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Troublesome Macintosh Portable M5120 - Need some help


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I will be the first to admit, I don't know a ton about Mac Portables. This one came in pretty much dead. I am powered it through the molex connector, yes @techknight I have it powering both 1 and 3 :p

So I now have the system turning on and booting, however it doesn't ALWAYS do that. Here is what it does:

  • Sometimes if I power it up, it does nothing - amp draw goes from 0.20 slowly to 0, no display
  • Boots up fine - boots great, shows flashing floppy icon
  • Boots up to crash screen -- If I use reset button, this will happen 4-5 times in a row
    • Powering off and back on can resolve faster but that's not guaranteed

 

So this smells like badly performing. But since I don't know the portable that well, I figured I'd come ask the more knowledgeable. 

 

Additionally these is a horizonal line, single row but half the screen. I pressed on the various chips on the back, no difference. I assume this is a internal ribbon issue?

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Bad Hybrid. I bet it doesn't indicate charging properly either. 

 

the line on the screen is just a bad screen. 

 

If I can get the time and energy, i need to finish the hybrid replacement. As I had mentioned in other threads, what happens is the capacitor goo gets into the ceramic substrate and into the printed carbon film resistors and alters their values, which breaks the whole circuit. 

 

 

Edited by techknight
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21 hours ago, desertrout said:

Well, the first question has to be: has the logic board been recapped and cleaned?

Yes, the board is recapped and there wasn't anything on the board to be concerned about. It was concentrated under the caps themselves. I might ultrasonic it just in case, but the hybrid is CLEAN.

 

20 hours ago, techknight said:

Bad Hybrid. I bet it doesn't indicate charging properly either. 

 

the line on the screen is just a bad screen. 

 

If I can get the time and energy, i need to finish the hybrid replacement. As I had mentioned in other threads, what happens is the capacitor goo gets into the ceramic substrate and into the printed carbon film resistors and alters their values, which breaks the whole circuit. 

 

 

Not sure that's true here, the hybrid is very clean. There wasn't major leakage on this board.

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19 hours ago, Amiga of Rochester said:

 

Not sure that's true here, the hybrid is very clean. There wasn't major leakage on this board.

 

Doesn't mean anything. This is definitely bad hybrid behavior. There may be other causes, but I have yet to run in one. (not to say its impossible)

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19 hours ago, techknight said:

 

Doesn't mean anything. This is definitely bad hybrid behavior. There may be other causes, but I have yet to run in one. (not to say its impossible)

Well that sucks. What's stopping the reproduction? If it's a faulty hybrid it has to be a bad transistor or something. Got a pin out of the hybrid so I can look at its voltages? 

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20 hours ago, techknight said:

If I can get the time and energy, i need to finish the hybrid replacement.

 

I'm fairly certain that if you manage to pull this off, you will be in the Mac Hall of Fame.

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20 hours ago, Amiga of Rochester said:

Well that sucks. What's stopping the reproduction? If it's a faulty hybrid it has to be a bad transistor or something. Got a pin out of the hybrid so I can look at its voltages? 

 

Getting the correct resistor values for one. Someone else has managed to draw up the schematic of the card already. trouble is, I already know he has issues with some of the measurements he took of the values. Like i said previously, thats what causes these things to malfunction. the resistor values get affected by cap juice. Whether it looks "clean" or not, its there... Or was there. 

 

I need to study the mathematics of the design against the resistor values to make sure the ones I read, are accurate. if not, adjust accordingly. There are precision divider networks and reference set points that are super critical on how the circuit operates, keeping the 5V regulated and stable, keeping it In and Out of charge mode, as well as low voltage lockout. 

 

In some cases the PMGR goes bad too, but not nearly as often as the Hybrid does. Either way, you need a parts donor board to swap the PMGR to see if that solves your issue. 

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19 hours ago, techknight said:

 

Getting the correct resistor values for one. Someone else has managed to draw up the schematic of the card already. trouble is, I already know he has issues with some of the measurements he took of the values. 

 

I need to study the mathematics of the design against the resistor values to make sure the ones I read, are accurate. if not, adjust accordingly. 

Any way I can confirm the hybrid is the issue? I just can't imagine where the fault is and would like to try and identify it. I've informed the customer its likely the hybrid and they understand. I did very thorough job of checking the vias when I removed the caps. Checked traces too :) We do a pretty detailed job. If it is what it is, then not much I can do but I'd like to rule everything out.

 

PS: Down to talk one on one sometime? Feel I could learn a lot from you. Even just IM would be cool.

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19 hours ago, Amiga of Rochester said:

Any way I can confirm the hybrid is the issue? I just can't imagine where the fault is and would like to try and identify it. I've informed the customer its likely the hybrid and they understand. I did very thorough job of checking the vias when I removed the caps. Checked traces too :) We do a pretty detailed job. If it is what it is, then not much I can do but I'd like to rule everything out.

 

PS: Down to talk one on one sometime? Feel I could learn a lot from you. Even just IM would be cool.

 

you can swap the PMGR IC with a known good one to rule that out. 

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19 hours ago, Amiga of Rochester said:

Hmm, I don't have another portable or parts, are these found on any other macintosh boards?

 

Powerbook 100. That's it. 

 

There are 2 caps right next to the PMGR, and the cap goo can actually wick up inside the chip and cause the chip to malfunction. Epoxy to pin bonding on ICs aren't solid. it will migrate. 

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19 hours ago, techknight said:

 

Powerbook 100. That's it. 

 

There are 2 caps right next to the PMGR, and the cap goo can actually wick up inside the chip and cause the chip to malfunction. Epoxy to pin bonding on ICs aren't solid. it will migrate. 

Board didn't have any goo anywhere, pins of all chips are shiny and not dull / matted. I know this isn't definitive. I'm just being as detailed in my information as I can.

Does the pmgr cause it to crash? That's the part that's odd. I can hit reset 5 times and the system could crash 4/5 or boot. 

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19 hours ago, Amiga of Rochester said:

Board didn't have any goo anywhere, pins of all chips are shiny and not dull / matted. I know this isn't definitive. I'm just being as detailed in my information as I can.

Does the pmgr cause it to crash? That's the part that's odd. I can hit reset 5 times and the system could crash 4/5 or boot. 

 

Yes it can, it constantly communicates with the VIA. Any issues here, the drivers could do strange things. Also, the Hybrid can cause it to crash too. if the 5.2V supplying the system is unstable/noisy. 

 

Any details on the crash? 

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19 hours ago, techknight said:

 

Yes it can, it constantly communicates with the VIA. Any issues here, the drivers could do strange things. Also, the Hybrid can cause it to crash too. if the 5.2V supplying the system is unstable/noisy. 

 

Any details on the crash? 

I want to be clear, crash = on boot. Does not show mouse at all. If it shows the mouse, it's very stable and doesn't crash. Haven't use my SCSI2SD yet but planned to so I can see where it gets

I will measure the voltage during this crashed state. I was thinking ram not getting enough voltage.

I've replaced all caps with FK series Panasonic SMD and HE nichi or FR Panasonic for through hole so I know I'm good there.

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20 hours ago, Amiga of Rochester said:

I want to be clear, crash = on boot. Does not show mouse at all. If it shows the mouse, it's very stable and doesn't crash. Haven't use my SCSI2SD yet but planned to so I can see where it gets

I will measure the voltage during this crashed state. I was thinking ram not getting enough voltage.

I've replaced all caps with FK series Panasonic SMD and HE nichi or FR Panasonic for through hole so I know I'm good there.

 

I was asking for details on the crash. What kind of crash is it. Sad mac code? etc....

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20 hours ago, Amiga of Rochester said:

Ah, it's not analog it's digital. sigh. ill just have to do the best i can then to read the error...

 

I was going to say, it should be fairly clear unless something is seriously wrong with the graphics circuitry. 

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