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Old 08-03-2017, 01:20 PM   #1
Dan81
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Default ECS K7VZA - strange behaviour after recap

Another freebie from the strange package I've explained in the best cheap/free scores thread.


This one came to me with all the VRM G-Luxons bulging. Literally EVERYTHING around that place (aside from a small 1000uF 6.3v G-Luxon which wasn't bulged at all, but close to the caps that bulged ) was bulging. Other caps that were away from the VRMs were fine and not bulging or out of spec. Before recapping, the board would simply not POST or beep regardless if RAM or GPU was present, meaning it wouldn't detect the CPU at all.

I recapped the board and got rid of every G-Luxon. VRM low and high got a mix of OST RLX (2007 datecode, barely used) and Rubycon MBZ 3300uF 6.3v caps. (I used what I had available.) I used known good caps, to eliminate any possibility of using a dud cap. Most of the RAM caps are MBZ, with the AGP slot and PCI slots below having OST RLX.

Anyways the symptoms are these:

-will not POST with RAM installed - no beeps at all. Not even the missing GPU beep.
-will beep if there is no RAM installed - I get the continuous beeps signaling no RAM present in slots

I've used every known good (meaning one that POSTs with all my other boards I own) PSU I've had in the house. Same symptoms.

Anything I could possibly try? I'd guess it hangs somewhere on the C1 POST code ( I have no possibility to find a POST card here, so don't ask.) or after that.

I should mention I've also tried about 5-6 different SD-RAM sticks of various speeds (PC100 and 133.) with no result.
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Old 08-03-2017, 02:43 PM   #2
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Default Re: ECS K7VZA - strange behaviour after recap

What CPU are you using for testing?
Note depending on what revision the PCB is it supports different processors:
http://soggi.eu/motherboards/ecs-eli.../K7VZA-3.0.htm
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Old 08-03-2017, 05:31 PM   #3
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Default Re: ECS K7VZA - strange behaviour after recap

Maybe the dc-dc converter doesn't like a too low ESR.
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Old 08-04-2017, 12:20 AM   #4
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Default Re: ECS K7VZA - strange behaviour after recap

Quote:
Originally Posted by Per Hansson View Post
What CPU are you using for testing?
Note depending on what revision the PCB is it supports different processors:
http://soggi.eu/motherboards/ecs-eli.../K7VZA-3.0.htm
Athlon 1133 T-Bird. It's a black Rev 3.0 board. (I only had Rev 3 boards through my hands, no 1.0s)

Quote:
Originally Posted by cpt.charlie View Post
Maybe the dc-dc converter doesn't like a too low ESR.
All the caps that were bulged were G-Luxons 2200uF 6.3v.

I'll look up both the specs for the replacement caps and for the G-Luxons so I can find out what ESR they had.

But still... if it would have been the ESR, wouldn't the board actually not beep at all? (meaning no beep at all regardless if there's RAM or GPU - just as if the CPU wasn't installed.)

Last edited by Dan81; 08-04-2017 at 12:23 AM..
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Old 08-04-2017, 03:20 AM   #5
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Default Re: ECS K7VZA - strange behaviour after recap

Inspect the motherboard carefully for any ripped or damaged traces, especially around the edges. Some people handle their boards very carelessly.

Also check the CPU output voltage. Should be 1.65V or 1.75V for that t-bird, if I am not mistaken.

That leads me to ask: are there any jumpers for setting the CPU voltage or frequency? If yes, double-check them. Also check any other jumpers that the board has - not only if they are in the right position but if they are functional as well. I had a board refuse to post because one of the jumpers was slightly damaged on the bottom and not making good contact.

Quote:
Originally Posted by cpt.charlie View Post
Maybe the dc-dc converter doesn't like a too low ESR.
That shouldn't be an issue. Though I will note that most ECS motherboards from that era had a fairly low-frequency switching CPU VRM, typically controlled by a KA7500 PWM chip and having 6x 2200 uF caps on the output of the CPU.

As a test, Dan81 could also try just 3x 2200/3300 uF caps on the CPU output if their ESR specs are much more superior to the G-Luxons.
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Old 08-04-2017, 04:24 AM   #6
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Default Re: ECS K7VZA - strange behaviour after recap

Quote:
Originally Posted by momaka View Post
Inspect the motherboard carefully for any ripped or damaged traces, especially around the edges. Some people handle their boards very carelessly.
I did that from the very beginning. No traces were broken. For a fact it came with foam under it in the box,and it was looking pristine (save for the bulged G-Luxon LZ caps.)

Quote:
Originally Posted by momaka View Post
Also check the CPU output voltage. Should be 1.65V or 1.75V for that t-bird, if I am not mistaken.
Where can I measure the voltage? On the VRM low caps?

And by the way VCORE is present, or else I wouldn't get any beeps. (as I said, the board WILL beep if there is no RAM)


Quote:
Originally Posted by momaka View Post
That leads me to ask: are there any jumpers for setting the CPU voltage or frequency? If yes, double-check them. Also check any other jumpers that the board has - not only if they are in the right position but if they are functional as well. I had a board refuse to post because one of the jumpers was slightly damaged on the bottom and not making good contact.
I used good jumpers that make contact. And no, there's no voltage jumper for the CPU - just for FSB - 100 or 133.

Quote:
Originally Posted by momaka View Post
That shouldn't be an issue. Though I will note that most ECS motherboards from that era had a fairly low-frequency switching CPU VRM, typically controlled by a KA7500 PWM chip and having 6x 2200 uF caps on the output of the CPU.

As a test, Dan81 could also try just 3x 2200/3300 uF caps on the CPU output if their ESR specs are much more superior to the G-Luxons.
Here's the ESR specs for the caps I used, straight out their datasheets. The MBZ and RLX are the caps I used to recap the bulging LZ caps.

Rubycon MBZ: 0.012 ohms (4 used on mobo)
OST RLX: 0.014 ohms (8 used on mobo)
G-Luxon LZ: 0.025 ohms (the ones I pulled out and were bulging.

EDIT:

Voltages measured:

VRM high: 4.65V
VRM low: 1.78V (this must be VCORE as momaka said)
SD-RAM: 3.22V (makes sense since it runs at 3.3v)

Last edited by Dan81; 08-04-2017 at 04:33 AM..
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Old 08-04-2017, 05:16 PM   #7
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Default Re: ECS K7VZA - strange behaviour after recap

Quote:
Originally Posted by Dan81 View Post
And by the way VCORE is present, or else I wouldn't get any beeps. (as I said, the board WILL beep if there is no RAM)
That's true, but it is always worth checking aways. Sometimes, you just don't know if it too low but the board is still trying to boot with that. In which case, anything would be possible as an error.

Quote:
Originally Posted by Dan81 View Post
I used good jumpers that make contact.
Good.

Quote:
Originally Posted by Dan81 View Post
And no, there's no voltage jumper for the CPU - just for FSB - 100 or 133.
I assume you tried both.
In any case, use 100 MHz for now, as that is typically the failsafe FSB.

Quote:
Originally Posted by Dan81 View Post
Here's the ESR specs for the caps I used, straight out their datasheets. The MBZ and RLX are the caps I used to recap the bulging LZ caps.

Rubycon MBZ: 0.012 ohms (4 used on mobo)
OST RLX: 0.014 ohms (8 used on mobo)
G-Luxon LZ: 0.025 ohms (the ones I pulled out and were bulging.
So looks like the caps have about half the ESR. In that case, try running with half the caps. I doubt the issue will be ESR-related, but if you run out of ideas and nothing else works, this would also be worth a try, I think. And in any case, if the board is dead, you probably would be pulling the caps from it anyways to use for something else.

Quote:
Originally Posted by Dan81 View Post
Voltages measured:

VRM high: 4.65V
VRM low: 1.78V (this must be VCORE as momaka said)
SD-RAM: 3.22V (makes sense since it runs at 3.3v)
4.65 Volts on the VRM high side... really?!? That is quite a major drop. Double-check that. If that is correct, double-check the 5V rail coming out of the PSU. I know you said you tested several different power supplies, but if all drop down to less than 4.75V on the 5V rail under load, that's an issue right there! ATX spec says no more than +/- 0.25V on the 5V and 5VSB rails (5%).

Other than that, the VRM low and SD-RAM voltages seem okay.

The only other voltages you need to check is Northbridge Vcc and AGP. For the AGP, there should be a MOSFET or linear regulator near the slot somewhere outputting 1.5V. Looking at the pictures for this motherboard, I see there is one (FET/regulator) right under the lower-end of the slot.

The Northbridge may or may not have its own regulator. On some boards, the Northbridge is fed from the CPU V_Core (VRM low). And on others, depending on how power-hungry the NB is, it may have a dedicated buck VRM (with a inductor, like the CPU) or just a regular linear regulator / MOSFET. Again, looking at pictures of this board, I don't see any regulators or MOSFETs nearby, so either the NB is fed from CPU V_core *OR* one of the four phases near the CPU is actually a dedicated phase for the NB. Thus, check if the inductors near the CPU are all connected together by means or resistance test (but without the CPU). If connected, you should get less than an Ohm, or whatever is the lowest resistance your multimeter can show.
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Old 08-05-2017, 02:20 AM   #8
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Default Re: ECS K7VZA - strange behaviour after recap

Quote:
Originally Posted by momaka View Post
4.65 Volts on the VRM high side... really?!? That is quite a major drop. Double-check that. If that is correct, double-check the 5V rail coming out of the PSU. I know you said you tested several different power supplies, but if all drop down to less than 4.75V on the 5V rail under load, that's an issue right there! ATX spec says no more than +/- 0.25V on the 5V and 5VSB rails (5%).
Yeah, with the MB as load, the voltage goes down between 4.75V (on main ATX cable) and 4.93V on other Molex plugs.


Quote:
Originally Posted by momaka View Post
The only other voltages you need to check is Northbridge Vcc and AGP. For the AGP, there should be a MOSFET or linear regulator near the slot somewhere outputting 1.5V. Looking at the pictures for this motherboard, I see there is one (FET/regulator) right under the lower-end of the slot.

The Northbridge may or may not have its own regulator. On some boards, the Northbridge is fed from the CPU V_Core (VRM low). And on others, depending on how power-hungry the NB is, it may have a dedicated buck VRM (with a inductor, like the CPU) or just a regular linear regulator / MOSFET. Again, looking at pictures of this board, I don't see any regulators or MOSFETs nearby, so either the NB is fed from CPU V_core *OR* one of the four phases near the CPU is actually a dedicated phase for the NB. Thus, check if the inductors near the CPU are all connected together by means or resistance test (but without the CPU). If connected, you should get less than an Ohm, or whatever is the lowest resistance your multimeter can show.
I tested AGP and NB voltages:

AGP: 3.28v with no GPU
1.49v with FX5500 GPU
NB: 3.28v

I measured the pins on three 10uF 25v capacitors very close between the NB heatsink and the main 20 pin ATX connector. As for AGP, I did the same with the nearest 6.3v cap it had.
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Old 08-09-2017, 06:44 AM   #9
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Default Re: ECS K7VZA - strange behaviour after recap

Quote:
Originally Posted by Dan81 View Post
Yeah, with the MB as load, the voltage goes down between 4.75V (on main ATX cable) and 4.93V on other Molex plugs.
That is a pretty sad voltage drop. Definitely something suspicious going on with PSU or motherboard.

Quote:
Originally Posted by Dan81 View Post
I tested AGP and NB voltages:

AGP: 3.28v with no GPU
1.49v with FX5500 GPU
Good.

Quote:
Originally Posted by Dan81 View Post
NB: 3.28v
Hmmm. :\ I know this is an old motherboard, but I still wouldn't expect the NB to run on 3.3V. More like 2.5V max, if even that. Those 10uF 25V caps you were measuring may be connected to a secondary rail going to the NB (as this is an old AMD motherboard, the NB likely needs a secondary rail of 3.3V to communicate with the SD-RAM, because all SD-RAM transactions go trough NB as opposed directly through CPU with newer AMD chips with integrated memory controllers and DDR1/2/3/4 RAM.) Flip the board on the back and see if there are any large traces under the NB connecting it to the CPU V_core rail.

Other than that, I am out of ideas for now what the problem may be. With all of the heat waves going through your region right now, maybe give the motherboard a soapy bath and let it dry in the sun for a few days. If nothing else, at least you will have a shiny-looking motherboard to hang on the wall as an art piece.
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Old 08-10-2017, 03:14 AM   #10
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Default Re: ECS K7VZA - strange behaviour after recap

Quote:
Originally Posted by momaka View Post
Hmmm. :\ I know this is an old motherboard, but I still wouldn't expect the NB to run on 3.3V. More like 2.5V max, if even that. Those 10uF 25V caps you were measuring may be connected to a secondary rail going to the NB (as this is an old AMD motherboard, the NB likely needs a secondary rail of 3.3V to communicate with the SD-RAM, because all SD-RAM transactions go through NB as opposed directly through CPU with newer AMD chips with integrated memory controllers and DDR1/2/3/4 RAM.) Flip the board on the back and see if there are any large traces under the NB connecting it to the CPU V_core rail.

Other than that, I am out of ideas for now what the problem may be. With all of the heat waves going through your region right now, maybe give the motherboard a soapy bath and let it dry in the sun for a few days. If nothing else, at least you will have a shiny-looking motherboard to hang on the wall as an art piece.
No traces that I can see go to the CPU V_core rail. I did find another cap inbetween the SDRAM and NB of the same value (10uF 25v) that measured about 1.12v. Might help you I guess?
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Old 08-10-2017, 03:28 PM   #11
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Default Re: ECS K7VZA - strange behaviour after recap

1.12V is too low for anything on a motherboard that old. Might be worth investigating.

Research online shows that this motherboard has a VIA VT8363A for the NB. So I stand corrected: 3.3V for this NB is indeed in spec, as the VT8363A apparently can take up to 5.5V Vcc.

I suppose it's time to wash 'n' dry the motherboard and see what happens.
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