stanwebber wrote on 2023-09-12, 06:47:

capacitor plague. recap. any other athlon xp motherboard will also be susceptible to same. nb is fine unless the heatsink actually fell off.

The caps around the VRM are Rubycons and they are fine. Recapping this board will probably make no difference.
Also, not every socket A motherboard needs to be recapped. After the Abit debacle with bad caps, they actually started using good quality capacitors.
For example, I have never seen an Abit NF7 with bad caps. On the other hand, an Abit KT7/KT7A will basically always have to be recapped.

In this case, I'm guessing one of the VRM transistors might be shorted and the PSU is protecting itself when you try to turn it on.
However, the first step should definitely be to try a known good (branded) power supply.

Managed a couple of extra checks, today, and the component tester arrived.

- Rechecking resistances on the MB ATX pins and these look fine
- The PSU powers up on the desk, just jumping the pins
- The CPU fan also powers up with the PSU if I jump PS_ON and GND on the back of the board. It did cross my mind that it's as simple as the case switch, but, jumping the switch pins on the board that the case switch plugs into has no effect.

Interesting to hear differing views on the likelihood that this is 100% capacitor plague. Given the resistances seem okay, and power flows through to board when jumping the pins on the back, is it reasonable to conclude that capacitors are the most likely culprit? I've got the component tester, now, so I guess we'll soon find out once I taken one (some) out.

strange_loop wrote on 2023-09-12, 18:14:

Managed a couple of extra checks, today, and the component tester arrived. […]
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Managed a couple of extra checks, today, and the component tester arrived.

- Rechecking resistances on the MB ATX pins and these look fine
- The PSU powers up on the desk, just jumping the pins
- The CPU fan also powers up with the PSU if I jump PS_ON and GND on the back of the board. It did cross my mind that it's as simple as the case switch, but, jumping the switch pins on the board that the case switch plugs into has no effect.

Interesting to hear differing views on the likelihood that this is 100% capacitor plague. Given the resistances seem okay, and power flows through to board when jumping the pins on the back, is it reasonable to conclude that capacitors are the most likely culprit? I've got the component tester, now, so I guess we'll soon find out once I taken one (some) out.

Its not ment to be powered this way. dont blow something up.
The mainboard handels the ps_on signal. the power button is just a signal for the mainboard to turn on ps_on.
This is why an atx mainboard has standby voltage, to keep the power circuit alive (wich handles the ps_on and power button).

I think nobody can tell you if its the caps. if they fail internally you cant see anything from just looking at them... Anything else is a wild guess...

DerBaum wrote on 2023-09-12, 18:56:

Its not ment to be powered this way. dont blow something up. The mainboard handels the ps_on signal. the power button is just a […]
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strange_loop wrote on 2023-09-12, 18:14:

Managed a couple of extra checks, today, and the component tester arrived. […]
Show full quote

Managed a couple of extra checks, today, and the component tester arrived.

- Rechecking resistances on the MB ATX pins and these look fine
- The PSU powers up on the desk, just jumping the pins
- The CPU fan also powers up with the PSU if I jump PS_ON and GND on the back of the board. It did cross my mind that it's as simple as the case switch, but, jumping the switch pins on the board that the case switch plugs into has no effect.

Interesting to hear differing views on the likelihood that this is 100% capacitor plague. Given the resistances seem okay, and power flows through to board when jumping the pins on the back, is it reasonable to conclude that capacitors are the most likely culprit? I've got the component tester, now, so I guess we'll soon find out once I taken one (some) out.

Its not ment to be powered this way. dont blow something up.
The mainboard handels the ps_on signal. the power button is just a signal for the mainboard to turn on ps_on.
This is why an atx mainboard has standby voltage, to keep the power circuit alive (wich handles the ps_on and power button).

I think nobody can tell you if its the caps. if they fail internally you cant see anything from just looking at them... Anything else is a wild guess...

Fair comment, I did think "this is not a very good idea" so can only blame myself for anything untoward. I should add a self-disclaimer that no one on Vogons shall be blamed for any injury or equipment loss I sustain. . .

strange_loop wrote on 2023-09-12, 19:33:

I should add a self-disclaimer that no one on Vogons shall be blamed for any injury or equipment loss I sustain. . .

Thats said you can power it that way. For example to see if something that is faulty pops, gets hot or voltages get weird.
But you should know how to diagnose a mainboard in that non regular powered state. Maybe lets first stick to the more simple tasks like testing the caps 😀

DerBaum wrote on 2023-09-12, 09:22:

appiah4 wrote on 2023-09-12, 08:59:

rasz_pl wrote on 2023-09-12, 07:01:

Its super rare to get electrolytic cap fail short, and even in those rare instances its mostly due to physical damage. I havent had one in my hands in over 20 years of fixing crap, saw it only once in YT video 😀

It happened to me on a VLB graphics card the other day, resulted in an explosive tantalum capacitor on the power lane as well. Scary. It happens..

Happened to me just a month ago on a 386 Highscreen Laptop.

Electrolytic, tantalums blowing up is normal business.

Well, removing 3 caps from around the VRM allowed me to try out the component tester yielding the following results. The capacitors also all showed a resistance spike on the multimeter before taking the current, ~150 ohms.

tired, but still fine.
Capacitors will not cause motherboard not letting the power supply to turn on, unless those caps are bad in the power supply itself.

I'd check the 1500uF 16v ones. Something tells me those Elite caps aren't original to the board and could be the culprit.

rasz_pl wrote on 2023-09-12, 20:53:

tired, but still fine.

There is one zero missing. 😀

strange_loop wrote on 2023-09-12, 20:42:

Well, removing 3 caps from around the VRM allowed me to try out the component tester yielding the following results. The capacitors also all showed a resistance spike on the multimeter before taking the current, ~150 ohms.

I don't know of any type of 2200uF capacitor that has an ESR of 240mOhm (0.24Ohm).
LowESR will have 10-20mOhm, general use - 30-50mOhm.
The capacitors are residually and irrevocably dead.

shevalier wrote on 2023-09-13, 04:00:

I don't know of any type of 2200uF capacitor that has an ESR of 240mOhm (0.24Ohm). LowESR will have 10-20mOhm, general use - 30- […]
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strange_loop wrote on 2023-09-12, 20:42:

Well, removing 3 caps from around the VRM allowed me to try out the component tester yielding the following results. The capacitors also all showed a resistance spike on the multimeter before taking the current, ~150 ohms.

I don't know of any type of 2200uF capacitor that has an ESR of 240mOhm (0.24Ohm).
LowESR will have 10-20mOhm, general use - 30-50mOhm.
The capacitors are residually and irrevocably dead.

This. I don't want to argue with people like rasz_pl who are obviously way more experienced in things like this (I've fixed a lot of things with his help, thanks and THANKS man!) but I have experienced cases where this will cause a non-power up - incidentally one of those cases was an MSI KT3 Ultra2 (which, after recap, failed in a different matter but I digress). Those capacitors are in the power delivery circuit and a lot of things can go wrong without proper power delivery. I would definitely try the recap; it's not a surefire fix, but it is a good starting point.

appiah4 wrote on 2023-09-13, 05:51:

shevalier wrote on 2023-09-13, 04:00:

I don't know of any type of 2200uF capacitor that has an ESR of 240mOhm (0.24Ohm). LowESR will have 10-20mOhm, general use - 30- […]
Show full quote

strange_loop wrote on 2023-09-12, 20:42:

Well, removing 3 caps from around the VRM allowed me to try out the component tester yielding the following results. The capacitors also all showed a resistance spike on the multimeter before taking the current, ~150 ohms.

I don't know of any type of 2200uF capacitor that has an ESR of 240mOhm (0.24Ohm).
LowESR will have 10-20mOhm, general use - 30-50mOhm.
The capacitors are residually and irrevocably dead.

This. I don't want to argue with people like rasz_pl who are obviously way more experienced in things like this (I've fixed a lot of things with his help, thanks and THANKS man!) but I have experienced cases where this will cause a non-power up - incidentally one of those cases was an MSI KT3 Ultra2 (which, after recap, failed in a different matter but I digress). Those capacitors are in the power delivery circuit and a lot of things can go wrong without proper power delivery. I would definitely try the recap; it's not a surefire fix, but it is a good starting point.

I second and third the thank-yous. Really, this is such a fantastic community. And, in my case that's more than just this situation but about getting more confident to be more involved in repairs and projects in the future, not just old computers. It's also about me sharing this interest and enthusiam with my son, and, maybe, he'll become an electrical engineer one day, or generally have the ability to make and repair - so, thank you for playing a part in that.

Due to my lack of understanding, it hasn't been clear to me (amongst other things) that failed caps can cause a total failure to power-on, but, I'm willing to try the re-cap. Is there anywhere particularly reputable online in the UK I should be getting caps from, any particular brands or pitfalls to watch out for?

shevalier wrote on 2023-09-13, 04:00:

rasz_pl wrote on 2023-09-12, 20:53:

tired, but still fine.

There is one zero missing. 😀

Seen worse still working 😀 certainly wont prevent Vcore supply from functioning in some capacity. Still its irrelevant because from what I understand power supply is not turning on at all. Its like suggesting to replace tires on a car with seized engine.

strange_loop wrote on 2023-09-13, 08:03:

failed caps can cause a total failure to power-on

no
have you tried another power supply?
diagram of the board:

I would start on page 43 with measuring voltage on PS_ON inside ATX connector with power supply connected and while pressing power button/shorting power_button pins, also measure PW_OK voltage

rasz_pl wrote on 2023-09-12, 20:53:

Seen worse still working 😀 certainly wont prevent Vcore supply from functioning in some capacity. Still its irrelevant because from what I understand power supply is not turning on at all. Its like suggesting to replace tires on a car with seized engine.

I totally agree. In fact, I think he should calibrate his component tester if he hasn't already.
I don't fully trust the 0.2 Ω ESR because it seems like that might be the resistance of the tester leads if uncalibrated. Maybe try to test a random film capacitor that should have very close to zero ESR.

If you are in the UK, Farnell or RS Components are probably the obvious choices for ordering capacitors.
But I'm afraid that without further diagnosis of the issue, they will only serve as soldering practice, which is not necessarily a bad thing.

rasz_pl wrote on 2023-09-13, 08:07:

Seen worse still working :) certainly wont prevent Vcore supply from functioning in some capacity. Still its irrelevant because […]
Show full quote

shevalier wrote on 2023-09-13, 04:00:

rasz_pl wrote on 2023-09-12, 20:53:

tired, but still fine.

There is one zero missing. 😀

Seen worse still working 😀 certainly wont prevent Vcore supply from functioning in some capacity. Still its irrelevant because from what I understand power supply is not turning on at all. Its like suggesting to replace tires on a car with seized engine.

strange_loop wrote on 2023-09-13, 08:03:

failed caps can cause a total failure to power-on

no
have you tried another power supply?
diagram of the board: msi_ms-6380e_rev_0b_sch.pdf I would start on page 43 with measuring voltage on PS_ON inside ATX connector with power supply connected and while pressing power button/shorting power_button pins, also measure PW_OK voltage

Thank you. I'll hopefully get a chance to check those voltages out this evening.

I've run through the calibration on the competent tester but before that I did check it with a new capacitor and tested it with the same one again after calibration, getting repeatable results in a very narrow range - I take this as reassurance that the tester itself is reliable unless (again!) I'm missing something. I know reliability/repeatability are not the same as accuracy.

Unused capacitor with results, as shown;

strange_loop wrote on 2023-09-13, 09:29:

Unused capacitor with results, as shown;

Very similar to the truth. But it’s better to check on a 1-10 µF film capacitor. They have, by definition, a very low ESR.

rasz_pl wrote on 2023-09-13, 08:07:

Still it's irrelevant because from what I understand power supply is not turning on at all.

The HIP6301 has 10% line over/under voltage protection of 10%.
V_ripple=▲I*ESR.
If the ESR is 10 times higher, V_ripple can easily cross the voltage protection line. The VRM has a couple of cycles and shutdown. You won't be able to see this with a multimeter only.

strange_loop wrote on 2023-09-13, 09:29:

Thank you. I'll hopefully get a chance to check those voltages out this evening. […]
Show full quote

rasz_pl wrote on 2023-09-13, 08:07:

Seen worse still working :) certainly wont prevent Vcore supply from functioning in some capacity. Still its irrelevant because […]
Show full quote

shevalier wrote on 2023-09-13, 04:00:

There is one zero missing. 😀

Seen worse still working 😀 certainly wont prevent Vcore supply from functioning in some capacity. Still its irrelevant because from what I understand power supply is not turning on at all. Its like suggesting to replace tires on a car with seized engine.

strange_loop wrote on 2023-09-13, 08:03:

failed caps can cause a total failure to power-on

no
have you tried another power supply?
diagram of the board: msi_ms-6380e_rev_0b_sch.pdf I would start on page 43 with measuring voltage on PS_ON inside ATX connector with power supply connected and while pressing power button/shorting power_button pins, also measure PW_OK voltage

Thank you. I'll hopefully get a chance to check those voltages out this evening.

I've run through the calibration on the competent tester but before that I did check it with a new capacitor and tested it with the same one again after calibration, getting repeatable results in a very narrow range - I take this as reassurance that the tester itself is reliable unless (again!) I'm missing something. I know reliability/repeatability are not the same as accuracy.

Unused capacitor with results, as shown;

For this purpose, those AVR based testers are more than accurate enough as is. If you however want another interesting/fun electronics project once you get the computer back to life, there are plenty of fixes, mods, custom firmwares, etc to improve them 😀

Some links:

https://www.eevblog.com/forum/testgear/$20-lc … hecker-project/
https://www.mikrocontroller.net/articles/AVR_ … ransistortester
https://github.com/madires/Transistortester-Warehouse

appiah4 wrote on 2023-09-13, 05:51:

but it is a good starting point.

To measure its all, you need to desolder its. If its are unsoldered, it is easier to solder new ones.
And most of the damage to “aged” hardware occurs precisely due to the fault of capacitors.
Because their failure curve is rising, while that of semiconductors is falling.
I'm also not a fan of soldering old capacitors to preserve appearance.

kaputnik wrote on 2023-09-13, 10:33:

For this purpose, those AVR based testers are more than accurate enough as is.

For repair purposes, it does not matter whether the ESR is 10 mOhm or 30. This is not a development with predict the warranty period of operation.
An indicator is sufficient to indicate that the capacitor is alive.
The capacitors in the photo are dead.

shevalier wrote on 2023-09-13, 10:35:

For repair purposes, it does not matter whether the ESR is 10 mOhm or 30. This is not a development with predict the warranty pe […]
Show full quote

kaputnik wrote on 2023-09-13, 10:33:

For this purpose, those AVR based testers are more than accurate enough as is.

For repair purposes, it does not matter whether the ESR is 10 mOhm or 30. This is not a development with predict the warranty period of operation.
An indicator is sufficient to indicate that the capacitor is alive.
The capacitors in the photo are dead.

My point exactly, as long as the measuring results at least are in the same magnitude as the reality, it's good enough. Hence the suggestion to first resurrect the computer, and then improve the meter if there's interest 😀

rasz_pl wrote on 2023-09-13, 08:07:

Seen worse still working :) certainly wont prevent Vcore supply from functioning in some capacity. Still its irrelevant because […]
Show full quote

shevalier wrote on 2023-09-13, 04:00:

rasz_pl wrote on 2023-09-12, 20:53:

tired, but still fine.

There is one zero missing. 😀

Seen worse still working 😀 certainly wont prevent Vcore supply from functioning in some capacity. Still its irrelevant because from what I understand power supply is not turning on at all. Its like suggesting to replace tires on a car with seized engine.

strange_loop wrote on 2023-09-13, 08:03:

failed caps can cause a total failure to power-on

no
have you tried another power supply?
diagram of the board: msi_ms-6380e_rev_0b_sch.pdf I would start on page 43 with measuring voltage on PS_ON inside ATX connector with power supply connected and while pressing power button/shorting power_button pins, also measure PW_OK voltage

Thanks for the link to the PDF. For PS_ON I'm getting ~5v, for PW_OK it's 0v.