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**PeteS in CA** · 03-25-2006, 12:51 AM

Re: Gigabyte GA-6VTXD - no power?

Sounds like a shorted cap and/or MOSFET in one of the VRMs.

**darklock** · 03-25-2006, 01:10 AM

Re: Gigabyte GA-6VTXD - no power?

I'll check for shorts and post again tomorrow. I hope the MOSFETS are OK, cause I have read that shorted MOSFETS might be bad news for the CPU or North Bridge chip.

I was lucky on another Gigabyte (GA-7VTXE) with shorted MOSFETS and exploded Choyo 330uf 25V caps. I was able to repair that one. One of the MOFSETS had unsoldered itself from the board.

Hope the GA-6VTXD is repairable.

**kc8adu** · 03-25-2006, 06:52 AM

Re: Gigabyte GA-6VTXD - no power?

this post brought to you by a ga-6dtxd with 2 engineering sample 1.4 tuallies.
add an isa mod too.
i would remove cpu's and ram and try again.iirc these are tualatin only.no cumine.
pete hit it dead on.likely a shorted vrm fet.

**darklock** · 03-25-2006, 10:57 AM

Re: Gigabyte GA-6VTXD - no power?

thanks for the additional info. I haven't checked for shorts yet, but I already had the CPUs and RAM and video card removed, and still the same symptoms... CPU fans would twitch or sometimes spin for less than a couple of seconds when power on button was pushed....

should be posting and update later today or tonight.

**darklock** · 03-26-2006, 12:33 AM

Re: Gigabyte GA-6VTXD - no power?

Hello again,

Triple checked all capacitors for shorts, and I could not find any. All of the negative leads were tied to ground, and the positive leads did not short to ground at all. The MOSFETs did not have any shorts between any of the gates, so I assume those are OK to.

If I hold the on/off switch in the on position for a few seconds, and then release it, that is when the fans will get enough power to spin for a couple of seconds.

I also had a POST card and all of the main power leds (+12v, -12V, +5v , -5v)light up when the fans get enough power to spin.

FYI - the MB is out of the case on a sheet of cardboard, the only thing connected is the powersupply, the on/off switch, and Intel CPU fans.

Kind of stumped as to what to check next. Is there a way to trick the powersupply into turning on without depending on the MB powerswitch?

**kc8adu** · 03-26-2006, 07:04 AM

Re: Gigabyte GA-6VTXD - no power?

vrm chip bad and locking a fet on at powerup?crummy pos power supply unable to run this board?
duallies need more power than your normal desktop boards.can you see if vcore and vdimm come up in the short time it runs?no cpu's as a vrm fault can kill them.hint vcore is across the caps near each socket.

**kc8adu** · 03-26-2006, 07:09 AM

Re: Gigabyte GA-6VTXD - no power?

almost forgot.+5stby insuficiant to run it after powerup.some boards need more than others.
post the psu.
if its a 500w 8 oz wonder use it for a wheel chock.naah not even good for that.i crumple them up with my bare hands just for fun.

**darklock** · 03-27-2006, 12:39 AM

Re: Gigabyte GA-6VTXD - no power?

haven't tested vcore or vdimm because the powersupply shuts down too fast.

Tried three different power supplies. 1) Sparke Power 300W 2) generic 230W 3) RaidMax 450W

All three work on other boards, I use the Sparkle Power as my bench supply and it works on every board I ever hooked up to it, (mainly Socket A boards, Intel 440GX with dual PIII 500, P4 2.66 on ECS MB) with the exception of this Gigabyte

The 230W is currently running my P4 2.66 ECS MB. The RaidMax 450W came from a system which runs a Abit KN8 SLI with Atlon X2 4400.

I think the powersupplies I used to test the GA 6-VTXD should have enough power to keep it fired up. If I read the previous posts correctly, the CPU fans should spin up without the CPU and RAM installed right? Besides being shorted (couldn't find any shorted caps though) would a bad cap cause this kind of problem?

**tiresias** · 03-27-2006, 06:58 PM

Re: Gigabyte GA-6VTXD - no power?

Hi darklock,

A really easy test to carry out if you can't locate any shorted mosfets or capacitors, which could at least provide some clue as to where on the board your problem lies:

Using your ohmmeter, try checking for obvious shorts between the pins of the male ATX (20 pin, in your case) power connector on your board. Do this first for between 3.3,5,12,-12,-5,5sb and ground, and subsequently between 'rails', such as 3.3 to 5, 5 to 12, etc.

**darklock** · 03-28-2006, 12:18 AM

Re: Gigabyte GA-6VTXD - no power?

Hello tiresias,

Thanks for that tip. I did find that the resistance between the +5 and ground is only about 830 ohms. It actually starts out much less, and then climbs to about 830 ohms.

Not sure what this means...other than probably the +5 rail is shorting to ground somewhere / somehow...

appreciate any further advice that anyone has.

Thanks.

**Rainbow** · 03-28-2006, 01:42 AM

Re: Gigabyte GA-6VTXD - no power?

That doesn't look bad. It starts low because the caps are not charged yet.

**darklock** · 03-28-2006, 11:59 AM

Re: Gigabyte GA-6VTXD - no power?

Originally posted by Rainbow

That doesn't look bad. It starts low because the caps are not charged yet.

The +5 shorts to ground and then climbs to 830 ohms. Are you saying that the behavior is not suspicious?

**tiresias** · 03-28-2006, 12:55 PM

Re: Gigabyte GA-6VTXD - no power?

Originally posted by darklock

The +5 shorts to ground and then climbs to 830 ohms. Are you saying that the behavior is not suspicious?

I have to agree with Rainbow on this one - don't forget that an entirely non-charged capacitor exhibits extremely low, practically zero resistance between its terminals. The fact that the resistance increases implies a charging capacitor.

Usually a short in, say, one of the PCI slots, will give you a very obvious low-ohm reading which does not meaningfully increase with time.

And Darklock, should find nothing this way, and ever get really desperate about the problem, you could try the more radical method of applying the PSU's lines to the 20-pin ATX connector one by one!

**darklock** · 03-28-2006, 02:01 PM

Re: Gigabyte GA-6VTXD - no power?

Originally posted by tiresias

I have to agree with Rainbow on this one - don't forget that an entirely non-charged capacitor exhibits extremely low, practically zero resistance between its terminals. The fact that the resistance increases implies a charging capacitor.

Usually a short in, say, one of the PCI slots, will give you a very obvious low-ohm reading which does not meaningfully increase with time.

And Darklock, should find nothing this way, and ever get really desperate about the problem, you could try the more radical method of applying the PSU's lines to the 20-pin ATX connector one by one!

I am assuming that you mean to ground the PS_ON line to force the power supply to turn on?

I wonder if there is a logic / IC problem with the board...I was looking at this: http://www.duxcw.com/faq/ps/ps1.htm and I am wondering if this might be the problem. Maybe the circuit which controls the powersupply cannot hold the signal down?

**tiresias** · 03-28-2006, 02:18 PM

Re: Gigabyte GA-6VTXD - no power?

Originally posted by darklock

I wonder if there is a logic / IC problem with the board...I was looking at this: http://www.duxcw.com/faq/ps/ps1.htm and I am wondering if this might be the problem. Maybe the circuit which controls the powersupply cannot hold the signal down?

Let's see... if it were the case, that your PSU is shutting down not due to overcurrent (or outright short circuit of its outputs), but merely because the motherboard is setting PSON high for some reason, this would be easily measurable as, when the system would "shut itself down", you would see:

1. 5Vsb output still present
2. A potential (usually about 5V or so) appearing between PSON and ground.

Check if these are present, 5Vsb is usually purple, while PSON is usually green/turquoise.

I don't know your Gigabyte, but I have seen a few motherboards that will "turn themselves off" in this way should they fail at an early stage of their POST. Such as if their CPU is dead/missing or BIOS severely corrupted.

Let us know

**Rainbow** · 03-28-2006, 02:41 PM

Re: Gigabyte GA-6VTXD - no power?

If PS_ON goes high, then you can try to force it low - use a U-shaped wire to connect PS_ON and GND wires on the PSU's ATX connector (insert the wire from top).

**darklock** · 03-28-2006, 03:45 PM

Re: Gigabyte GA-6VTXD - no power?

1) 5VSB is present with powersupply off
2) 3.3V present at motherboard on/off switch header
3) I shorted the PS_ON to ground and fans spin.
4) Put in my Tualatin 1.4 CPUs (dualie board) and measure output voltage at MOSFETs to be 1.4V which is correct.
5) MB still won't POST, POST card reads "dd" and speaker beeps tones (I think three beeps) stops, and then repeats
6) CPUs are good as they test fine in an Azza Tualatin ready board. RAM is fine as well as they test good also.

Maybe it is time for me to return this Gigabyte board to the person I got from for a refund. I will wait until this Friday before giving them a call (30 day return policy) to see if there are any other ideas that I can test.

Corrupted BIOS? I might try hotflashing the chip in another MB to see if that could be the problem.

Will post results later

Thanks for the advice.

**Rainbow** · 03-28-2006, 03:59 PM

Re: Gigabyte GA-6VTXD - no power?

Try with PCI VGA card and another RAM.

**darklock** · 03-29-2006, 01:21 AM

Re: Gigabyte GA-6VTXD - no power?

Hotflashed the BIOS but still no joy.
Tried an AGP card (I was using a PCI video card previously) and still no power on unless I short PS_ON to ground.
POST card displays dE and speaker beeps 4 rapid beeps, pauses and repeats 4 rapid beeps continuously while POST card cycles between 00 and dE.

I think it is time to give up on this board.....

Any final suggestions before it gets sent back on Friday?

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