Biostar P4M800PRO-M7 NO POST

[Mike Jenk]

So I got this board which was working find, then it cut off and would not come back on. Caps around CPU where vented , so I replaced them around CPU area temporary to see if it would boot up. before doing this I tested the power supply and even changed out the power supply to ensure that was not it. What I have after wards is same thing , so with the power supply hooked up and taking a reading at the green wire when connected to board I have 5.02 volts and then when i turn board on goes to 0.00 and have no voltages any where and seems to possibly trip the power supply off,as if there is a dead short, i have to unplug power supply to get my power back. So when trying to follow testing the VMR is where I get lost due to lack of expertise. I am thinking Its one of the regulators or transistors ,but when I try to omh out from connection of pins on JATXPWR1 to source side of each regulator i get readings ranging from 300 to 1 meg . Is Q100,Q82 AND DQ 45 the reg? I took the reading from the S side and G side they would stary high and end low . So if some one could point out what I am doing wrong it would be great, I know I left some info out, Just let me know what you need.

[RJARRRPCGP]

Re: Biostar P4M800PRO-M7 NO POST

At least, the socket don't look shitty like my DOA Asus Maximus II Gene.

[Mike Jenk]

Re: Biostar P4M800PRO-M7 NO POST

Can some one help me find these 2 replacement parts ?

On PQ 5 in the pic is obsolete not sure what would replace it.

On Q49 looks like a RichTek Rt9161/A ? cant find that neither.

Thanks..

[Mike Jenk]

Re: Biostar P4M800PRO-M7 NO POST

Can some one help me find these 2 replacement parts ?

On PQ 5 in the pic is obsolete not sure what would replace it.

On Q49 looks like a RichTek Rt9161/A ? cant find that neither.

Thanks..

Any body with any suggestions to those replacement , Voltage regs and Transistors?? I found some but the input capatance is differant...

[SIDMX]

Re: Biostar P4M800PRO-M7 NO POST

Hi Mike.

...Is Q100,Q82 AND DQ 45 the reg?

No, all of them are from diferent circuits, Q100 is part of VTT circuit, Q82 is part of VDIMM circuit, and Q45 is part of AGP and NB voltage circuits.

...On PQ 5 in the pic is obsolete not sure what would replace it.
On Q49 looks like a RichTek Rt9161/A ? cant find that neither.

For PQ5 you will be fine with FDD8880, Q49 is CEU61A3 Mosfet, suitable replacement: STD44N4LF6.
Make sure your temporary/testing caps are good, mosfets fail when overstressed because of bad caps, are you sure Q49 is bad? Q49 is in RAM VDIMM circuit and it is not so common for those to fail, if it is bad replace the 4 big caps next to the ram slots too.
Search the forums for info regarding VRM and Mosfet testing procedures, you will find all the info you need.

Good luck!

[Mike Jenk]

Re: Biostar P4M800PRO-M7 NO POST

Hi Mike.
No, all of them are from different circuits, Q100 is part of VTT circuit, Q82 is part of VDIMM circuit, and Q45 is part of AGP and NB voltage circuits.

Search the forums for info regarding VRM and Mosfet testing procedures, you will find all the info you need.

Good luck!

Yeah I was trying to use the VRM testing procedure by AKOR on this forum, but since I am not sure which is the VRM circuit all my testing is in vain. I thank you for the response any other help would be great.

[SIDMX]

Re: Biostar P4M800PRO-M7 NO POST

Yeah I was trying to use the VRM testing procedure by AKOR on this forum, but since I am not sure which is the VRM circuit all my testing is in vain...

Just be patient and read again the whole AKOR thread, all info is in there, even aplication notes of VRM circuit, for MOSFET testing read this ...don't give up mate, I came to BC forums three years ago with practically no background in electronics and even tought i'm still learning, I'm now fixing PSUs, Motherboards and VGAs, so my advise is read, read, read and then read some more.

CPU VRM circuit in modern boards is always around the processor socket, VRM circuit is composed by lots of parts, for simplicity let's say it is composed from capacitors, coils, mosfets, mosfet driver chip and a buck controller chip or sometimes like in your case a single chip ISL6566 that is a combination of mosfet driver and buck controller in a single package, always remember that if something fails there is always a good cause so before attempting to replace the bad part check all other components in the circuit or you you may end up burning the new part again and possibly causing more damage to your board.

Take a look a the AKOR thread and ISL6566 datasheet and you will be able to find the location of VRM circuit and it's basic components in you board. IMHO the most possible causes for blown mosfets are: bad caps in PSU, bad VRM input caps, bad VRM output caps, failing mosfet drivers, failing buck controller ...and only one time i found a very small shorted smt cap that was the cause of mosfets going bad.

[Mike Jenk]

Re: Biostar P4M800PRO-M7 NO POST

Take a look a the AKOR thread and ISL6566 datasheet and you will be able to find the location of VRM circuit and it's basic components in you board. IMHO the most possible causes for blown mosfets are: bad caps in PSU, bad VRM input caps, bad VRM output caps, failing mosfet drivers, failing buck controller ...and only one time i found a very small shorted smt cap that was the cause of mosfets going bad.

Thanks, lots of reading to do. Did not even know about this chip, will keep posted on results. will need to fix the mobo board I am using now, after recapping one of the caps at the PCI slot is venting only lasted about 3 weeks.

[Mike Jenk]

Re: Biostar P4M800PRO-M7 NO POST

Will got a round to unsolder the leg on each mossfet today and sure enounh half of them are shorted. Dont know how this was even working. I was using this thing up until it just turned off. Let you know how it turns out after installing new ones.

[SIDMX]

Re: Biostar P4M800PRO-M7 NO POST

How is it going Mike?

[Mike Jenk]

Re: Biostar P4M800PRO-M7 NO POST

did get my parts in. Have not had time to install yet, but most likely this weekend , will let you know how it turns out.

[Mike Jenk]

Re: Biostar P4M800PRO-M7 NO POST

Stuck the Voltage Regulators and all the MOSFETs in around CPU and now it post on bench, so at least it powers on now and will hook it all back up later to see how it is working. If test out OK will finish recaping the rest of the board.

Thanks for the help,
Mike

[jbonavita]

Re: Biostar P4M800PRO-M7 NO POST

I know this is old, but I have a missing cap on the same board, is the first one under the copper bobin, to the rigth of the ps2 connector and the 4 pin power supply connector.
Thanks in advance.

[racecar56]

Re: Biostar P4M800PRO-M7 NO POST

I know this is old, but I have a missing cap on the same board, is the first one under the copper bobin, to the rigth of the ps2 connector and the 4 pin power supply connector.
Thanks in advance.

On my friend's Biostar P4M800-M7 (not Pro), this is an 1800uF 16V TK ATWY.



I hope this helps.