Mac mini G4 1.42 boots to black screen.

[Dave 23]

   Hi-
        My Mac Mini 1.42 has suddenly started booting to a black screen. It chimes, the fan runs and the mouse and keyboard have lights but that's it. It will start up in target disk mode just fine and the drive mounts as normal.
    Is there any fix for this, or is it a GPU failure? (and is there a way to tell?) Machine was working flawlessly last time I used it (some time ago)...
       Any help/insights much appreciated.
                                                               D.

[Dave 23]

Okay so I pretty much tried everything I could think of- cleaned all connectors, stripped machine/cleaned RAM, every possible startup option, SMC/PRAM reset, CD start, etc. nothing changed.
  Then I took it to a repair store they plugged in their modern HDMI display- perfect graphics, no problems!

  SO... Last time I used this machine I was using an Al Cinema display A1081 with no problems at all. What has changed so it will no longer work? (same display is working fine with M1 mini)  Any suggestions to get the system to see the display again?

                        TIA, D

[IIO]

did you always use the same mini OS distribution? (v7 vs v8 vs v9?)

[Dave 23]

 The mini is running Ross' OS9.2.2 system.  It originally worked flawlessly with the 20" cinema display- don't know what happened, but now the display shows nothing.  However...

 The Cinema display still works fine when plugged into my G4 powerbook 1.67

  The Mac mini works fine when plugged into a monitor @ the repair shop yesterday

  Both items seem to be working ok, but don't want to work together for some reason- though they did in the past. Trying to find out what is causing this new behaviour...

    (Since last successfully used with mini 1.42 G4 the display has been used with a mac mini M1, via both HDMI and USB-C adapters... wondering if this could have reset internals on the display at some point?)

[FBz]

No change with video extensions under OS 9? (ATI vs. nVidia.) Same black screen when Mini booted into OS X (or from an OS X install disc)? No recent new software or app installs?

Display power light is “on” even when screen is black… and no flashing sequence of that indicator light?

Here’s something else you might also try.

Had one here that exhibited similar symptoms - and “found” somewhere that if you cover the two center connection pins inside the power plug with cellophane tape, the display then works fine.



That’s 10 pins total (5 per side / green arrows) but only the two middle pins (both sides) need be covered in this manner. Hopefully you can see in the attached pic where both have been covered with tape strips. AND that slim tape strip needs to cover ONLY those two pins all the way down into the plug.

[Dave 23]

  Hey thanks for that FBz- I had seen that I will try it tonight.  I don't have an OSX partition on the Mini , which may be (part of ) the problem. This, from
  everymac..
  "This display requires a Mac with a DVI port running MacOS X 10.2.8 or later or a Windows PC with a single-link DVI port"

   Puzzling- this worked fine, despite not running OSX- maybe the display treated the mini as a PC for while (?).  I tried starting from OSX install CD- nothing.
   The power light on the display remains dimmed when connected to the Mini- no flashes. My other cinema display (I have 2 identical) began to flash 3 short
   during testing - I read somewhere it means "incompatible display signal".

   My Powerbook running 10.4.11  has no problem at all using the display. M1 mini is fine too.

   All very strange that both displays give same black screen despite previously working flawlessly without any problem at all- and the  Mini displayed fine on a (PC) display yesterday..
   The only thing that has changed is both displays have recently been used with a Mac mini M1 (another set of problems!) and have been switched back and forth between ports/adapters/cables and generally messed about with trying to get the M1 to behave. The M1 produces a very degraded image with a lot of artifacts on one of the dual monitors (still a problem with the latest OS).

[FBz]

Yes while EveryMac notes BOTH of the following… I have many of these working under OS 9.2.2. So this is perhaps more than a bit confusing.

*This display requires a Mac with a DVI port running MacOS X 10.2.8 or later or a Windows PC with a single-link DVI port.

This model uses the industry standard DVI (Digital Video Interface) and consequently is compatible with all DVI-equipped Power Macs and PowerBooks, in addition to properly equipped Windows PCs.
Would Apple unknowingly cause such a possible hardware  “black screen side-effect” for those attempting to use these monitors, back and forth with an M1?

And as to whether or not the Mac mini M1 has the ability to change something internally within the monitors themselves AND that carries over (or back) to your G4 Mini - your guess is as good as mine and we may need to invoke the grey matter of our resident, video goo-roos here.
RE: "incompatible display signal”. I’d suspect that your monitor settings have somehow been changed within your mini… BUT without the ability to boot and view those particular settings… how would you know? Have another, different monitor that you can use and then check?
Seems that the video “signal” (now) from your G4 Mini is not the signal (changed or corrupted) that your A1081 expects - or now somehow requires. AND that the constant variable (change) here has been that both monitors have been connected to the M1 Mac Mini and now no longer work with your G4 Mac Mini.

What are the monitor settings of your Powerbook, running 10.4.11 - that these monitors still work with? Check and somehow compare w/ G4 Mac mini.

[Dave 23]

  Completely agree with all your conclusions. Unfortunately I'm locked out of the G4mini for now so I can't see the display settings- I did trash display and monitor preference though, did nothing.. Also tried setting display to a low resolution with M1 before trying with G4...same..
  Powerbook w/ 10.4.11  goes very nicely with the display, very crisp, all settings available. (How the G4 used to be ... )
   I'm going to try the G4 with a friend's Cinema , I don't have any other displays to try it with. Will post results in case anyones interested...
    Thanks for the input!

[Bolkonskij]

FBz mentioned this before, but can you burn a physical CD with the Tiger OSX Install CD 1 and try to boot the Mini from it?

If the display springs to life, it might help to narrow down the problem to the OS9 side of things (or Apple doing mean things to older OSes/hardware)

If not, that might point into the direction of a hardware problem on the side of the Mini? (odd though that it worked at the repair shop ...)

[Dave 23]

 I tried this using a Panther 10.3 install disk- nothing changed. I am going to try a friend's Cinema display to determine if it's A) ALL cinemas or  B) just MY cinema...
A) meaning the G4 mini has changed, B) meaning my displays have changed.

Also going to try the (totally working) repair shop scenario- a PC monitor via a DVI to HDMI adapter. 
Wondering also, if using PC/HDMI cables/adapters with my Cinema may work.
Last resort is take G4 to store, find a cheap display that works and...buy it.   
Frustrating knowing it all worked beautifully not too long ago.

[Dave 23]

Progress report:
                       So I tested the mini with a third cinema display, and got exactly the same result- NADA.
 
        This confirms it's not just my Apple display that doesn't work w/ mini, it seems to be all Apple displays.
    The mini displayed just fine again when plugged into a PC monitor.
 
    I now have 2 questions. Why did the mini WORK with the Apple display originally?   and..

                           Why will it no longer work with ANY Apple (cinema) display now??
Being higgrent of what's going on under the hood, does anyone have any idea of what's going on here? TIA
 

[FBz]

Best guess here would be something missing
or disabled in your CPs or extensions.

The working “PC monitor” connected via DVI too…
or are you using an adapter?

Six of the Apple A1081 monitors in use here with…
G4 & Core2Duo Minis, MDDs, Quicksilvers & B&Ws.

Two files attached of a G4 Mac mini’s extensions
and control panels (basic setup here). Hopefully
you can open one of them and compare with yours
while you still have that PC monitor?