Dell 5100 Inspiron won't re-power on for 20min

[13hm13]

I have a 2003 Dell Inspiron 5100 laptop -- used for company legacy apps. It's always on (and has been for 16 years!!). Pretty much trouble free. Except, over the past two years, in the rare case that it needed to be re-booted, I can't get it power on for about 20 min or so.
I press PWR button and the LEDs come on, and fan spins ... but screen remains black. Sometimes it shuts down automatically (after 10 sec or so) ... or I shut it down because fan spin is maxed.

It acts like a memory issue. But I have several new (spare) memory sticks ... same issue. A while back, I could get it to immediately re-power more frequently if I used 256MB instead of 512MB memory stick. Now, even the 256MB causes delay.

I was thinking dry electro caps. But I saw pics of the main board and I saw only few electro caps?

FYI: I do use a newer SSD in this Dell. I replaced the 16-yr-old Hitachi 40GB only a few weeks back (it still works perfectly!)
When the laptop is on, it works perfectly. No blue screens, no lock ups. It's a great computer except for the recent delay pwr-up issue.

[amyk]

There may be residual charge that's taking some time to dissipate because there's something preventing it from discharging the main power rails.

Try to find the schematic and debug from there.

[trevatxtal]

Have you checked the bios backup battery ?
Trev

[13hm13]

I haven't checked. But why would a weak battery cause the issue I noted?

[13hm13]

There may be residual charge that's taking some time to dissipate because there's something preventing it from discharging the main power rails.

Try to find the schematic and debug from there.

Haven't gone the schematic route.

Should've perhaps noted in OP ...  I have tried (multiple times), removing the battery (then reinserting) -- didn't work.
Removed memory (then reinserted) ... didn't work.

[coromonadalix]

Do you have thermal throttling / shutdown ?  stuck up cpu fan, to much dirt in it ??

[amyk]

Should've perhaps noted in OP ...  I have tried (multiple times), removing the battery (then reinserting) -- didn't work.
Removed memory (then reinserted) ... didn't work.

The schematic was pretty easy to find, but unfortunately lacks power sequencing diagrams. It's an older, simpler design, so should not be too hard to troubleshoot --- the overall power flow is shown on page 4. After removing battery and AC adapter, there will still be the RTC backup battery voltage but all the other rails should be dead. You can measure with a (high-impedance) multimeter to see which ones still have residual charge, and if you do find one, discharge it and see if it will then boot normally.

[13hm13]

Should've perhaps noted in OP ...  I have tried (multiple times), removing the battery (then reinserting) -- didn't work.
Removed memory (then reinserted) ... didn't work.

The schematic was pretty easy to find, but unfortunately lacks power sequencing diagrams. It's an older, simpler design, so should not be too hard to troubleshoot --- the overall power flow is shown on page 4. After removing battery and AC adapter, there will still be the RTC backup battery voltage but all the other rails should be dead. You can measure with a (high-impedance) multimeter to see which ones still have residual charge, and if you do find one, discharge it and see if it will then boot normally.

Thx for finding the schema!
Are there passive components that cause "sticky" charge (voltage) as they age or deteriorate? I always assume it was the opposite.

[MosherIV]

Hi. This might be 'known behaviour'!
I have a very old Dell Latitude laptop where the led/power switch pcb would develop a crack/dry joint which would stop it powering on. Symptom are screen light up, leds flash for a few second and then stops. By pressing somewhere on the top or bottom of the case you can get it to turn on.

One of my lap tops at work will not turn on if they have been discharged. It is a M6800 portablt workstation. It will just turn on the fan and it gets very hot.
I found that it needs to be unplugged for a few minutes, plug it back in and press and hold the power button until it turn on correctly.

Current Dell laptop have a tendancy to lock up in the sleep or suspend mode so that you cannot wake them. The batteries are non removable, so you cannot reset them by removing the battery. You have to hold the powrr button for 30 second to force the laptop off.

There may be other known things like this.

Hope this helps

[13hm13]

One of my lap tops at work will not turn on if they have been discharged. It is a M6800 portablt workstation. It will just turn on the fan and it gets very hot.

Yes, the fan spins crazy fast. But...

I found that it needs to be unplugged for a few minutes, plug it back in and press and hold the power button until it turn on correctly.

Most of the time, when this happens, the Dell powers off automatically after a few secs.
I've tried removing the memory stick altogether and same issue (dark screen; crazy fan spin; auto power off). (And recall what I noted earlier about better results with 256MB than 512MB).
If I keep the pwr button depressed (as you noted), it stays in that fast-fan condition until I release pwr button.
Also, when the issue is present, the Keyboard Status LEDs do some coded blinking.