I bought an used PC, and it only gives black screen

[Martin Howe]

Professional PAT (electrical safety) tester and computer refurb guy here - electric shocks from the casing may be small now, but could grow; if the earthing conductor in your power plug/lead is faulty, it could literally kill you if the PSU degrades further. For the love of god, get that computer PAT tested before doing anything else with it when powered. It could not only save you buying another motherboard, it could save your life. Though by the sound of it, your PSU is screwed  anyway.

[Murdoch]

11 hours ago, Martin Howe said:

Though by the sound of it, your PSU is screwed  anyway.

 

Unquestionably. I've never been shocked by a Psu but a local school bought two desktops to me back in the day where if you tapped the case it would reboot. Replacing the PSUs solved the problem. One customer's case got so badly tarnished by moisture that it eventually caused the PSU to short out and fry the board cause it couldn't earth properly. 

[dasho]

I don't know if I would throw good money after bad in this case; might be worth saving up for and building out something new altogether.

[Major Arlene]

13 minutes ago, dasho said:

I don't know if I would throw good money after bad in this case; might be worth saving up for and building out something new altogether.

I'd have to echo this sentiment, a bit more labor intensive but at this point just as much effort has been put in to diagnose the thing.

Edited May 19, 2024 by Major Arlene

[Rykzeon]

On 5/18/2024 at 5:56 AM, TheMagicMushroomMan said:

Have you tried booting with a single RAM slot and then moving it to another slot? I had a strange issue where one of my RAM slots went bad and my PC wouldn't reach POST with anything in that slot. Is your heatsink secured properly?

 

 

On 5/18/2024 at 9:58 AM, Murdoch said:

As jello said shocking isn't good and earthing problems, while rare, can cause issues. Worst case scenario its fried the board. I've seen that happen. It's a pretty old machine so don't spend too much money on it trying to get it working. Find a known working secondhand psu if possible,  and if it still doesn't work try the following. Diagnosing blind is basically impossible and all anyone can offer is educated guesses. It could be the CPU, RAM, motherboard or video card.

 

If it does have integrated graphics, take the card out. Simplify and eliminate as many variables as possible. You've already tried alternating the RAM. Both could be bad but that's statistically improbable. Take the battery, RAM and Cpu out. Might as well clean the thermal grease off the CPU and heatsink and put fresh grease on. Reseat the CPU, heatsink, battery, and one stick of RAM. If it doesn't work try the other. If that doesn't work, try each piece of RAM again but in the other slot as slot failure isn't uncommon on older boards. If it still fails, the board or CPU is probably gone and given the age, repair is likely not going to practical and/or cost effective 

I did alternate the RAMs. Disconnecting or not fully attach the heatsink only makes the computer shut down after few minutes.

It seems it does has integrated graphics, as I can't see any "F" in the processor. The GPU also warms when attached.

 

On 5/18/2024 at 7:44 AM, Jello said:

"I also get a little shock from the casing when trying to unscrew the motherboard. Not sure if the casing comes contact into my old pc or nope."

"The CPU casing has shocks when connected. I checked the PSU fan and it is spinning when the PC turned on. The motherboard LED also lit when it connected to a power source"

 

Is this just a language barrier where "shock" means that the components are trying to start when you connect them to an electric receptacle, or are you literally feeling electricity discharge from the case into your body when you touch the case? Because you should never be getting shocked by the case of your PC, and if you are, there's a severe grounding issue, and it should probably be chalked up as a lost cause. It's possible it's an issue with the PSU, possibly a faulty capacitor, but don't dink around inside the PSU.

 

So, have you tried replacing the PSU? Because that's where I would look first based on what you've said, but if it's having noticeable electric discharges just by touching the case, it's probably fried multiple components everywhere, and it's beyond repair.

I touched the case and it gives me electric shock. I guess I'll check the PSU then, because I haven't checked it because I've seen a PSU that gives warning to not even touch it when I was kid.
 

On 5/18/2024 at 3:03 AM, dasho said:

Besides the fact that it sounds like there may be a grounding issue, if you can at least get to where it beeps again you can typically look up the beep codes for the motherboard in question to maybe have a clue as to a potential problem. The "beep code" refers to the number and length of beeps you are hearing.

It only beeps if I unattach both RAMs so far.

 

[Jello]

2 hours ago, Rykzeon said:

I touched the case and it gives me electric shock. I guess I'll check the PSU then, because I haven't checked it because I've seen a PSU that gives warning to not even touch it when I was kid.

They're fine to touch and handle, otherwise people wouldn't be able to build their own PC's or replace them, just don't open one up and start messing around inside it. They have no user serviceable parts, and there is a risk of severe electric shock if you start messing around inside them. Just unplug the PSU from the wall and hold the power button down for a few seconds to discharge any electricity that's being stored in the PSU before you start disconnecting internal cables or removing it.

 

Oh, and whatever you do, listen to Murdoch when he tells you things about fixing computers. He kind of knows what he's talking about, he kind of makes money doing it.

Edited May 20, 2024 by Jello

[Murdoch]

2 hours ago, Rykzeon said:

Disconnecting or not fully attach the heatsink only makes the computer shut down after few minutes.

 

You misunderstand. You should never do that as by the time a computer shuts down to protect itself due to overheating, potentially some damage has already been done. Said damage may not be fatal, but it should still be avoided.

 

My advice was motivated purely as to giving the board as clean a state as possible. Sometimes on old machines, BIOS memory can get corrupted which can cause boot issues, hence the advice to remove the battery. Static build up and corrosion can also cause issues, and sometimes simply reseating everything can get it booting again. It hasn't happened for a while, but sometimes people would call me saying when they powered up their desktop tower nothing would come up on the screen. The first thing I would tell them to do is shut it down and disconnect it from the power for a bit, plug it back in, then call me back if it still wasn't working. Roughly half the time, I wouldn't hear back. What I told you was basically the next evolution of that idea. Disconnect everything, then reseat it. I definitely did not mean you should boot it without the heatsink.

 

1 hour ago, Jello said:

He kind of knows what he's talking about, he kind of makes money doing it.

 

Yes, I am a professional. Kind of :P

Edited May 20, 2024 by Murdoch

[Redneckerz]

Atleast make yourself grounded if you are going to mess with a PSU.

 

Since im like Murdoch and do this kind of thing somewhat for a living: Just get another one. Yes, i know, money and all, but a grey box PC that literally stings you ain't a great grey box PC.