Macintosh Portable power regulation

[Mc128k]

I did not add diodes, they were pre-built in the cable, an official "Apple Hack". They are for both protection and voltage dropping, I can't remember their type, but any rectifier I think will do fine, they don't need special features. They were the black type, not the glass ones.

 

[Raoul]

Hi 
I found your topic searching for "Macintosh portable Q16". I've opened my Portable for the first time yesterday, because I wanted to recap it after some years in my attic. One of the last time I used it, many years ago, I have tried to install the Com card, and instantly I've got a burn smell. Shut the Portable off, removed the card, booted it again, and it was still working.
So today I've checked the card : light corrosion near the ports, one capacitor seems leaky, and Q16 seems fried.
So I've some questions, and here seem one of the best places to get an answer
I don't want to do more damages.
• Do you think after recap I can boot it securely without changing Q16 ?
• Do you have the reference for Q16 ?
• I'm not an expert, and not used to such heatsinks, what's the best protocol to remove Q16 ?
I thank for any answer.
Raoul

 

 

[techknight]

Doesnt look fried to me. Just blackening on the heatsink plating from corrosion. Thats it. 

 

[Raoul]

For my Q16, it's not corrosion, but overheating.
Reading again the full topic, I'm wandering if the culprit was not the Com card, but me (I don't remember exactly, it was a very long time ago) using a grey power supply in place of the white one.

 

[glay78]

What’s the symptom of a failed Q16?

 

[techknight]

For my Q16, it's not corrosion, but overheating.
Reading again the full topic, I'm wandering if the culprit was not the Com card, but me (I don't remember exactly, it was a very long time ago) using a grey power supply in place of the white one.

No it isnt. I was replying to your post. 

Your Q16 heatsink is blackened from tarnish/corrosion. Not heat. 

That is not to say that the transistor got hot over the years, but the blackening of the heatsink is due to tarnishing. 

 

[techknight]

What’s the symptom of a failed Q16?

Dead machine. its the 5.2V regulator. 

 

[glay78]

Dead machine. its the 5.2V regulator. 

ok great thanks! 

 

[techknight]

ok great thanks! 

If it shorts, it'll send 6V to 7.5V to all the 5V chips which would fry everything up stream, basically bricking the board. I have seen it. its rare though. The first thing it takes out is the SWIM, and a handful of 74 series logic next to the CPU. 

 

[glay78]

If it shorts, it'll send 6V to 7.5V to all the 5V chips which would fry everything up stream, basically bricking the board. I have seen it. its rare though. 

because sometimes after I run my portable from start to sleep cycle and a few times within an hour or so , it will register as low batt even the batt is fully charged. It will then go to sleep to prevent batt from draining. I’m not too sure what’s causing it.

 

[techknight]

because sometimes after I run my portable from start to sleep cycle and a few times within an hour or so , it will register as low batt even the batt is fully charged. It will then go to sleep to prevent batt from draining. I’m not too sure what’s causing it.

Thats a bad PMGR/Hybrid. Very common, and short of that, could be caps/resistors support components in the circuitry between them. 

 

[glay78]

Thats a bad PMGR/Hybrid. Very common. 

It’s a backlit. Actually I can live with it. It runs well still.

 

[techknight]

It’s a backlit. Actually I can live with it. It runs well still.

Oh, that makes it even more fun to figure out. :-/

The power supply stage is VERY different than that of the 5120. 

 

[glay78]

Oh, that makes it even more fun to figure out. :-/

The power supply stage is VERY different than that of the 5120. 

Yes I know, that’s why I will just live with it.