Jump to content

Macintosh Portable power regulation


Recommended Posts

  • Replies 52
  • Created
  • Last Reply

Top Posters In This Topic

Two follow up questions.

 

What is the situation when your floppy drive won't boot and runs slow? I've seen two boards doing that now. Scsi boots fine. Machine is happy Mac otherwise. Internal and external floppy ports suffer the same. Even a floppyemu won't work. Is there an ic to blame?

 

What does the 16-18 pin 1k resistor trick do, when should I use it?

Link to post
Share on other sites

Two follow up questions.

 

What is the situation when your floppy drive won't boot and runs slow? I've seen two boards doing that now. Scsi boots fine. Machine is happy Mac otherwise. Internal and external floppy ports suffer the same. Even a floppyemu won't work. Is there an ic to blame?

 

What does the 16-18 pin 1k resistor trick do, when should I use it?

 

 

About the floppy I would start a new thread, as this isn't related to power regulation. I haven't investigated on it, but if you follow the first scheme I posted you should be able to check if there is power first.

 

16-18 as you can read from techknight's posts is a hack that kickstarts the IC chip into oscillating. As this is a power-saving IC, it compares the values periodically, and not in a continuous mode. Sometimes it gets stuck it seems, and this trick gets it back to checking the input values. Check out the datasheet if you need more info.

Link to post
Share on other sites

Another thing, just to update the topic. The lead-acid cells have arrived and I reassembled the battery pack. It just works perfectly, so absolutely no IC/FET/Transistor was harmed during my awful experiments.

 

So... it is done now. Everything in full working order, just like new.

I also see that using the bench power supply the computer actually asks for more than 1.5A, so a limiting power brick is mandatory in every case. Like somebody wiser said.. do not use the gray brick. Ever.

Link to post
Share on other sites

Can you post some details on your workbench setup? How are you powering the mac? What voltage exactly? Using the original wires?

The portable is a bitch with power control and regulation, most problems can be hunted down to incorrect usage I think.

Link to post
Share on other sites

it shouldnt.

 

But I do know that on those machines, if 1 of the 2 red wires loses voltage, it can fry the SWIM, I have witnessed it first hand. 

 

what it does it cause the 5.2V to lose regulation, and will show AC adapter voltage at 7.5 to 7.8VDC, and the SWIM gets hit first. 

 

And to be honest, after following a couple threads, the wiring harnesses are starting to become problematic, Whether its the microswitch or whatnot.

 

The microswitch if I recall is double-throw. Meaning there are 3 wires that go to it. 

 

If the microswitch gets bad to the point to where the normally closed position is open as well as normally open, it CAN cause the 1-wire only voltage situation which frys the SWIM and causes a shitload of other regulation problems. 

Edited by techknight
Link to post
Share on other sites

No, the wires are soldered together at the microswitch, any failure of the switch shouldn't impact this, the cables remain shorted. 

 

They both give 6.5V from the lead acid battery OR the 9V battery when flipping the switch. The 9V voltage is dropped by two diodes on the wire.

Edited by Mc128k
Link to post
Share on other sites

Weird, I thought I had the first version. As you can see here, the two wires on the right are soldered together and they go directly to the board. I presume that if you had them separated there could be issues when the main battery was connected without a backup battery (the frying you were talking about), so they had them joined while keeping a hot wire and a smaller one. Just a thought.

post-6801-0-73429200-1493472846_thumb.jpg

 

This is the rebuilt cable, as before both wires are soldered at the switch.

post-6801-0-82319400-1493472920_thumb.jpg

Link to post
Share on other sites

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.

Link to post
Share on other sites
  • 3 years later...

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

 

IMG_7883.JPG

Edited by Raoul
typo
Link to post
Share on other sites

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.

Link to post
Share on other sites
19 hours ago, Raoul said:

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. 

Edited by techknight
Link to post
Share on other sites
2 hours ago, glay78 said:


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. 

Edited by techknight
Link to post
Share on other sites
2 hours ago, techknight said:

 

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.

Link to post
Share on other sites
2 hours ago, glay78 said:


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. 

Edited by techknight
Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...

×
×
  • Create New...