Mac Portable backlit, wont power on HELP

[Gary119]

Hello everyone,

I have a Macintosh Portable, backlit M5126 model. When I first purchased the unit, I utilized a new 6.4 v 4.5ah battery to replace the old dead main battery. Furthermore, I replaced the 9v secondary battery. I tried powering the unit up, and it did nothing. Upon a first disassembly I located numerous bulged/leaking caps, the board overall was dirty as well. I removed all SMD/through hole caps, I then washed the PCB, and baked out all of the moisture in the oven (170-185F, for 20-25 minutes). Upon confirming that the PCB was dry, I recapped the entire PCB. Once I conclude the recap, I reassembled the computer and attempted to boot after holding the reset & interrupt switches. Upon trying to boot, again, it did NOTHING, no chime, no HDD noise, nothing. It was as if the board wasn't getting power, it also wouldn't display anything on the screen. 

There was some surface crud that gathered on top of several traces. I've tested all questionable looking traces, and each one does in fact have continuity. I previously inquired on this forum as to what I could look for, and I was informed that it could be bad traces/connections near the reset/interrupt buttons. I checked everything and nothing appears out of order. I've tried to find schematics for the M5126 model, but I've been unsuccessful in my attempts. For clarification, after cleaning the board, I've noticed some residual grime that has stayed on the surface, I need to find a sure fire method for cleaning PCB's. 

I guess this post is just me reaching out to anyone that has any input on the matter, or could offer guidance. I'm new to restoring computers, I'm accustomed to cleaning/maintaining game consoles, which I've amassed a collection of. 

Thanks everyone,

Gary.

 

[techknight]

you press the NMI and reset buttons to reset the PMU. 

then you press like the spacebar key to get it to turn on. 

If it doesnt power on, there is likely damage somewhere in the voltage regulation circuitry near the two buttons on the logic board. This is a common issue on the M5126. Repair success is very hit or miss. More miss than hit, as I have a pile of junk boards from similar issues. Either unable to maintain regulation, or no power at all. 

Also the M5126 has no publicly available schematic. Only the M5120 which is unfortunate becuase the power regulation circuitry is very different between the two. 

Best thing is to put a multimeter on the main voltage regulator and verify your getting 5.2V out of it. if not, theres your issue. That circuit is hot all the time no matter what. 

Also. Dont take this the wrong way, but the Macintosh Portable, especially the M5126 is NOT the best candidate for restoration as a beginner. Actually, these machines are for the more advanced. 

you really have to learn electronics troubleshooting and repair before you can attempt a machine like this. Also, you already have a thread on this machine. Why create a new one? If this is the same machine that you already posted in another thread here, with its pictures, then this machine is in really poor shape and will require a seasoned electronics technician to really figure it out and fix it. and as I said, even then, its a 50/50 shot. 

 

[Gary119]

you press the NMI and reset buttons to reset the PMU. 

then you press like the spacebar key to get it to turn on. 

If it doesnt power on, there is likely damage somewhere in the voltage regulation circuitry near the two buttons on the logic board. This is a common issue on the M5126. Repair success is very hit or miss. More miss than hit, as I have a pile of junk boards from similar issues. Either unable to maintain regulation, or no power at all. 

Also the M5126 has no publicly available schematic. Only the M5120 which is unfortunate becuase the power regulation circuitry is very different between the two. 

Best thing is to put a multimeter on the main voltage regulator and verify your getting 5.2V out of it. if not, theres your issue. That circuit is hot all the time no matter what. 

Also. Dont take this the wrong way, but the Macintosh Portable, especially the M5126 is NOT the best candidate for restoration as a beginner. Actually, these machines are for the more advanced. 

you really have to learn electronics troubleshooting and repair before you can attempt a machine like this. Also, you already have a thread on this machine. Why create a new one? If this is the same machine that you already posted in another thread here, with its pictures, then this machine is in really poor shape and will require a seasoned electronics technician to really figure it out and fix it. and as I said, even then, its a 50/50 shot. 

Thanks for the response Techknight,

This IS in regards to the same machine I posted the pictures of in a previous thread. Also, the reason I made a new thread is due to the fact that this branch of the forum is intended for Mac Portables and up, I now realize that the previously used forum section wasn't intended to have subject matter pertaining to Mac Portables. 

I notice there is a small VOLT REF chip by the op amp, a larger chip that's labeled "VOLT REG" by C206, there is also what appears could be a regulator inside Q16. Which should I test?

Thanks, Gary.