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Mac IIx Mainboard Repair

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Hello,

 

I recently tried to recover an old IIx. When I jump started it the first time, no sound came up at all, not even the dead one. So I swapped all the SMD electrolyte capacitors and cleaned the Mainboard with alcohol. Now it brings the broken sound after jump starting, nothing else. The ROM module is in place, tried with four or all eight RAMs which were installed, same result, just the broken boing. And no video output.

 

Where can I continue to debug now? What are other typical broken parts in those machines.

 

Thanks in advance and best regards,

 

Florian

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If your willing to send a highres picture of your logic board many in the forum enjoy looking for bad traces and such. Does your video card have electrolytic caps on it?

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My guess is bad traces also. I have a IIx board that looks nice, until one looks close. I have it as a future project but expect it will never boot. Its a pretty common issue on the IIX, something to do with where the boards were made.

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If your willing to send a highres picture of your logic board many in the forum enjoy looking for bad traces and such. Does your video card have electrolytic caps on it?

I'll do some hires pics later.

The Video Card (Apple Computer Macintosh II Video Card) has only non-SMD caps which look OK.

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Try booting it without the video card.

 

And which video card is it? I have all 3 that Apple made for the Mac II Series and they all have SMD/SMT caps on them

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Hi folks,

without video card it is the same, just the dead boing. I tried the video card in all NuBUS slots, no difference.

 

Thanks.

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It would appear you did a decent soldering job. The pics are not high enough resolution to pick out tiny details, but nothing stands out. Caps appear in place, etc.

 

I would check power supply voltages.

 

Also, what an odd board with that battery board. The IIx is designed for proper battery holder right on the board OR direct wire style. Mine had normal mounts, like on a IIfx, etc. Weird for me to see that.

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You can download the pics in original resolution when you click on the small cloud beyound the picture (in the center of the screen), just doublechecked you can even read the partnumbers on the chips and caps.

This cloud solution from my webhoster is not that optimal, I know.

If you already tried this, I can take better pictures tomorrow.

 

I already checked the power supply, its OK, ripple is < 0.1V

 

Thank and good night,

 

Florian

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That is what I did. But the pics have a soft focus and are still not high resolution enough. You probably need to take at least 4 close-up pics, divide the board up basically into areas for pics.

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The battery board upgrade was common, mine have them.

 

What size RAM modules are those? Stick with a known good set of 1MB/each and 8 chip non parity will work.

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Im watching this with much attention as my IIx will jump start on, and shut down (normal) but start normal does not work.  I have read a bunch but the hand drawn schematics dont match what the board looks like and Im not getting the real idea how to check traces or I would just run new wires point to point, one at a time till I found the correct fault.

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there hasnt been a IIx board that I havent been able to fix. 

 

Most if not all of them turn out to be corroded/eaten traces near the IC behind the nubus slots. 

 

And there is 2 or 3 traces that run all the way across the board between that IC, and the switch that go bad too. 

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Hello folks,

 

thanks a lot for the help. Sadly the Mac is still dead. I rewired some of the broken lines, some looked bad and were OK. Checked them with my lab ohm meter. Are there some other tips to diagnose where the error is? The RAM is definitely OK my IIsi runs with it without errors. BTW I placed all RAM modules on the right field (BANK-A). Is this correct? Which NUBUS slot should be used for the graphics card?

 

Regards

Florian

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Hello folks,

 

when I place RAM in all slots now, I get the good chime. When I add RAM only to BANK A I still get the dead chime.

But the connected monitor only turns on and still no picture. Do you have any suggestions what to check next? It was no keyboard/mouse connected. Macs do not need this, right? The display is capable of the Mac VGA signal, doublechecked with my IIsi before, used the same adaptor.

 

Thanks in advance,

Florian

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adapters for the II's for some reason dont play the same.  I also had to recap the radials on all my II video cards.  None would produce signal.  The II needing a video card makes troubleshooting harder because of that.  No other macs that I recall require a card until the B&W G3's.  All have built in onboard video at a minimum.

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