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Mastergeko4

Macintosh Portable Troubleshooting

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13 minutes ago, techknight said:

You need to grab a digital multimeter and put it on DC Volts, take a monitor of the 5V rail and 12V rail to see how stable it is when all this happens, we need to see which rail is faulting. 

I feel stupid for asking, but where exactly am I putting the meter? 

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For the 5V you can clip the negative probe from your voltmeter to any GND point and then put your positive probe on pin 3 of MOSFET Q4 (at the top right as you look from the front of the PCB. This is always on so should show +5V even if the machine is shut down. Keep monitoring the voltage as you press a key on the keyboard to start the machine up. The voltage shouldn't drop.

For the +12V line, in the same area you will find the two Sony sound chips. Pin 13 on either of these is on the 12V line.

Edited by Stephen_Usher

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6 hours ago, Stephen_Usher said:

For the 5V you can clip the negative probe from your voltmeter to any GND point and then put your positive probe on pin 3 of MOSFET Q4 (at the top right as you look from the front of the PCB. This is always on so should show +5V even if the machine is shut down. Keep monitoring the voltage as you press a key on the keyboard to start the machine up. The voltage shouldn't drop.

For the +12V line, in the same area you will find the two Sony sound chips. Pin 13 on either of these is on the 12V line.

Thank you! I probed the pins on the chips you told me to do and I don’t think I found the issue. On Q4, it reads 4.9v and rarely 5v however this shouldn’t be that big of an issue. Meanwhile on both sound chips, the highest voltage I could get was 11.5v. I’m not sure if this is a huge issue but let me know as it could be the source of the issue. 

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The macintosh portable should solidly be providing around 5.2V. 

 

It sounds to me you are stiill having issues with the Hybrid IC. Sadly, this is a known issue and I have accumulated a handful of parts boards due to bad Hybrids. 

 

One last thing to check is make sure your 6V battery is good, AND the battery cover/door is slid and snapped into place. There is a microswitch in there that must make contact to provide the 6V into the logic board, otherwise itll try and run off the 9V battery if there is one. 

 

@Stephen_Usher You should take a look at the opportunity to clone and reproduce the Hybrid IC as a new PCB. I would do it, but im scrapped for time these days. 

Edited by techknight

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6 minutes ago, techknight said:

The macintosh portable should solidly be providing around 5.2V. 

 

It sounds to me you are stiill having issues with the Hybrid IC. Sadly, this is a known issue and I have accumulated a handful of parts boards due to bad Hybrids. 

 

One last thing to check is make sure your 6V battery is good, AND the battery cover/door is slid and snapped into place. There is a microswitch in there that must make contact to provide the 6V into the logic board, otherwise itll try and run off the 9V battery if there is one. 

 

@Stephen_Usher You should take a look at the opportunity to clone and reproduce the Hybrid IC as a new PCB. I would do it, but im scrapped for time these days. 

That's a shame that the Hybrid Board is dead but I kinda expected that. I think the last thing I'll try is to buy that battery @LaPorta listed on the previous page. I'll update you guys when I finally finish the project. 

Would there be any possible way to get a replacement Hybrid Board?

Thank you all for your help!

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Replacement Hybrids will have to be something we make. I ran out of them picking them from parts boards, and my other parts boards have bad hybrids.

 

I personally own 3 portables, and both non-backlit models have issues with the hybrid. They need changed out with new. I think cap goo gets in there and starts affecting the resistances of the laser etched carbon tracks on the ceramic substrate, or adds parasitic capacitance. But this is a wild guess. the components themselves that are physically soldered on the hybrid are usually ok. 

Edited by techknight

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17 hours ago, techknight said:

Replacement Hybrids will have to be something we make. I ran out of them picking them from parts boards, and my other parts boards have bad hybrids.

 

I personally own 3 portables, and both non-backlit models have issues with the hybrid. They need changed out with new. I think cap goo gets in there and starts affecting the resistances of the laser etched carbon tracks on the ceramic substrate, or adds parasitic capacitance. But this is a wild guess. the components themselves that are physically soldered on the hybrid are usually ok. 

That’s interesting. Would their be a way to make a replacement PBC using a website like PCB Way and then just transfer the components? 

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14 hours ago, Stephen_Usher said:

Electronically, what does it actually do?

 

It does many things. One, it servers as a -5V voltage inverter. it also serves as the op-amp and reference voltage regulator for the 5V rail. Also, it serves as a window comparator for charge controlling, Sets the system whether the AC adapter is plugged in or not, and if it senses the AC adapter plugged in, it enables the P-Channel mosfet in the rear to allow the 7.5V DC to pass through without a high RDS. 

 

It also detects for undervoltage lockout. so if the battery voltage falls below a certain point, itll lock out the VREG. so no 5V. 

 

if the 5V supply is not being regulated properly, 99% of the time its the Hybrid. 

 

also if the system is running and the System software doesnt detect if a battery is charging or not, its usually the Hybrid there as well. 

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One other thing I wanted to say. I was wondering if this burnt looking component on the board, Q16, would also be an issue. It looks and smells burnt compared to other similar components on the board so I’m thinking of replacing it. What do you guys think? 

15A2472A-9D8C-4D49-AAFB-1ED0BB5731FE.jpeg

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Q16 does control the +5V line, as can be seen in the circuit schematic that techknight posted above. Looks like at some point there might have been a short circuit on the machine and it overheated the component. The IR9230 components are cheap and relatively easy to remove with a hot air reworking station so if you can I would change it.

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