Compaq Portable III Errors: Bad Power Supply?

[T-Squared]

After I got my Glitchworks RTC/CMOS power module, and soldered it to the chip, I started having "201-Memory Error"s pop up (unrelated to the CMOS chip), and the system seemed to hang (with a blank black screen, no orange display) on cold restarts. I figured they were legitimate at first, as indeed one of the connectors was not pushed in all the way. (The board that connects the memory expansion and modem to the motherboard)

I kept getting them, so I cleaned the offending connector with Deoxit. Still no change. So I took out the memory expansion. It cleared the bit pattern indicators (to show what bit was not working), but I still kept getting errors, and at least once, the diagnostics picked up a "System Board Failure" error, so I used Deoxit on the base memory and slots. However, I kept getting the error even afterwards, but then it started bootlooping, with a different hexadecimal number every time after the bit indicators. (i.e. BD00, 4676, 8000) I probably should have seen this coming, because I had a similar error (Disk Controller Failure) when I refurbished the system back in 2018. It mysteriously cleared itself when I started it up a few days ago to test, since the

Everything seems ok, but after faffing about with that, I have come to the conclusion that the capacitors in the power supply have finally fallen out of spec. (Even though a lot of people might say replacing the capacitors is either a fluke or stereotypical snake oil at best.)

EDIT: Checking them this morning, I found that the capacitors have seemingly fallen out of spec. (a 470uf cap read in the 500uf range, and a 1700uf cap read in the 2200uf range!)

I'll be getting new caps from Mouser.

 

[T-Squared]

Ok, good and bad news.

Good news:
The recap was successful.

Bad news:
I kept getting memory errors after that, especially when it had warmed up. Deoxit seemed to make it worse, somehow.

Good news: I found that moving the expanded memory sticks made a difference. (I'm thinking that the "bit indicators" were actually RAM slot indicators, telling what affected RAM was in what slot.)

Bad news: I got graphical and text glitches with the swapped sticks. Even got a really bad memory error.

Worse news: The board that connects to both the modem and expanded memory card has a busted motherboard connector. (One pin kept getting bent wildly out of shape, and I didn't want to risk breaking it by stressing the bend. The connector on the main motherboard is just fine, though)

Better news: I was able to desolder the connector and clean the holes with no real problem.

Not-so-good news: I know how many holes and pins (2 rows of 96 holes, but with 84 pins loaded) are on the connector, but I don't know what brand it is or what it's called. It looks like a micro version of a floppy disk or IDE drive connector. (It's even got a plastic shroud around it like one.)

Okay news: The system still works with 640k.

Not-so-okay news: I need a new 1225 battery for my RTC power module, because the chip doesn't seem to be powered with the provided battery, even though it shows 3.2v.

 

[T-Squared]

Oh yes, I almost forgot to mention, I get static from the internal speaker for some reason too, with the expanded memory.

 

[CedsRepairs]

FYI a 470uF capacitor indicating 500 is not really from out of range
You can at least expect 20% variation, and sometimes even more especially in those vintage computers.

Also bear in mind these are used for filtering, not for making a digital clock so their precise value doesn't matter much, as long as well they filter DC.

What important is however important (if you replace capacitors in a power stage) is to replace low impedance ones with other, low impedance ones.
(Usually these are only used in the DC-DC converters stages, nowhere else, as they cost more)

Example of such vintage low-Z are Nippon ChemiCon SXC range.

All the rest, you can use the cheapest capacitors you'll find (rubycon, etc) - but for power stage, it's worth it imho to use like panasonic in the FR/FM range (for example, as I only know panasonic)