Re: GA-8S655FX with very hot FET
I found the datasheet for the SiS 960 but nothing on the SiS 964 or the complete chipset SiS 655 Fx
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Re: GA-8S655FX with very hot FET
I found yesterday that a friend have the same board. He is having problems but finally found it was couse a bad memory module.
I told him to check the fet that gets so hot and also measure the voltage in the pins.
He told me the FET doesnt get hot and the voltages are the same as the ones I got.
D - 3.32v
S - 1.90v
G - 6.30v
For my understand this indicates that the FET is working fine and there is someting in the FET output that is consuming too much. It could be the southbridge. I need to discard...
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Re: GA-8S655FX with very hot FET
Just ordered the caps for my board. It will take about 10 days to arrive
It may have issues with too new hardware but for me it does what I need to. Dont forget its running in memory from a 700Mb CD only.
Greets
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Re: GA-8S655FX with very hot FET
You can install Ubuntu as a standalone operating system or run it from its Live CD. You can use it as a testing tool as it runs from CD and recognizes quite all hardware out there from CD. Also comes with memtest86 from the live cd.
I recomend it for testing hardware. Try it!...
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Re: GA-8S655FX with very hot FET
Are this Caps good for recapping this board ?
Panasonic [M] FJ 6.3V 1000UF
Rubycon MBZ 6.3V 1500UF
Rubycon MBZ 6.3V 3300UF
Rubycon MBZ 16V 1500UF
Thanks for your help and support
What about the KZG 1000uF 6.3v ? should I replace them also ?Last edited by anonbeat; 09-16-2008, 04:35 PM.
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Re: GA-8S655FX with very hot FET
Problem is that now the board does not POST. It was posting using a 400Mhz Bus CPU but using a 800Mhz Bus CPU does not POST.
I no longer have access to the 400Mhz Bus CPU so now Its not posting.
I used a 1.8Mhz Pentium IV and even could get into the BIOS and load defaults but even in this case it got locked after few minutes.
Using a 3.4Mhz CPU or a 3.2Mhz CPU it does not POST so cant do any test.
I replaced the hotter FET nearest caps with a NH ones I had in other spare board without s...
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Re: GA-8S655FX with very hot FET
Ubuntu is a Linux distribution that loads from CDROM and uses system memory as a Hard Disk. When not all the CD content can be loaded in memory it uses partial content in memory and partial in CDROM. It should load just fine. The board does not need any HD for complete POST.
Im suspecting this Southbridge is fried
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Re: GA-8S655FX with very hot FET
The FET after about 15mins working (without complete POST) had a temperature of 62ÂşC
The SouthBridge had 42ÂşC
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Re: GA-8S655FX with very hot FET
No Im not using any HD at the moment to minimize components. When boot I load Ubuntu or memtest from CD....
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Re: GA-8S655FX with very hot FET
Right now this board only boots with a 400/533 Mhz Pentium IV and not with 800Mhz one, but even when boots it locks after a few minutes. I removed all components but the strictly necesary like video card, memory and a cdrom drive to load Ubuntu or to run memtest86.
When boots you can get into BIOS. I have loaded BIOS safe defaults and rebooted to clear a posible BIOS corruption. I tried to load Ubuntu but got locked loading or just after it finished loading without the posibility to check any error or system log.
Im going to try to...
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Re: GA-8S655FX with very hot FET
Ok figured out that the 1.29v are fine!
As indicated here
the DDR slots needs 2.5v and 1.25v
The controller for the DDR memory voltages is the w83301. The w83301 datasheet have an application circuit which reflects exactly the gigabyte ddr voltage regulators used in this board and looks fine. The datasheet can be downloaded from here .
So I get back to the first FET which gets too hot as the problem.
Thank you all for your help
greets
anonbeat
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Re: GA-8S655FX with very hot FET
Sorry I was wrong...
The mosfet that gets HOT powers the Southbridge SIS964 chip. Other mosfet gives power to the DDR slots and this last is giving 1.29V instead of 2.5volts and is not getting even warm.
This two fets gets power from the 3.3v line.
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Re: GA-8S655FX with very hot FET
Wich one do you suspect it could be the problem ?
How can I check wich ones are faulty ?
Thanks in advance
greets
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Re: GA-8S655FX with very hot FET
The PCI and AGP volts are OK.
Just found this FET is the memory regulator and its not giving the 2.5v but 1.29
Any ideas of what could be the problem this is not giving 2.5 Volts ?
Thanks for all your help
Greets
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Re: GA-8S655FX with very hot FET
The capacitors near the CPU socket in the input VRMs ar
HM 3300uF 6.3v H0411
HM 1500uF 16v H0409
KZG 1500uf 6.3v 39 W(3)
Near the Hotter FET there is a nichicon 1000uF 6.3v A0411
The fet part number is On Semiconductor NTD3055-150 . Its a Power MOSFET 9.0 Amps, 60 Volts N–Channel DPAK
When I power on the system I get this voltages in the FET that gets hot.
D - 3.32v
S - 1.90v
G - 6.30v
Ive tested memory with memtest86 on other system and is...
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Re: GA-8S655FX with very hot FET
I start the system for testing only with memory and cdrom. The memory is working fine. The problem is that it starts and after a few minutes it locks. The fet gets so hot I cant touch it with my finger for more than a second after it have been running for a little while. This is the component that gets hotter. This is what made me think it could be the problem. If you look the area around the fet in picture 1 you can see its darker couse the temp the fet gets.
Im not sure if its the fet or not. I tested the FET with multimeter and...
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Re: GA-8S655FX with very hot FET
Nobody has any idea? do you think I should recap the mobo ? What could I test ?
Thanks in advance
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Re: GA-8S655FX with very hot FET
I can now add that the M104I is a quad differential amplifier and the inputs of the amplifier that handles this FET has 2.89v.
Any ideas ? could this be a badcaps problem ?
Thanks in advance
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GA-8S655FX with very hot FET
Hello,
I have a Gigabyte GA-8S655FX motherboard that do weird things. Start when have been powered off for some time and after a while running it locks.
I have been trying to find what the problem is and found a FET that gets too hot. its near the Ram slots. Its the one in the Picture 1.
This FET gets about 8.6 volts in the gate pin and I think this is wrong. I tracked the pin and it comes from another chip with reference ST M104I that is the one in the picture 2.
The picture 3 is the motherboard.
All the caps in the MB looks good.
Anyone know what...
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