I'll try to test the PSU with my 486's motherboard (I'll just plug it in its AT power socket and turn it on), if it turns on, then the PSU is fine and the issue must be the CMOS/RTC.
If it won't power on the 486 motherboard, then it's either the PSU dead or not powerful enough for a 486 motherboard (which I doubt it's possible)

These two are the only AT motherboards I currently have, every other motherboard I own is ATX.

Elia1995 wrote:

I'll try to test the PSU with my 486's motherboard (I'll just plug it in its AT power socket and turn it on), if it turns on, then the PSU is fine and the issue must be the CMOS/RTC.
If it won't power on the 486 motherboard, then it's either the PSU dead or not powerful enough for a 486 motherboard (which I doubt it's possible)

These two are the only AT motherboards I currently have, every other motherboard I own is ATX.

konc wrote:

candle_86 wrote:

unplug 386 from psu and then press the power button and find out if that psu works

Did you do what candle_86 suggested? Does the PSU work with everything unplugged or still it "stops completely"?

I haven't had a chance to test it yet.

I brought this PC here home today, I'll cable it and make a quick video of it to show what happens when I try to power it on and I'll get some macros on the motherboard chips and parts tomorrow, guys !!!

Ok I just tested the PC.
It actually turns on and stays on, but I get no video

Here, I just made this video: https://youtu.be/S6SOhZIA0BA

And here are some photos of the board with macros on almost every chip I could see:

This is the whole board, "what you see" when you open the PC:

That's the right side of the motherboard, right below the SIMMs; the "Intel" chip I guess is the 386 CPU... soldered in the board instead of being "removable" like my 486.

There's a close-up of the CPU, as you can read it's a 80386SX-16... it'd be a shame to waste...

I have no idea what goes in this socket, it has always been empty, maybe it's a slot for a second CPU or something, I dunno.

That's the "mod" my father tried to solve the issue, he soldered an AA battery with two wires and plugged it in a CN1 pin-thing... but it didn't solve anything at all.

This is an "ADV476KN66E" chip (I have no idea what it is, actually... I just typed what's written on it 🤣)

I have no idea what this WDC big chip is, might be the "graphics card".

Then there's also this big "EPSON" chip here...

3 SIMMs, that's the maximum this board is capable of... and a perfect healthy cap right in front of them (it's annoying, I always have to bent it to remove and insert the first SIMM, that's stupid)

I have no idea what this is. That marker "4" isn't mine... I don't even write the "4" that way...

The two parts of the board are kept together with these two white things:

Here's the AT PSU's sticker with all of its details:

Here's the back panel, very simple: AC plug, VGA, Keyboard, Mouse, Serial and Parallel

AND YES, IT ACTUALLY HAS A 15-PIN VGA AND NOT 14-PIN LIKE THE 486 !!! Even though it's older... WTF !!!

This is the front panel, in case someone recognizes this PC:

I didn't see the "Dallas RTC" chip anywhere...

Well, as I expected, that's a very nice proprietary Epson motherboard that likely needs to be configured in a somewhat unusual manner. The empty socket is for a co-processor. See if you can find any kind of type indication and try tracking down the manual. It probably floats around on the web somewhere.

A picture of the entire front would help, as would sharp pictures of any labels on the in- and outside (can't read the one on the rear right now).

Is that a PS/2 mouse connector next to the equally PS/2 keyboard connector? PS/2 on a 386 is pretty rare. Why is there an adapter between the keyboard cable and keyboard plug despite both seeming to be PS/2? Maybe the Epson has a non-standard pin configuration for the keyboard connector?

Also, what kind of monitor is connected to it? If the monitor doesn't support the video output it's possible you simply don't get any image.

Both mouse and keyboard are PS/2 on the board, I'm using an AT to PS/2 adapter for my keyboard because the keyboard has an AT plug.

This is the monitor I've always used with this PC, however its cable is built-in and has only 14-pins while the PC has a 15-pin VGA, but as I just said, I've always used this very monitor with this PC and has always worked.

I'm seeing hour photos on my phone but I think you are using EDO ram. If it is the case the machine won't work. 386 needs Fast Page Mode ram.

It has some onboard RAM, you can try without any SIMMs inserted.

What do I do with that AA battery ?
And how can I tell the difference between EDO and Fast Page SIMMs ?

Elia1995 wrote:

What do I do with that AA battery ?
And how can I tell the difference between EDO and Fast Page SIMMs ?

First off, it's not an AA battery, stop calling that before I blow a gasket.
Sorry to get annoyed, but that's a 3.6v Nickel Cadmium battery with an unusual form factor. It's the same type of battery as the ones everybody wants to snap off the board due to leakage. Don't be worried, if it's new and outside of the board, it will be decades until anything is the matter, but the originals have been in there for decades.

Now that that is over, I heavily doubt that a 386 board is using EDO memory as the first chipset to even support EDO didn't come around until the 486 era.

If you seriously want to check, look at the model codes on the individual chips, and try to find a datasheet. It will label right on there if it's supported or not.

If you think it's the RTC and that injecting a battery by de-potting the chip and soldering directly didn't work (Probably should have), you can remove the RTC, ADD A SOCKET, and replace it with an identical chip (They are available for pennies around the world.)

As was said, OEM gear especially around the 386 world was made for you to plug it into the wall, add a keyboard and monitor, and that's about it. They were configured by people with service manuals the size of dictionaries, and they are not fun to configure.

But who was stopped by that amirite?? My suggestion is to find a service manual for that model and go through the troubleshooting steps for it. They often have beep/blink codes or other forms of communicating that this is not how it's supposed to be.

I just removed all the SIMMs, but nothing changed at all..

Elia1995 wrote:

I just removed all the SIMMs, but nothing changed at all..

Several people including myself in this thread have made various suggestions about what you could do to discover more information on this system (or test the power supply), yet instead of trying to find more information or providing better pictures so we can find more information you keep not doing those things, and it's starting to get pretty tiring. To be honest (sorry to be blunt), it sounds like you're in over your head and don't really know what you're doing. So either start searching the web to find more information, reading up a bit to figure out what you have, and help us to give you proper help (e.g. by helping us to figure out the system's type number), or find someone who can help you in person, before you inadvertently butcher this rather interesting machine... 😒

Someone asked for a full picture of the front cover:

On the back it's just a bunch of "caution" stuff

I can't find the motherboard model number, I'm looking through all the pictures more carefully now, if I find it I'll add it here.

These might be interesting (found on various parts of the mobo):

I am trying to track down the model on Google to find the manual, but I can't find it at all, even if I search "Epson El Plus 386 PC" I don't find this one.

TBH, we can't help you further. Unless someone else has something to pitch in, you need to track down a service manual.

I can't find the model of the PC, I'm even looking on ManualsLib under the Epson > Desktop computers, one by one, but no way I can tell which is the right one since there aren't photos of the PC but just drawings (as like taking pictures of the PC motherboard and printing them in the manual was that much effort 20 years ago for a rich company like Epson)

Elia1995 wrote:

I can't find the model of the PC, I'm even looking on ManualsLib under the Epson > Desktop computers, one by one, but no way I can tell which is the right one since there aren't photos of the PC but just drawings (as like taking pictures of the PC motherboard and printing them in the manual was that much effort 20 years ago for a rich company like Epson)

Sorry.

I found some pictures of an Epson EL Plus at Museo del computer
Couldn't find a service manual there though.

Here's the Internet archive page of the old Epson US support website: https://web-beta.archive.org/web/*/http://www … p?UseCookie=yes.

Elia1995 wrote:

I can't find the model of the PC, I'm even looking on ManualsLib under the Epson > Desktop computers, one by one, but no way I can tell which is the right one since there aren't photos of the PC but just drawings (as like taking pictures of the PC motherboard and printing them in the manual was that much effort 20 years ago for a rich company like Epson)

That's pretty common for a lot of companies, even nowadays. Photos aren't exactly compatible with the often quite cheap printing methods used for manuals (besides, schematic drawings are easier to modify... 😉 ). So you'll have to do with the schematics, should not be particularly hard to compare the rear of your system with the schematics in each manual, just time-consuming (but that's how things are when researching old machines).

yawetaG wrote:

Here's the Internet archive page of the old Epson US support website: https://web-beta.archive.org/web/*/http://www … p?UseCookie=yes.

Elia1995 wrote:

I can't find the model of the PC, I'm even looking on ManualsLib under the Epson > Desktop computers, one by one, but no way I can tell which is the right one since there aren't photos of the PC but just drawings (as like taking pictures of the PC motherboard and printing them in the manual was that much effort 20 years ago for a rich company like Epson)

That's pretty common for a lot of companies, even nowadays. Photos aren't exactly compatible with the often quite cheap printing methods used for manuals (besides, schematic drawings are easier to modify... 😉 ). So you'll have to do with the schematics, should not be particularly hard to compare the rear of your system with the schematics in each manual, just time-consuming (but that's how things are when researching old machines).

whenever I try to get to the documentation pages :\

http://www.manualsworld.it/manual/171049/epson/386sx-16-plus This is the closest manual I just found, still not sure if it's the same model, but I can't find anything else than those "EQUITY" series...

And it says dumb/obvious things about the monitor issues... as I expected.