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Mac Portable troubles

MOS8_030

Well-known member
Congrats! Nice to see a Portable brought back to life. I'm working my way toward dragging mine out and seeing if it still works.

 

techknight

Well-known member
Never once have I changed an Op-Amp and it had actually fixed that. Makes me kind of hesitant. 

 
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redruM69

Active member
Never once have I changed an Op-Amp and it had actually fixed that. Makes me kind of hesitant. 
It makes sense to me.  If the opamp's output is way off, yet everything else checks out, then it must be toast.  I did swap Q207 at the same time, but it tested good once I had it out of circuit.
FYI, I replaced the original LT1179CS with a MAXIM unit.  $10 a pair on eBay.  Not sure what the original manufacturer was, but it was different.
I appreciate your time.  You were a huge help!

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techknight

Well-known member
Well I am just saying that I have changed a many of them for similar symptoms and never had any luck. Only time I ever fixed one was a no-output condition. You got lucky thats for sure. But I always changed them with the same part same company, linear technologies. 

 
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techknight

Well-known member
Possible, or the specs are slightly different and its working in that circuit. 

Who knows, these machines are highly finicky. I am just happy that is working ;-)

 

PaloAlto

Active member
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Hi Everyone,

I just want to thank everyone for their help on this project. I am slowly trying to bring to life all the old Macs/Newtons/Apple II computers (and a few NeXTs) that I ever owned. This was one of the first projects. I've been lurking on the site for some time just reading and re learning things that I've forgotten. The portable involved replacing the battery and getting the board recapped. Thanks to those who helped me with that. Thank you to Technight for patiently answering my questions. I did not have the technical skill to go any further on the project. However, I found redruM69 while solving a separate problem (a hard drive replacement for the portable) and he offered to break down my portable and see if he could fix it. What an incredible job he did. I can't recommend redruM69 enough. He kept me updated at every step along the way and when he ran into a dead end, found a way to solve the issue. Attached is the portable returned to me and running super fast due to a SCSI2SD hard drive replacement.

As someone very new to computer restoration, a big thank you to all the help everyone gives on the boards and in person. I for one very much appreciate it.

 
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MOS8_030

Well-known member
Terrific outcome!

I hear you about relearning forgotten things!

I'll be tackling my Portables soon. They've been in the closet for many years now.

 

redruM69

Active member
Update on this project.  I shipped it back to the customer and all was right as rain for a couple of weeks.  It then reverted back to the same symptom!  This board appears to be blowing opamps pretty quickly.
I think we've come to the conclusion that its best we wait for another board to pop up, and swap it out.  This one is just not reliable.

 

techknight

Well-known member
In order to back up that theory I would suggest lifting the output pins on the op-amp, and putting an ammeter in between to make sure the op amp isn't driving too much current, because that would cause an op-amp burnout, otherwise its not blowing op-amps. there is something else wrong as I said in the beginning. 

I haven't had alot of luck with boards that did this. at least not much. 

 
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PaloAlto

Active member
Thanks everyone for the help. I am certainly learning as I wade deeper into my pile of old Macs. This portable has been particularly frustrating because it actually worked for a few weeks without any problems. It is the M5126. As I look for replacement boards, will the main board of the M5120 work as a simple swap or do I need to find an M5126 board?

Thanks

 

techknight

Well-known member
You would have to make a display cable adapter in order to fit a 5120 board in a 5126, and then you need the inverter control card. 

I did full photo documentation of that card, as well as doing pinouts of both displays however I have had no time to compile the information into anything legible. 

 

PaloAlto

Active member
Time for an update. Thanks again to RedruM69 who tackled a new M5126 MB and got it recapped. Slipped it into my existing case last night and it worked right out of the gate. It did take some doing, but I now have a working M5126. I also have the parts of an "almost" working spare, including a German keyboard! If anyone ever solved for a replacement backlit screen cable please let me know.

This was one of the first projects I tackled. Since beginning on the Portable I've conquered (with tons of help from others) a couple of Lisas, Apple II/+/Plat/IIc, and a slew of 72xx. There is still a huge pile to get working, but so far so good.

 
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