD board to trace things up, and reverse engineering.
    I Will come up with updates...
  16. patriciooholegu, Aug 21, 2014
    Last edited: Aug 22, 2014

    patriciooholegu thread starter macrumors member

    May 18, 2014
    Good news

    So updating:
    I just figured out how to turn the entire crt (Tube, Ivad, analog board) without need of the logicboard: You have to feed +5v to pin here (Of course, also ground. The pink one on the side, for example):

    The curious thing about it, is that signal goes to IVAD board, but passes trough it (And a bunch of resistors in the meantime) and finish on analog board to pin "PWRON" :

    So, explain to me the trouble of eMac's designers on making the dam thing go to Ivad, just to pass by to another board, and not directly to it?
    As long as there is 5v you will going to have the CRT turned on!

    Of course, no picture comes up from the CRT at the time being (I'm looking to thest a few "Custom resolutions" based on the data here: and wait to have good luck)

    Therefore, to power up things, the chances are, as i see it:

    1: Provide +5v using pin 9 from testing pc (Pin 9 from any modern vga port should provide low amp 5v, but i have noticed that alot of vga cables, mostly cheaper ones, don't have that feature; Not a problem for my, since i have an "old school" one, good quality, were the manufacturing cost and profits was less important than the customer happiness, ready to be modified to my needs).
    In this way, eMac's CRT should be responsive-slave to motherboard orders, in terms of turning on-off, going into sleep, and other things.
    2: Other way should be to turn CRT by a switch to let pass Trickle voltage from eMac's analog board. Notice pin 14 in this picture:

    Here should be another switch, to turn motherboard, and therefore you will end up with 2 switches to push: CRT switch and motherboard switch (Like your standard desk computer: case button and monitor button). In this scenario you may turn-off CRT, meanwille motherboard stay working.

    This are 2 ways of handling the situation: my particular choice will be to manage all of it with the eMac's original power button (Just like original eMac was), so option 1 is the way to go.

    Please, please, sorry about my English!!
  17. 128keaton macrumors 68020


    Jan 13, 2013
    Awesome! Sounds like its about ready for a proper adaptor cable and a ITX motherboard
  18. apple apple macrumors member

    Jul 22, 2014
    Oh man, could you imagine an i3 intel nuc powered emac with a real crt! That would be awesome.
  19. patriciooholegu thread starter macrumors member

    May 18, 2014
    Actally im looking right now at my lovely eMac and im prety certain that a mini-itx mobo will fit well in there (With 2.5 ssd + laptop form factor dvd reader, and maybe a low profile video card, or a tv tunner card...). The trouble will be to put an ATX Psu, but trouble, not imposible.
    Don't like much does "Nuc" craps. Maybe you do, don't be mad.


    i'm about to finish a lovely (Kind of "A la Mac" sort of quality) cable for that.
    Maybe this weekend should be the miracle?
  20. patriciooholegu, Sep 10, 2014
    Last edited: Sep 12, 2014

    patriciooholegu thread starter macrumors member

    May 18, 2014
    Oh my god: The eMac CRT as being hacked!!!

    Look at this picture...


    It happened about five minutes ago...
    I have my hand shacking, man.
    It gives me chills right now.
    This may be an entire change in the eMac's history and destiny (Being able to replace that 10 years old logicboard with any actuall mini-itx mobo?)
  21. apple apple macrumors member

    Jul 22, 2014
    Nicely done sir! Now you just need to get windoze off there. I understand why you would favor something like a gigabyte itx over a nuc... but maybe the nuc would allow for a full size dvd drive in there. I know it is not important to most, but after all that hard work to keep the crt wouldn't it be nice to maintain the illusion of stock?
  22. patriciooholegu, Sep 13, 2014
    Last edited: Sep 13, 2014

    patriciooholegu thread starter macrumors member

    May 18, 2014
    Thanks for the kind words
    I´m in the same line as you about keeping all stock...That´s the reason of hacking the eMac CRT!!
    Im planning to make a nice Yosemite hackintosh with it (I have to read more about VGA drop since Mac Os 10.8, i think i´m busted and forced to Mac os 10.7).
    The reason to dismiss Nuc is that they are quite expensives in my country.
    And also like the idea of PCI-Express video board (I already have a Ati HD5570, aparently works on hackintosh)
    Dont think that a mini-itx mobo will fill the place of a dvd drive. Maybe it fits (Maybe i´m too positive).
    Uptading: lastnight i found the way to turn and feed the CRT completely from the standard PC, dismissing the eMac logicboard.
    I will make a fully explained "How to" in the upcoming weeks.
    And i see even more straightforward to hack the iMac G3 (I have one...)
  23. LightBulbFun macrumors 68000


    Nov 17, 2013
    London UK
    Yosimite/Mavricks and VGA

    hey I Noticed your concern about running 10.9/10 with the eMacs CRT due to it being a VGA display well I can tell you now that with a Geforce 210 the VGA out works wonderfully in my Mavericks and Yosemite hackintosh my only monitor is a crappy VGA LCD one I have since upgraded to a EVGA Geforce GT 740 and with a DVI-VGA adapter its still working lovely My display is a HP w19ev if that helps. I think HD 3000+ graphics lost VGA seport but thats it
  24. patriciooholegu thread starter macrumors member

    May 18, 2014
    Logic analizer needed

    So it seems to be that Sda-Scl signals coming from (or-to) eMac logicboard are a must in powering up stage to see a proper image on the CRT.

    After a few second you may unplug those, and the CRT will run just fine.
    Tracing down to were they go, in logicboard straig to the ATI vga chipset, and in IVAD board to i2c traces (All i2c devices share te same wire, thats the fun of it) were 3 IC are.
    Replacing the logic board with i2c signals coming from testing pc dont provide good results: Dont know whats going on in there, but without those the CRT hack shows a pretty distorted, ogly image (Like if something in the IVAD board didnt turn on).
    So im in the process of building a simple home made Printer port based, Logic Analizer like this (I do not have a commercial one) :

    The idea is to bridge pins betwen logicboard and CRT to this device plugged to a windows xp, or maybe the good old windows 98, since in there the interaction with LPT port runs without protocols.
    Also found this (Simple wire-to-wire connection without any protection, may damage something):
    Anyone have done this? (Bridge i2c to parallel port without any protection betwen?) mostly i ask because i dont know if i will find the needed IC 74HC245.
    I dont have concerns about mess the xp machine (It is a old pentium 3, i have 5...) but more about my lovely eMac...

    Attached Files:

  25. Goldenbird, Oct 28, 2014
    Last edited: Oct 28, 2014

    Goldenbird macrumors newbie

    Oct 28, 2014
    patriciooholegu - Are you still there?

    It's been a month now, have you given up? If so why. ?

    ....goldie :(

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