Looks like I am going to be placing an order from digikey for some of these caps, I ran out of stock on a couple of them. Weeee......
Anyway, as a sidenote, i can discuss a little bit about the circuit design of my board. not every board is the same, some of them have integrated power supply hybrid IC, mine does not.
It has 2 DC-DC circuits onboard, both of them Linear Technologies branded parts. LT1054CS, and LT1070C
the LT1070C appears to the 5V regulator circuit to power all the logic circuits. Has a rather large inductor. It also has a wide range of input voltages, up to 60v. But when its configured for 5V out, it has a power handling capacity of 10amps in its output. Of course, thats heatsinked and everything, plus at about 60 to 80% efficiency, you would need at least 15 or 20 amps input. lol.
Anyway, since its not heatsinked, its probably setup to deliver around an amp or two on 5V. there are alot of 5V logic circuits including the drives as well, so you need something beefy to supply 5V.
On the other hand, the LT1054CS circuit has a maximum voltage input of 15V, so that pretty much limits the portables power input handling at tops 15V. since this is a switched-capacitor based circuit, I am assuming this supplies 3.3v for the logic circuits. Maybe 12v, but im not sure what part of the motherboard would need 12V except for the drives. Then again, i could have it all backwards and the LT1054 circuit supplies the 5V and the beefy 1070C circuit supplies the 12V. Not sure, will not know until i rebuild my board to get it to fire up. the caps are so bad they are leaking through the PCB Vias. But what I do know are the facts I had stated about power input handling capabilities and what circuits they are.
Ok, now for the part you might be interested in:
the DC jack appears to feed into an IRF9Z30 P type MOSFET Switch. the jack also has a sense switch when something is plugged in, will break from ground. This goes down to another linear technology part, the Sense OP-AMP. its output goes back to the 9Z30. From there it probably turns on the 9Z30 to allow current to come in.
The main power bus from the 9Z30 when switched on, goes directly into the battery via a fuse. So the circuits ARE interconnected via only a single IRF9Z30. Thats it. this 9Z30 is NOT heatsinked. So, if run entirely off the DC jack, you could in theory allow the 9Z30 to run hotter because its RDS(on) isnt very good. But really, thats it. Also it goes through a pico fuse of unknown type, so it could in theory pop the fuse, but i doubt it.
Once through the fuse, and into the 4pin battery jack, I dont know where it goes, it branches off into an internal power plane.
the DC jack/battery power bus also feeds into Q15, another IRF9Z30 that feeds voltage to both the LT1070C, and LT1054CS circuit, to supply it power. So this MOSFET serves as a power on/off switch to this regulators, this is controlled by Q204 SMD transistor.
Also, near the battery jack, with a heatsink is Q16, and L10 which form once another DC-DC converter circuit. Not sure of output voltage. Probably since it has a large heatsink, one of the voltages that requires a high load, such as the 12V for the drives. Battery output also goes to Q20, which serves to only switch on/off the LCD display.
From looking at this, it seems the DC jack keeps the system hot all the time until the charge monitor cuts off the 9Z30 so the battery will discharge to the point where the DC jack cuts in again. A form of trickle-charging.
So there you go, To enable a portable to run without the battery safely, all you need to do is short the source and drain on Q1, IRF9Z30 at the DC jack. This will interconnect the DC jack to the same bus as the battery. To feel safer, you could remove Q1 entirely and do the same. Short Source and Drain. Reason i say this, if Q1 ever shorts internally, itll short Drain and Source, AND.. Gate together which will blow the LT op-amp. and its game over.