Another Mac Portable Thread :) Seemingly no power to drives

[JAMMARob]

Howdy!

I am in the process of restoring a Macintosh Portable (5126) I recently picked up from a former Apple employee. Taking the advice of the forum, I immediately rebuilt the battery with new EnerSys Cyclon X cells and replaced all of the capacitors on the logic board. The leakage and corrosion was fairly extensive, especially around the large axial cap near the sound section.

When assembled and tested (with original AC adapter and rebuilt battery), the portable powers up and appears to work properly, however, the floppy drive makes a constant low-pitch whine (there is an unknown disk in the drive) and the hard disk appears to do nothing. The portable posts to the blinking question mark.

There is also no sound from the speaker. I have yet to check the headphone jack.

I suspect a power issue. Are there a couple of components I should check first? I recall some corrosion near the LT1070 converter.

 

[IlikeTech]

Pull the hard drive and test for voltage at the molex conmector?

 

[techknight]

Pull the hard drive and test for voltage at the molex conmector?

Good thought.... But... Not valid in this Case.... 

Anyways... You need to check your 12V rail, and make sure you replace the through-hole capacitors as well as the SMD ones. Some people replace the SMD caps and forget the little through hole guys! Ive seen it... 

Once you confirm you have changed every single capacitor, I would monitor the 12V rail. there could be a failure in the diode, or even the switching regulator IC. 

 

[JAMMARob]

DEFINITELY changed all of the caps, even thru-hole. In fact, the thru-hole caps had leaked the most. 

I'll start at the LT1070 and work my way down the circuit!

 

[techknight]

the whining noise is what has me thinking the LTC1070 or one of the new caps didnt catch the connection. 

 

[unity]

Careful with polarity? I think the Portable has a couple "gotcha' caps that are opposite position of its neighbors.

 

[JAMMARob]

Interestingly enough, when I inspected the board again, I noticed that the diode at D1 was super crusty and underneath the LT1070 was a lot of capacitor juice! The diode fell off of the board! I was able to clean it and repair the pads to solder it back in place.

Tested and now I have sound and no more whining from the disk drive!

But the "sound" is just noise, like the bus traffic, or kinda like an incoming fax. The floppy now tries to eject but needs some help. Still nothing from the hard disk. It seems like the drives aren't getting enough power.

More troubleshooting tomorrow

I still suspect there could be a problem with the LT1070.

 

[JAMMARob]

So I decided to clean the board, dry it, and let it dry under a fan overnight after seeing the cap goo under that regulator. I am back to no sound, but the hard disk spun up for about 10 seconds, then spun back down. Disk drive still isn't whining but didn't have time to test it further. Maybe there is no OS on the drive and it spins down if it's not a viable boot device? I guess it's time to make a boot disk!

 

[bibilit]

Or the Disk is dead...

 

[JAMMARob]

Hoping that's not the case! I'll create a boot disk and try to start it, then figure out why I am not getting any sound.

I haven't been using a PRAM battery during testing. Should I be?

 

[bibilit]

No, the sound should be there anyway.

 

[techknight]

there is no sound because the traces are broken from the two 47UF caps to the sony sound ICs. common common common... 

 

[JAMMARob]

Gotcha. I will investigate further and report back!

 

[JAMMARob]

Looooot of dark traces on the underside of the logic board near the sound section. Gonna be fun checking all of these connections!

 

[techknight]

Also, using a magnifier and a flashlight, Shine a light through the board and check the annular rings around the Vias, they love to get eaten away too.