You should get an POST card. Preferably the one with more components. There are some post on here about POST cards, although I don't remember them.

I'd look at the power supply and just run it with basic load (suitable hard disk for reference load perhaps, e.g. nothing connected to PSU except a dummy load for (usually) +5V to get voltage references right)

If that is ok, look for shorts on the motherboard - remove all unneeded loads, video card, ram etc. to check basic functionality.
e.g. a bios beep would only work when the cpu has test code to run so u need that - bad voltage regulators for cpu perhaps can be a problem. You could have a stuck reset signal keeping the cpu from doing anything useful. But you usually need some measuring tools.

I have a POST diagnostics card on the way as well as a little PSU tester that came with it.

In the meantime, I looked and saw a slightly bulging capacitor near the CPU. I noticed it a while back when I acquired the PC but it still worked fine. I desoldered it, hooked it up to my ESR meter, and it's definitely bad. I have a replacement on the way. I'll solder that in and let you guys know the results when I can test everything.

Syntho wrote on 2024-06-06, 15:42:

I have a POST diagnostics card on the way as well as a little PSU tester that came with it.

In the meantime, I looked and saw a slightly bulging capacitor near the CPU. I noticed it a while back when I acquired the PC but it still worked fine. I desoldered it, hooked it up to my ESR meter, and it's definitely bad. I have a replacement on the way. I'll solder that in and let you guys know the results when I can test everything.

Mind posting pics of the POST card?

edit: double post somehow

The first commandment of troubleshooting: Though shalt check voltages. (including voltage at the cpu socket)
After that, check the reset line.
After that, check the clock.
After that, check if the cpu is actually executing code

if all that is good, then you can start worrying about eliminating things like ram/cache/whatever you can unplug.

Syntho wrote on 2024-06-06, 15:42:

I have a POST diagnostics card on the way as well as a little PSU tester that came with it.

In the meantime, I looked and saw a slightly bulging capacitor near the CPU. I noticed it a while back when I acquired the PC but it still worked fine. I desoldered it, hooked it up to my ESR meter, and it's definitely bad. I have a replacement on the way. I'll solder that in and let you guys know the results when I can test everything.

i have a similar situation - a nice p4 system that i haven't run for a long time, ran it and:

first time started but screen was minimal res, seemed strange so i set in windows and then it crashed
restarted with endless beeps (usually memory or vid prob) and blank screen
re-seated components and restarted thinking the agp may not be seated properly - no beeps and no video, tried same with cell battery out and onboard vga - same result
minimised all - no ram, no cards, no disks, got three beeps (usually ram prob) and no screen
added one ram and back to no beeps and no screen

and then i noticed a very slightly bulged cap, so it might be that. the fact that the pc started but with problems, then crashed, then beeped then went completely silent suggests something long those lines. shame. now to weigh up time spend trying to solve against, well, not solving it

I've got a few tools here and there like a multimeter, oscilloscope, soldering iron etc, but I've never worked on or diagnosed a PC before. Is there a little tutorial somewhere that can guide me along for checking those things? I'll have the POST diag card and the new cap later today, so I'll update the thread when I get that done.

In the case of failed capacitors, unless there are some obviously exploded tantalum ones near the bus slots, the ones you are looking for are barrel shaped metal cans.

You want to check them for orange or brown "Goo" around the top of the vent, on the legs, underneath the can, OR-- for peaked, bulged tops near the little creases in the metal up there. Those are all very clear signs that the capacitor has failed.

Signs of failed capacitors in terms of a working system, are things like spurrious reboots, random but persistent bluescreens/lockups, etc.

I replaced the cap. Didn't progress any further. Still no BEEP and not POST'ing. So I put in my POST diag card. It only gives me dashes on the error display, which I read somewhere else means that it can't even get to the point that enough code is run to give me a code on the POST card.

When I took out the CPU in this machine, it had multiple broken pins. I think that CPU was just abused a little by whoever had it before I did. I put in a brand new P133 CPU but it's still giving me the same issue. And before I put it in, I went in there with non-residue contact cleaner and compressed air and blew out the socket very well. I'm thinking maybe something is wrong with the socket or something.

You guys have any more ideas?

Can you post specs of that pc? And pictures of the board would be very nice too.

I'll take a pic and post tomorrow when I'm back home. Something I forgot to mention is that the POST card didn't have its 3.3v LED coming on. It had +12, -12 and +5 illuminated. I wonder if that had something to do with it.

You can see the card here: https://www.amazon.com/dp/B072QSQQKT?psc=1&re … product_details

And the motherboard here: https://theretroweb.com/motherboards/s/azza-5is

Syntho wrote on 2024-06-08, 23:23:

I'll take a pic and post tomorrow when I'm back home. Something I forgot to mention is that the POST card didn't have its 3.3v LED coming on. It had +12, -12 and +5 illuminated. I wonder if that had something to do with it.

You can see the card here: https://www.amazon.com/dp/B072QSQQKT?psc=1&re … product_details

And the motherboard here: https://theretroweb.com/motherboards/s/azza-5is

Those cards will light up for a WIDE voltage range. You need to check the voltages with a meter.

I'll be getting onto that in a few here. I wonder if the 3.3v LED not coming on is what the issue is. Does anyone know what the 3.3v rail feeds?

As I remember BuB on yt done a video about slot 1 ASUS boards, which most of them had missing 3.3v. Turns out it was a de soldered mosfet near cpu slot on all of them.

CPU I/O for instance. Probably feeds some regulator for the lower Core voltages too.

https://cdn.preterhuman.net/texts/computing/i … 0Guidelines.pdf

Ok, according to this:

There is no actual 3.3v rail. I tested the P8 and P9 connectors and both were as they should be.

On old PC:s the +3.3V is generated by voltage regulators on the motherboard, usually close to the CPU.
Most chips were +5V back then, and I guess not much else used +3.3V; Super I/O chips I think did.

Syntho wrote on 2024-06-09, 16:11:

Ok, according to this: […]
Show full quote

Ok, according to this:

There is no actual 3.3v rail. I tested the P8 and P9 connectors and both were as they should be.

You're right. I've got 2 similar PCI/ISA post cards and one of them won't work in 5V-only PCI slots (nor ISA...). Have you...

• Measured the VRM output? If your board has the VRM slot it will surely have 2-4 jumpers, you can get the CPU voltage from any of those. Otherwise it'll be in one of the leads of the transistor with a heatsink just next to the battery
• Verified the BIOS chip? If you have access to a programmer, try reading the BIOS chip to see if it reads something or garbage.
• Cleaned the cpu and bios sockets with IPA or contact cleaner?