Re: ASRock Z68 Extreme 4 can't boot
While I have some low resistance in G-S of upper mosfet of Vcore after power off, I later observed the same thing in Vdisplay and Vtt. So this may not be a problem I guess.
But I also have new findings. This time I tested and repeated it 5 times to make sure it is related to my problem. When the board operate normally (i.e. cpu fan turning, diagnostic LED on, beep sound, UEFI working), Vcore is 1.03V with 2 of 8 phases' mosfet gate have voltage, Vdisplay is 0V with gates also 0V (UEFI doesn't use CPU display is something new to...
senderj
Member
Last Activity: 08-26-2017, 04:10 PM
Joined: 06-30-2014
Location: Hong Kong
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Re: ASRock Z68 Extreme 4 can't boot
To sum up, my last finding was that after every power up, there is a varying resistance between G and S of the[COLOR="Red"] upper [/COLOR]mosfet which changes from 3 ohm to open (or rather 8K6 due to a resistor between them) in a very long time (>10 hrs). This almost-shorted G-S makes reboot fail (Vcore=0V). I cannot proceed any further from here.
However, I did try to figure out the schematic of the VRM and draw it up here. All component values are DMM reading, so it may be the result of a problem on the board rather...Leave a comment:
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Re: ASRock Z68 Extreme 4 can't boot
PWM controller is CHL8328 (data sheet attached) and driver for the gates is CHL8510 (data sheet in #19)...Leave a comment:
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Re: ASRock Z68 Extreme 4 can't boot
Tried the CPU heatsink without clamping, didn't remove the problem. Tried removing the VRM heatsink, same problem. Tried with another PSU again, the board still didn't boot.
Tried keeping the power on time short and measure various points on the board. The Vcore PWM controller works, its Vcc was 12V, all its PWM output were 3.36V. The Vcc of the VRM driver was 11.6V and the PWM input was 3.36V as expected. However, all VRM drivers had HIGATE and LOGATE at 0V all the time, and so were the G of all upper and lower mosfet. All 8 drivers...Last edited by senderj; 08-16-2014, 04:52 AM.Leave a comment:
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Re: ASRock Z68 Extreme 4 can't boot
I missed your post yesterday. Will try the CPU heatsink method tonight if I can. Thanks for the info on the PSU. I had tried using another PSU but the board still failed to boot. But I'll open up the PSU to check the caps. Afterall, I learnt a lot up to now so repairing the board is no longer the only thing I am after.
Late last night I steal sometime to measure the voltage. This time I didn't touch any heatsink. I power up the board with a new CPU, it booted ok and entered the UEFI for about 17-18 sec. and then stopped and then...Last edited by senderj; 08-12-2014, 08:25 PM.Leave a comment:
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Re: ASRock Z68 Extreme 4 can't boot
Sorry, the heatsink I am talking about is the mosfet heatsink, not the CPU heatsink.
The PSU I use is CoolerMaster Silent Pro M600.
Will follow the method to measure V of various points and report here. But it will take sometimes since I have to work OT this week. Will work on the board this weekend.Last edited by senderj; 08-11-2014, 04:32 AM.Leave a comment:
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Re: ASRock Z68 Extreme 4 can't boot
OK. I solder the replacement in, measure the DGS of the mosfet and they are all open. I put in the CPU and RAM, power it up and it works. Everything looked ok and I played around with the UEFI for about 2-3 minutes and believe that I might have fixed it. I put my hand on the VRM heat sink to feel if the temp is normal. At this moment it suddenly reboot and failed. The symptom is exactly the same as the problem I tried to fix before encountering the VRM problem (see Post 1 above): when pressing power on, power on LED ok, cpu fan and case fan turning...Leave a comment:
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Re: ASRock Z68 Extreme 4 can't boot
Confirmed that my CPU was toasted.
Just received my mosfet replacement and about to solder it on the board. Are there anything I should check before I power up the board with a new CPU?Leave a comment:
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Re: ASRock Z68 Extreme 4 can't boot
Tried to remove the mosfet yesterday and this morning. The solder didn't even melt under my 20/200W iron. I ended up cutting off the 4 leads, checked to ensure no connection to the pad (except the D), and then measure all D-S and they are now open. CPU +12V to Gnd is open too.
Still trying to remove the mosfet completely. The D has a large pad at the back and soldered on the board where my iron cannot access. I tried to heat up the D lead with my iron switched to High for 2 minutes, the enclosure of the mosfet went off but the pad...Last edited by senderj; 08-01-2014, 10:05 PM.Leave a comment:
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Re: ASRock Z68 Extreme 4 can't boot
Vcore upper mosfet are circled with red, 8 phrases. All 8 have their D-S shorted. 7 have their D-G & S-G opened but the Q7493 (marked with **) has D-G S-G at 19.4 ohm. Lower mosfet all have D-S 91.6 ohm and D-G S-G opened.
Other VRM next to them are for Vtt and CPU display. Their leads are all opened.
Looks like the Q7493 causes the problem. And my CPU is likely toasted. The mosfet is labeled "9130AL PBm". I think it's from NXP but I am not able to find it in digi-key nor RS. Where else I can look for...Leave a comment:
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Re: ASRock Z68 Extreme 4 can't boot
The board was designed such that same voltage are shorted. My measurement are like this: On the 24-pin ATX, all are open except +3.3V is 161 ohm to gnd with or without CPU. On the 8-pin CPU power socket, +12V is 91 ohm to gnd without CPU and 4.8 ohm to gnd with CPU.
Are they ok?Leave a comment:
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Re: ASRock Z68 Extreme 4 can't boot
Thanks for the reply. Tried power up without CPU & its 12V. Still couldn't turn it on. Measuring the SIO chip, 3VSB ok, PSIN & PSOUT go low in response to the power button, but PSON (to ATX psu) stady at +4.46V. Not able to continue checking the CPU VRM if I can power up the board.
Here is the link to the SIO spec. Page 36, 260 & 261 are where I am learning but not totally understand.
[URL="http://webshop.atlantikelektronik.de/Mailings/NCT6776F_NCT6776D_Datasheet_V1_2.pdf"]http://webshop.atlantikelektronik.de/Mailings/NCT6776F_NCT6776D_Datasheet_V1_2.pdf[/URL]...Leave a comment:
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ASRock Z68 Extreme 4 can't boot
I am trying to fix this board (3 years old) which cannot boot. While measuring voltage at various points, I encountered another problem.
Original problem first. If I leave it untouched for a few days, it boot for 3-4 sec, the 2-digit LED lighted up and changing values, then it went off and only the CPU fan and chasis fan turning, nothing else works. If then I shut it down and restart the power again, only the fans turn and LED never light up.
After studying for months, I now can figure out the VRMs and most of the large components on the board. So I check the connectivity... -
Re: Dell Q14228W 0.8 sec to black
Not able to find this transformer. There are some close to it but the shipping is far more expensive. Ended up buying a replacement board. Checked the resistance of T801, 985 ohm, still lower than the other 997-1003 ohm. Put the board in and the mon lighted up again. Thank you all for your help to make it a success.Leave a comment:
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Re: Dell Q14228W 0.8 sec to black
OK. removed the transformer and measured the secondary to be 710 Ohm and primary 0.3 Ohm. Hunting for replacement. Will update. Thanks for all the help here....Leave a comment:
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Re: Dell Q14228W 0.8 sec to black
If one transformer is down, I would assume 3/4 of the screen would still on. Doesn't it work this way?Leave a comment:
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Re: Dell Q14228W 0.8 sec to black
Thanks. I read the guide before posting the questions.
These are the photos of the back side of the board.
I also measured the R of the transformers still on the board (with DMM at 2K/20M). Unlike most of the photos in this forum, the transformers only has 6 legs. Leg 1-4 at one side and 5-6 at the other.
All are open except
1-2 and 1-4 1M, 1-6 1K except T801 at 725 Ohm
2-4 shorted, 2-6 raising
4-6 risiing
I also have a photo on the label of the transformer 80GL20T-23-DN, but couldn't...Last edited by senderj; 07-03-2014, 08:20 PM.Leave a comment:
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Re: Dynex DX-40L261A12 using CCFL for locating bad inverter xformer
Budm, other than my hands, can I use something else? Like a wire to the E of the power plug?Leave a comment:
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Dell Q14228W 0.8 sec to black
Thank you for the "2 sec to black" post which encourage me to fix my failed mon. Very old (2007) Dell model but the layout is very similar to other Dell in this site. It works for <1 sec and than black. Re-power it gives me another <1 sec and black again. But shining a light on the screen doesn't seems to show any image of the display, not even the OSD. Without connecting to other board, just power up the psu and checked the psu board all +5V and +12V are working when without loading, but there is no high voltage from the inverters.
I have a few questions about... -
Re: New Members - please post your introductions here
Hi there! new here. In software profession but weak in hardware. Interested in electronics since child but don't have the proper training. Self study on-going, and on-going for years but still can't say I know (still can't repair 90% of failed electronics at home). Assembled a few kits on Hifi amp, cd player, speakers by following instructions. Understand their principle, sometimes understand their schematics if explained in detail.
Can't say I would contribute much now because of the limited knowledge. But I would...Leave a comment:
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