Doesn't the power LED also blink with a dead or ejected battery? Or am I thinking of a different laptop. I think my battery still holds a charge.

The battery on mine held/holds a charge, but with the power board dead you get no indicators at all.

Thermalwrong wrote on 2025-01-23, 20:16:

Watching the bench psu when I put this one up to 19v, the power LEDs on the laptop do not light and it does not respond to the p […]
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Watching the bench psu when I put this one up to 19v, the power LEDs on the laptop do not light and it does not respond to the power button. Very low current consumption.
If a CMOS battery is fitted it will remember this power fault state until the CMOS battery is removed, so this laptop no longer has any RTC battery since the fault state is easy to trigger and pulling out the battery every time is a nuisance.
The laptop is completely non-functional when used with its original power brick.

Strangely I found that when I reduced the voltage to 18.4v the laptop would not go into that power fault state and would run.

I've just ordered an adjustable bench psu for myself so that I can verify if the above is the same with all three power boards that I have in my possession. If that is the case then perhaps we can start to track down the underlying component fault.

Just for kicks I re-assembled the 807K (the one which was delivered working, and from which I took the working power board) and it, of course, is also now dead. It will be really interesting if I can verify whether any/all of the power boards actually fall in to the same category as yours; faulty at 19.5v, but live at a lower voltage.

megatron-uk wrote on 2025-01-24, 07:34:

The battery on mine held/holds a charge, but with the power board dead you get no indicators at all.

I meant with a working laptop. I know that's impossible at this point.

I really love these laptops but idk what the heck is wrong with the power board.

Thermalwrong wrote on 2025-01-23, 20:16:

Watching the bench psu when I put this one up to 19v, the power LEDs on the laptop do not light and it does not respond to the p […]
Show full quote

Watching the bench psu when I put this one up to 19v, the power LEDs on the laptop do not light and it does not respond to the power button. Very low current consumption.
If a CMOS battery is fitted it will remember this power fault state until the CMOS battery is removed, so this laptop no longer has any RTC battery since the fault state is easy to trigger and pulling out the battery every time is a nuisance.
The laptop is completely non-functional when used with its original power brick.

Strangely I found that when I reduced the voltage to 18.4v the laptop would not go into that power fault state and would run.

Bench power supply arrived this morning.

- I have tested all three power boards (one from the 809K which was bought non-working, one from the 807K which *was* working for 2 days, and one spare bought in unknown condition)
- Both laptops
- Voltages from 12v up to 20v DC

No change in behaviour. No visible draw on the bench supply (but it only shows a single decimal, so if it were lower than 00.1W or 00.1A it wouldn't register).

I'm not sure there is anything more I can do. The whole lot is now just a big pile of junk parts. I can keep the MMC-2 modules and RAM, but that's about it.

May as well hang onto the power boards in case they can be fixed. Can you find any replacements for the ICs?

I think that's a pretty sensible idea. My next task will be identifying the IC's (some of them are tiny, and my middle-aged eyes not so great any more!) and seeing if we can work out their function.

Perhaps there's something in the list that will immediately jump out as being a possible issue.

If anyone can help identify the IC's from the markings it could potentially help identify a cure for these faulty power control boards:

So far I have the following IC's listed:

Part Number(s) / Quantity / Pins / Manufacturer / Description
355A / 2x / 3 / ? / MOSFET
A00B / 3x / 5 / ? / ?
LT 1621 / 1x / 16 / Linear Technology / Rail-to-rail current sense amplifier
LT 1435A / 1x / 16 / Linear Technology / Synchronous step-down switching regulator controller
I?R 024H 4U3E f7413 / 2x / 8 / ? / ?
E2LD / 1x / 5 / ? / ?
4925 ?EUA W048 / 2x / 8 / ? / ?
?415A T07BAN / 1x / 8 / ? / Power control transistor
??? / 2x / 8 / ? / Tiny: 2.5-3mm wide. Almost impossible to read markings.

It would be fabulous if this turns out to be as simple as one of the little transistors.

megatron-uk wrote on 2025-01-28, 10:42:

Bench power supply arrived this morning. […]
Show full quote

Thermalwrong wrote on 2025-01-23, 20:16:

Watching the bench psu when I put this one up to 19v, the power LEDs on the laptop do not light and it does not respond to the p […]
Show full quote

Watching the bench psu when I put this one up to 19v, the power LEDs on the laptop do not light and it does not respond to the power button. Very low current consumption.
If a CMOS battery is fitted it will remember this power fault state until the CMOS battery is removed, so this laptop no longer has any RTC battery since the fault state is easy to trigger and pulling out the battery every time is a nuisance.
The laptop is completely non-functional when used with its original power brick.

Strangely I found that when I reduced the voltage to 18.4v the laptop would not go into that power fault state and would run.

Bench power supply arrived this morning.

- I have tested all three power boards (one from the 809K which was bought non-working, one from the 807K which *was* working for 2 days, and one spare bought in unknown condition)
- Both laptops
- Voltages from 12v up to 20v DC

No change in behaviour. No visible draw on the bench supply (but it only shows a single decimal, so if it were lower than 00.1W or 00.1A it wouldn't register).

I'm not sure there is anything more I can do. The whole lot is now just a big pile of junk parts. I can keep the MMC-2 modules and RAM, but that's about it.

Make sure there's no CMOS battery or main battery fitted when doing these tests. because if those are fitted the laptop will stay locked in the no-power state. Ideally also turn the output off/on when changing voltages.

What's the current consumption showing as? Just testing my dodgy one out and when it's got too high voltage the current consumption briefly goes up to 0.03 amps then drops to 0.00a. If I change the voltage down to the acceptable range with the psu output enabled, the laptop remains in the no-power state.

When the laptop is powered with 18.4v (the highest it will accept, 18.5v causes the no-power state) it draws 0.016a. None of the LEDs are lit until I press the power button then the laptop shows its LEDs and starts up after a few seconds.

All my CMOS batteries are removed and no main battery is installed.

Unfortunately the bench supply only provides one decimal place of accuracy, i.e; 1.2a, so the lowest I can visualise is 100mA, and am unable to see if there is as small a current draw as you describe.

No lights and no response to the power button, regardless of voltage in my case.

I can try setting the lower voltage without adjusting it down from standard whilst plugged in. I didn't try that explicitly.

Actually it's 2dp, so 0.00a, it's the power rating that only shows 1dp; 0.0w.

No, no difference. I started the PSU up at 17v and there is no draw at all (at least nothing that shows as much as 0.01a).

No difference in behaviour with the LEDs or power button.

Input voltage is still present on that pad on the power board I identified earlier in the thread, so it's still getting from the DC jack and motherboard to the sub board.

It's got to be one of these power control IC's. But (a) I don't know where to start, and (b) some of them are way beyond my eyesight and soldering ability 🤣!

I can solder these but I don't know if replacement parts are available, which part is bad, or how to test any of them.