• Hello, Guest! Welcome back, and be sure to check out this post for more info about the recent service interruption and migration.

Mac Portable Hybrid: combine forces?

Siliconinsider

Well-known member
That running the Portable in the old, received wisdom (idiocy in this case) no battery/higher output AC Adapter state has killed so many Portables I'm wondering about that? @techknight what components would be at risk of being taken down in said catastrophic failure? IIRC Hybrid would be the primary point of failure?
The hybrid module pretty much deal will all the voltage rail generation on the motherboard, with power sources coming from both the power adapter, and the battery. It uses some external components, a couple MOSFETs that are around it, and a LT1070 to generate the +12V rail. 1989 vintage DC/DC converters and MOSFETs were in their infancy, today it really is no big deal so entirely bypassing the whole thing with a power supply system designed with reliable and easy to source components seems like a good idea.
 

mg.man

Well-known member
@Siliconinsider, I assume you spotted this...
It is already being worked on and basically functional
@androda has the lead here
Also... there was another recent thread...
 

mg.man

Well-known member
today it really is no big deal so entirely bypassing the whole thing with a power supply system designed with reliable and easy to source components seems like a good idea.
perhaps a small 'board that would 'solder in place of' the hybrid?
 

Siliconinsider

Well-known member
It is already being worked on and basically functional
@androda has the lead here
I do know, but it is a 1:1 replica of the original module using the same hard to source components and precision resistors... not to undermine the immense effort of the task, it seems the hybrid just generate +5V and -5V, as well as a couple control signal for the PMU.
 

Siliconinsider

Well-known member
ugg... sounds beyond the capabilities of mere mortals... will what you have in mind "fit" in a similar size footprint = my above question?
It could fit in 1/4th the footprint, so certainly in the volume of the module. It could also bypass some of the old power components and capacitors that are around the module.
 

mg.man

Well-known member
It could fit in 1/4th the footprint, so certainly in the volume of the module.
Sounds interesting... I'd certainly be willing to remove the Hybrid from one of my non-working 5120 'boards to serve as guinea pig. I'm planning on trying your 'direct' power technique first - not much to lose with the 'board I have in mind.
 

Siliconinsider

Well-known member
I have one here to work on. You can tie +5V to the heatsink of Q16 and ground to the battery ground. Make sure you have a regulated power supply, and set current limiting to make sure that nothing release the magic smoke. Note that this will power the entire +5V rail but not some other rails, especially the +12V which the hard drive and audio amp need.
 

mg.man

Well-known member
Make sure you have a regulated power supply
(y) I already use one for inputting 7.5V / 1.5a (max)... I'll just dial-down to 5V.

this will power the entire +5V rail but not some other rails
Noted, thanks! I'm mainly interested in seeing if there is life... atm, it just clicks when reset - but does seem to be trying to charge the battery. I've also tried with a full battery - power draw is lower, but still just the 'click' (pop on speaker) when reset. I really should get a 'scope or something - just not been willing to spend those $£€ yet...
 

Siliconinsider

Well-known member
Unplug the hard disk, and dial current down to 400-500mA. It should power when you press the keyboard and display the floppy icon.
Pretty much all the portables I have seen (well, 3 so far) have had supper finicky power supplies, but with the 5V hardwired like that it powers on rock solid. So it all points out to the hybrid and old DC/DC tech.
 

Siliconinsider

Well-known member
So I wend deep into the details on how voltages are generated and learned a few things.

- The main +5V is generated using a MOSFET and a feedback loop with an op amp to drive the gate with a PWM signal. This can go wrong and is the reason why I'm seeing the hiccups on the power supply. When this goes wrong, VBat or Vcharger are fed straight to the 5V rail, taking down chips that are connected there.

- There's another +5V rail for the hard drive, generated outside of the hybrid, but using the exact same circuit, with an op-amp and PWM. It also can fail in the same manner as above and bring VBat or Vcharger to the hard disk 5V rail.

- The battery and the charger are fed through the exact same path, so they are not treated differently. The charger circuit is very simple, Vcharger is simply connected straight to the battery to charge it, and the PMU monitors the voltage until it reaches full charges.

You can fully power your portable to test it using a regulated +5V source, able to supply about 2.5A peak when the hard drive start (700mA when hard drive is spinning, 400mA when computer is on and hard drive off).
1) Connect the 5V source to the heatsink of Q16, this bypass the hybrid regulator and feed 5V straight to the main 5V rail
2) Connect 5V to the tab of either Q14 or Q15 (they are in parallel), this will feed power to the LT1070, which in turn will generate the +12V rail for the hard disk drive and audio
3) Connect 5V to the heatsink of Q20, this bypass the external PWM regulator and feed 5V straight to the hard disk drive 5V rail.

When turning the power, the hard drive will spin as it is not longer controlled by the system. Then the system can be booted by pressing on the keyboard. When booted in the OS, some erratic messages about battery charge may appear as the hybrid is left floating and the PMU is not receiving correct readings.

IMG_2892.JPG
 

mg.man

Well-known member
Woo woo...

20220318_182113.jpg

...and, it even boots from my FloppyEMU

20220318_182215.jpg

This was with a single 5V feed to Q16. As expected, just after booting it complains about the Battery and goes to sleep. Still, great to see there is hope! Thanks @Siliconinsider for coming up with this. Looking forward to your continued investigations! :cool:
 

techknight

Well-known member
I do know, but it is a 1:1 replica of the original module using the same hard to source components and precision resistors... not to undermine the immense effort of the task, it seems the hybrid just generate +5V and -5V, as well as a couple control signal for the PMU.

The community is going to be divided in this way. youll have the people who want big patch wires running all over their boards for a "replacement redesign" and you are going to have people who want to keep things as original as they can, but also working.
 

techknight

Well-known member
So I wend deep into the details on how voltages are generated and learned a few things.

- The main +5V is generated using a MOSFET and a feedback loop with an op amp to drive the gate with a PWM signal. This can go wrong and is the reason why I'm seeing the hiccups on the power supply. When this goes wrong, VBat or Vcharger are fed straight to the 5V rail, taking down chips that are connected there.

The drive to the gate of that MOSFET is not PWM. That regulator is very much a linear series-pass setup. If there is anything other than a voltage there, then there is something very wrong, such as it has gone into an oscillation.
 

nottomhanks

Well-known member
I have a backlit portable that I restored about a year ago, but now I’m getting flickering backlight activity that coincides with RAM (MacEffects card) or Hard Drive activity. I’m wondering if the battery has gone bad or if there’s another power regulator problem. I had the display backlight board recapped as well.
 

LaPorta

Well-known member
The community is going to be divided in this way. youll have the people who want big patch wires running all over their boards for a "replacement redesign" and you are going to have people who want to keep things as original as they can, but also working.

I agree. My hybrid works just fine, and I would like to keep it that way. If I could replace components when they fail, I'd just replace them if they are able to be sourced. My goal is always to keep my machines as original as possible. Then there are others who would install a modern machine with an emulator in place of the entire old machine if they could. Everyone has a different goal.
 

Siliconinsider

Well-known member
No one is talking about running wires all over the board. The original portable power supply was not very well designed from the start, with instabilities that could send VBat straight to the +5V rail (especially with bad capacitors) and weak current handling which makes it impossible to run it without a charged battery.

The photo above just shows how you can power your portable with regulated +5V DC to test if it is working, bypassing the original power supply stages.
 
Top