7600 monitor rejection

Discussion in 'Apple Collectors' started by HavingFun, May 22, 2011.

  1. HavingFun macrumors newbie

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    #1
    I'm clearing out junk, but the 7600 doesn't like the two CRT I wish to keep. Why would that be?

    7600/120 OS 8.6 64mb. I get no signal on the 17" IBM G78 and 19" Viewsonic PF790.

    But it works fine with a 17" NEC MultiSync70. Unfortunately that one is headed for the skip -- it overheats after a while, shuts down, then doesn't come back on for days. There was flyback flaw that plagued that particular model.

    I'm using a good quality Apple brand adaptor. The manual claims the default 2mb video ram will handle up to the Multiple Scan 20 at all resolutions, just with less colours than with 4mb.

    FWIW the NEC is a '99, while the others are '01 and '02.

    So I'm at the head-scratching stage now. Why would the 7600 be fussy about this?
     
  2. MacTech68 macrumors 68000

    MacTech68

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    #2
    According to this, the PF790 is capable of:

    1,600 x 1,200 @ 77Hz
    1,280 x 1,024 @ 90Hz
    1,024 x ,768 @ 118Hz
    ,800 x ,600 @ 149Hz


    The 7600 resolutions are
    512 x 384
    640 x 400
    800 x 600
    832 x 624
    1024 x 768
    1152 x 870
    1280 x 1024

    Unfortunately, the maximum refresh on the 7600 is 75Hz. See "Table 1" here.

    Snookered. Unless the ViewSonic or IBM can do 74-75Hz :(
     
  3. chrismacguy macrumors 68000

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    #3
    The G78 *should* be able to handle 1280*1024 out of that card... (IIRC 1280*1024 at 75Hz was one of the settings it took...)
     
  4. HavingFun thread starter macrumors newbie

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    #4
    I have to apologize for not being too bright here. The way I read it, those monitors can handle more than the 7600 can do, but isn't it the nature of a multi-sync CRT that those specs are maximums, and these CRTs should simply display the lower output that's within the 7600's range?

    Here's the NEC specs while we're at it.
    http://www.necdisplay.com/documents/UserManuals/ms5790f.pdf

    And yes, 1280*1024 at 75Hz is listed for the 7600 on the Apple Multiple Scan 20" (albiet at 256 colours), but only for that one. Lesser resolutions are listed for the 17" and smaller.

    I've never had these monitors hesitate to display very old PCs with weak cards, so please forgive my expression of blank stupidity right now. What am I missing?
     
  5. MacTech68 macrumors 68000

    MacTech68

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    #5
  6. HavingFun thread starter macrumors newbie

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    #6
    Not on that page. 513-0092-A

    Looks like the 590-0322-A, but is opposite gender. (and in clear plastic rather than grey)

    Found it in the earlier version of that page,
    http://web.archive.org/web/20080314184247/http://docs.info.apple.com/article.html?artnum=33001

    I've got a 590-0322-A here too. They're dimensionally identical, just a gender difference and a slight smoothing and simplification of the updated plastic wrap for the iMac era. But all markings are in the same places and proportions.

    Third item, one on the right.
    http://www.emc2cs.com/tech_tips/files/monitor_display_adapters.html
     
  7. MacTech68, May 23, 2011
    Last edited: May 23, 2011

    MacTech68 macrumors 68000

    MacTech68

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    #7
    I wonder if you should install Apple Displays Software 1.7.1

    http://download.info.apple.com/Appl...l/Apple_Displays/Apple_Displays_1.7.1.smi.bin

    The on-board video card may not be able to recognize the Sense Code of that adapter.

    Also remember that the sense code is ONLY queried at power on, so you MUST have the adapter connected when you initially power on the 7600. If you swap adapters, you MUST reboot for the sense code of the new adapter to be read.

    The 21" should support the scan rates listed here:

    http://support.apple.com/kb/SP139

    BUT, if the 7600 can only go as high as 75Hz, then the 85Hz VESA resolutions aren't available. Maybe that's where the Displays Software 1.7.1 comes in handy. It's too long ago, I don't remember. :confused:
     
  8. HavingFun thread starter macrumors newbie

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    #8
  9. MacTech68 macrumors 68000

    MacTech68

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    #9
    Later Mac models do support DDC on SVGA. VGA had a similar "analog" method but only defined 3 types of displays.

    It was a good idea to use simple logic (simple to implement physically too) to let the Mac know what model of monitor was connected and thus, the Mac knew (via a list in the OS) which resolutions could be used.

    I think the Blue&White G3 was the first to support DDC.
     
  10. HavingFun thread starter macrumors newbie

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    #10
    Back at it. Did some reading, and found some things.

    I don't have the backup software, so it's a poor risk. It's unsatisfying to leave a good suggestion untried, but there it is.

    Searching further found more mentions of the same trick, so I've just cobbed togther a male-female DB15 avec diode to stick between the Apple and the SVGA adaptor. I get this on the G78:

    640x480 67mhz
    852x624 75mhz
    1024x768 74mhz

    I also get that if I reverse the diode, or remove the diode. I get nothing if I remove the cobbed DB15. Also when I do get display, I get it in pink.

    This is a pastime, so I suppose I am delighted at the expanding mystery.

    The cobbed cable is made from a gameport and a cord ripped off a discarded Apple 17". It was discarded for going pink.

    I did test that cord to be assured that each wire was only connected to one pin. However I did not test thoroughly enough to notice if there was any diode inside.

    Guess I'll check that next. I would have thought Apple would put the Sense Code tricks inside the monitor rather than the cable, but in hindsight there is no reason to presume that.

    And of course now I'm also wondering if the discarded 17" can just be fixed by a new cable.
     
  11. MacTech68 macrumors 68000

    MacTech68

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    #11
    The AppleVision extension provided geometry adjustments via the ADB port on older "AppleVision" monitors and should be easily disabled without causing additional problems. However, if you're able to get up to 1024x768 then installing it seems unnecessary.

    Yup, which is essentially the sense code for a 16" Apple Multiscan monitor.
    [​IMG]
    [​IMG]
    Sense0= Pin4, Sense1= Pin7, Sense2= Pin10
    Note from the above "Table 1" that with the diode in one direction you get 16" Multiscan and 3 available resolutions. If you reverse the diode you get 21" Multiscan and 4 available resolutions. Note that you MUST reboot for the new sense code to be recognized.

    Yup, it's quite possible that the green pin (or green return) is open circuit. But it could be anything in the green path, all the way to the RGB amplifier and sometimes can be as simple as a dry/cracked solder joint. If you remove green, you'll get pink as can be seen in the additive properties of light:

    http://en.wikipedia.org/wiki/File:RGB_illumination.jpg

    If it's an AppleVision 1710 or 1710AV forget it. they were littered with dry joint problems from day one! No sooner have you fixed one fault, another develops. :mad:

    Sense codes can be real fun when you get older odd-ball monitors (like old Sony 21"/IBM/SUN) that don't use VESA standards. :eek:
     
  12. HavingFun, Jun 10, 2011
    Last edited: Jun 10, 2011

    HavingFun thread starter macrumors newbie

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    #12
    Yup, did do that.

    Had one. Picked up around 2002. Their reputation was so ghastly I wondered if it might be the only one still running. I got about two years out of it, before that it was in daily use at a university lab.

    This one's the M2494. The one that always has a broken control cover.
    http://www.everymac.com/monitors/apple/multiple_scan/specs/multiple_scan_17.html

    Splendid info, btw. Very helpful.


    Edit: Confirmed the Apple monitor cable a diode from 7 to 10 in the connector.
     
  13. MacTech68 macrumors 68000

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    #13
    Ahhh... If you're handy with a soldering iron in tight places, resolder all smd resistors on the left hand side (looking from the front) of the CRT neck board.
    They are on the same side as the heat sink and are dotted around (very close) to the heatsink. Tapping the board with a well insulated screwdriver should reveal that the cracked solder joint is there.

    I did probably 6 or 7 of them 'way back when'.

    And yes, we priced the door for one years ago (when they were worth something). Apple AU wanted AU$123 for one. I must get into injection molded plastics. :D
     
  14. HavingFun thread starter macrumors newbie

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    #14
    Excuse me a moment for the obligatory addition:

    ==STANDARD IMPORTANT WARNING==

    CRT displays contain hight voltages even long after they are unplugged. High voltage can easily hurt you badly and even kill you. Do not open CRT displays. Seriously, do not just read about it online and "give it a go" -- CRT work is for specifically trained people only. It's way too hazardous to experiment with.

    I hope that's clear enough. Really folks, don't mess around inside the old monitors and televisions.

    ==============================

    Had a look at that two or three times already, trying to figure out the pink business. It always kind of bothered me that that didn't fix things, and now I find it was the cable all along.

    Anyway I'll have to come back to this. This is a pottering hobby; not something to spend money on. It may be a while before I find the right bits in my scrap boxes. Just wanted to get the Warning up before I forgot.
     
  15. HavingFun thread starter macrumors newbie

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    #15
    Well, this is a little strange.

    And all in pink.

    The cobbed cable this time is just a gameport to a serial trimmed to DB15 size. It's wired straight through, plus the diode.

    It's interesting that it recognizes the G78 by name with 10>7. It's also interesting that none of those results match the table. And then, there is that resolute pink problem too.

    Tried the NEC again for sanity-check, and it's just fine.
     
  16. MacTech68 macrumors 68000

    MacTech68

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    #16
    Hmmm..... If the 7600 actually shows the G78 name in the Mac's control panel then there must some DDC or EDID going on. The data is via Pin 12 on the SVGA connector. What pin is that connected to on your cobbed adapter?

    In which case, using the diode may not be necessary.

    I hate to ask so late, is this using the on board video card or a PCI video card?
     
  17. HavingFun thread starter macrumors newbie

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    #17
    The cobbed portion is straight-through DB15-DB15, plus diode. The store-bought DB15 to SVGA passes the SVGA 12 to Apple's 10.

    The Apple's using onboard video.

    Is there something that would tell us what driver software is being used? Or firmware? Perhaps it's had an update for newer displays, though it couldn't be a very good at it because that's the trouble in the first place.
     
  18. HavingFun thread starter macrumors newbie

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    #18
    It's over. I broke the mac.

    I tried putting leads on the Apple's DB15 at the motherboard for 10 and 7, in order to get away from these cobbed adaptors, and hopefully that pink.

    I got no display instead. The Apple did not try to go into startup after the initial hdd noises. I removed the leads and got the same. Probably I either ruined something with too much heat, or i bumped something in the award-winning case design.

    Sorry about that. The question had become interesting enough that we really deserved to see the bottom of it.
     
  19. MacTech68 macrumors 68000

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    #19
    Before you chuck it all away, it's possible that the PRAM or CUDA have become upset. PRAM stores the last Sense Codes used and when powered up compares that to the current sense codes. If they don't match the display resolution reverts back to the lowest resolution (if a multisync) ie 640x480.

    Resetting Cuda:
    http://support.apple.com/kb/TA39568

    This post should give you the location of the CUDA reset button:
    http://68kmla.org/forums/viewtopic.php?f=12&t=9480#p94876
    another reference for what's where:
    http://www.mathdittos2.com/images/010722-02-010labeled.jpg

    Resetting PRAM:
    http://support.apple.com/kb/HT1379

    Sometimes if the PRAM settings get scrambled, POST halts and the machine appears to be dead.

    Check the PRAM battery (small 3.6v 1/2 AA size) in circuit. If it's below about 3.2 volts, remove it and let the machine sit without mains power overnight. Running it without a battery is fine but date & time (and some other settings) will reset to default each time you power off.

    Also, the CPU cards Memory ad VRAM DIMMs suffer from poor connectivity. Cleaning the edge-fingers and slots may be necessary. To test connectivity, I would usually allow the machine to boot until there is no disk activity (better yet disconnect the Hard Drive and boot from a CD). Then, move the mouse in a circular motion, and rock the CPU and Memory DIMMs one at a time in their sockets. If the mouse pointer on the screen freezes, that socket/card needs cleaning.

    It gets pretty ugly when I think of all the possibilities. :eek:

    It's really up to you how far you want to go. :)
     
  20. HavingFun thread starter macrumors newbie

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    #20
    Great advice, and sorry it's so long getting back to it. Real life has been ripe and full.

    In the end, no luck.

    Yup, battery was 0.00 volts. Have not left it overnight yet, but did refill the coffeemaker. Have you really had a Mac hold trace charge more than a few minutes? "Overnight" is just so unusally generous that I'm thinking you must have an example or two in mind, and I'd love to hear it.

    ...it's not because of the charge in the monitor, is it? I wouldn't have thought that would feed back into the signal portion of the circuit at all.

    Re-seated everything.

    CUDA - the Mac does shut down after pressing the reset, but this changes nothing.

    PRAM - no effect at all from holding down Command-Option-P-R.

    Nor any lights on the keyboard other than the flicker when pressing the On switch.

    I'm thinking it's a well-sorted box of spare parts now.
     
  21. MacTech68 macrumors 68000

    MacTech68

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    #21
    Does sound dead but I hate to diagnose remotely. Trying to 'minimize' the setup is always your first best bet (ie, one stick of RAM, re-seat/clean CPU card RAM etc as noted before, no HD no CD no Keyboard/Mouse).

    I've seen PRAM get so badly corrupted as to make a machine appear dead, especially on the LC475, PowerMac 6100, PowerMac 7220 (4400 in A-Pac) and a few others so it is possible. Sometimes I would routinely remove all power sources, remove the battery and jumper the battery socket terminals overnight just to be sure. It did revive quite a few machines but not all.

    Maybe you can find it a good home at your local mad scientist's lab. :D
     
  22. HavingFun thread starter macrumors newbie

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    #22
    Yup, I can understand that.

    When restarting in stripped-down mode, should it be with the dead battery in, or removed, or removed and contacts jumpered?

    That's... probably here.

    I think worst is it'll end up in the back of the closet, rather than included in the recycling pile. It's exceedingly unlikely that I'll trip over another 7600, but spares for them are just so hard to come by that I'd feel awful if I did & didn't keep this one. Also I'm starting to regret chucking the system 7 stuff I chucked as "no-one will never want again." It's like my dog-eared Osborne. Eventually some goofball is going to be very happy that I kept all the manuals and bits boxed away together - and that's enough to give it a little real estate. I understand that kind of fun.
     
  23. MacTech68 macrumors 68000

    MacTech68

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    #23
    Battery removed, no jumpering.

    Yup. I still remember the day we threw about 50 Mac128, 512 & Plus cases in a skip-bin. :(

    I only want one Mac128 case since the one I have had a label removed with what appears to be a scourer. :eek: That lovely textured finish is gone. :(

    But, half my house is crammed with old Macs. I'm just lucky enough to have a geek GF. :eek:

    I did chuck a TRS80 that I now wish I'd kept, and some Apple II bits like dual 8" drives and some other gear but I kept a II, II+ and II Euro+. :)
     
  24. HavingFun thread starter macrumors newbie

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    #24
    Alas, no. No change. Tried different sticks and various other combinations just in case.
     
  25. chrismacguy macrumors 68000

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    #25
    As far as testing the "bits" of a 7600, what can be a decent way of testing the big components (CPU and DIMMs), are to try and find a 7500 and throw the CPU and DIMMs into it. (My 7500/100 is actually a 7600/132 CPU on a 7500 Mainboard with a boatload of RAM, and that thing performs fine, even if it is a bit of a frankenmac, but it lets you test everything at least works internally, as IIRC the 7500 and 7600s guts are incredibly similar, just with a 604 over a 601 - and if the CPU works and the 7600 is dead you can always move all the bits into a 7500 and use it as before, and for some reason 7500s seem to be more common in my experience).
     

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