Question Dell Inspiron 5100 (2003) with RAM issues (voltage, PSU suspect ??)

[13hm13]

Here's my device:
LAPTOP: Dell Inspiron 5100 (2003) 2.4Ghz p4, dual-boot: Windows XP pro, sp1 + LinuxMint ( LM 17.1 MATE ), with 128GB ssd, 512mb ddr sodimm.

The 5100 runs fine, even after 19 years of daily, gentle use, "always on", and on adapter power only.
HOWEVER, over the past 5-6 years there has been a restart-up issue (after power down or power loss --- I leave all my PCs/laps in daily use in ALWAYS-ON condition, even going months w/o re-boots, but the inevitable always happens) .
Seconds to few mins after pressing the power button to restart , the lap tries to get into BIOS, but the screen remains blank and laptop powers down automatically after 10 sec. Repeat power-button press a few secs to a few mins later. Same issue. HOWEVER: If I waited more than, say, 0.5 hrs to restart (like typical power blackout), start up NORMAL -- BIOS, Win startup, all NORMAL.
Looked into tho issue, and it was as I suspected, a memory module (RAM) issue. The short (10 sec) failed BIOS bootup I noted above does display a diagnostic LED fault code:
The Caps Lock flashes this code:
--------

Off

Flash

Off

The memory is believed to be good but it is about to be exercised (such as when shadowing the BIOS and when testing / zeroing all memory).

Reseat the memory module(s)

--------

https://www.dell.com/support/kbdoc/...-notebook-diagnostic-indicators#Prior_to_2006

HOWEVER, the lapse in time before the laptop re-starts normally has been getting longer (say 1 hr) .... up until a week ago when all I could get, even after hours of power-down, was the same flashing Caps Lock led.
I swapped memory modules and FINALLY got one (256 MB, lower than orig. 512MB) to work. But that 256 didn't want to start smoothly either (often with the same Caps Lock flash code). I have several other modules on hand. A 128MB works, but as far as I tested, nothing over 256.
It may be that the PSU circuits are getting old. Haven't opened up the 5100 yet (to look at the MBD), but I saw no electro caps from some online photos of the 5100 internals.

EDIT:
Whether re-boot attempts made from battery alone, or ac adapter (no battery) seems to make NO difference ... same issue.
May 2017, I replaced the orig. AC pwr adapter (20v, 4.5a) to a new one (19.5v, 4.7a) . I wonder if increasing the adapter voltage by 0.5v might now add enough juice to get higher-capacity memory modules t operate (or at lease make for smoother , more-reliable power-ups).

 

[Lutfij]

It's very likely that the power delivery components on your laptop's motherboard are giving way due to old age/wear and tear. Also, rams of that era aren't even supposed to be alive so if anything the ram sticks might even be the issue due to the flashing caps lock LED. You might want to note the sequence of the LED's flashing though, that does correspond to an error code.

 

[13hm13]

It's very likely that the power delivery components on your laptop's motherboard are giving way due to old age/wear and tear. Also, rams of that era aren't even supposed to be alive so if anything the ram sticks might even be the issue due to the flashing caps lock LED. You might want to note the sequence of the LED's flashing though, that does correspond to an error code.

Most of your reply is not helpful.
As I noted, I did install several other RAM sticks to test (see OP), many of them are new or very low hours.
About the LED code ... I provided a link in OP. Dell does not indicate anything beyond what's in that table.
One thing I forgot to mention is that this lap top has TWO sodimm slots, A and B (each 266Mhz). Now, however, only SLOT B now works. I do recall SLOT A used to work.