FX505DT IT8987E

[trepachka]

My motherboard - FX505DT - has IT8987E BXS chip which I need to replace. A local seller has IT8987E BXA chip for sale. Can I get it or must I have the chip with BXS marking on it to match what's on the motherboard?

[mcplslg123]

Re: Asus tuf FX504gm troubleshooting

BXA-The last letter "A" stands for Always
BXS-The last letter "S" stands for Suspend

Now decide for yourself.

[trepachka]

Re: Asus tuf FX504gm troubleshooting

Can you give me a straight answer to my question? Must I use the exact match "BXS" or can I use "BXA" as well?

[kalilinux25]

Re: Asus tuf FX504gm troubleshooting

Can you give me a straight answer to my question? Must I use the exact match "BXS" or can I use "BXA" as well?

Just use the same chip model printed

[mcplslg123]

Re: Asus tuf FX504gm troubleshooting

Can you give me a straight answer to my question? Must I use the exact match "BXS" or can I use "BXA" as well?

I've explained the difference between two suffix. Cant give a clear answer as on some platforms, they are inter changeable and on others they dont work. Since there is no way to know whether they will work after suffix swap,no one can give you an aswer in YES or NO. I always match the suffix to avoid swapping the SIO twice for non compatibilty. So once again choice is yours.

[trepachka]

Re: FX505DT IT8987E

I ordered the exact match and it should be here in 2 weeks.

[mcplslg123]

Re: FX505DT IT8987E

Wise decision.Btw, what is the issue with your MB?

[trepachka]

Re: FX505DT IT8987E

The motherboard is completely dead. I get no lights, nothing. The 19v rail is present. I found the IC chip shorted, ordered the new chip from China 2 weeks and had it installed today. The short where I found it is no longer there. However, the motherboard is still dead. I only get 19v line. I am looking for suggestions. Thanks.

[rediii]

Re: FX505DT IT8987E

The motherboard is completely dead. I get no lights, nothing. The 19v rail is present. I found the IC chip shorted, ordered the new chip from China 2 weeks and had it installed today. The short where I found it is no longer there. However, the motherboard is still dead. I only get 19v line. I am looking for suggestions. Thanks.

be aware of fake chips. nowadays it is a really big problem and best would be to harvest chips from dead motherboards...

[trepachka]

Re: FX505DT IT8987E

Looks like the issue is with dc line 1st mosfet. I checked both mosfets and they are good. The gate on the 1st mosfet is showing 0V. Please, correct me if I am wrong. The gate should get about 10v and it is powered by SM4511NHKPC-TRG chip (ACDRV, pin 4). There is a resistor between the gate and ACDRV and it measures 4K Ohms which is correct.

So, does it mean the SM4511NHKPC-TRG chip is not enabled or may be faulty? Can someone suggest what I need to check next? I do not have enough knowledge to proceed from this point on.

Thanks.

[trepachka]

Re: FX505DT IT8987E

I forgot to mention that I am referring to bq24780S chip.

The following pin measurements were taken:

ACDET (pin 6)=2.7V
VCC (pin 28)=19.43V
PHASE (pin 27)=0.4V
HIDRV (pin 26)=0.4V
BTST (pin 25)=1.35V
REGN (pin 24)=1.42V

It is my understanding ACDET is higher than 2.4V. So, unless there is a short on the motherboard, the chip is supposed to provide power to 1st and 2md mosfet to open the gates. I have not been able to find any shorts at this moment.

[mon2]

Re: FX505DT IT8987E

REGN (pin 24)=1.42V

This is a low voltage and is an internal LDO that should offer 6 volts.

Locate and remove the ~4k resistor on the ACDRV pin. Flux it and remove with care using tweezers. Do not lose the part.

What is the voltage to ground now of REGN pin? ACDRV pin?

ACDRV should be ~25 volts but will only be this boosted value if REGN is ~6 volts.

Remove all power and measure the resistance to ground of the REGN pin.

If the resistance is not low, suspecting that this charger IC is defective and will need to be replaced. Common to source on Mouser / Digikey / Aliexpress and many other sites.

https://www.mouser.com/ProductDetail...NvLnK4Wg%3D%3D

[trepachka]

Re: FX505DT IT8987E

REGN pin resistance to ground is 60 ohms with a capacitor between the pin and ground. I ordered the chip and it should be here in a couple of days. I will test all of this then. At this point I suspect this chip is faulty but I will find out soon.

[mon2]

Re: FX505DT IT8987E

Agreed. Remove the cap and check if the resistance increases or not. It is way too low for this LDO rail. If the resistance increases to be much higher, then the cap is clearly shorted and needs to be replaced. Without the cap the LDO should return to ~6 volts.

Next suggestion is the same, replace this charger IC.

[mcplslg123]

Re: FX505DT IT8987E

Before ordering the charger IC
01.Remove the cap on REGN pin and check resistance to GND again
02.If resistance remains same after step#1,remove the charger IC and repeat the measurement.
03.Order the charging IC if resistance increases significantly after step#2.

[trepachka]

Re: FX505DT IT8987E

The chip arrived yesterday and I had it soldered in. ACDET pin reads 2.7V, VCC pin reads 20.4V, REGN pin reads 6V, ACDRV reads about 26V. I checked some coils and was able to detect 5V, 3.3V ad 1.8V power rails. So, I had the computer fired up. The keyboard kept cycling yellow letters on and off, on and off. I had the computer turned off. I checked the readings on the chip and while REGN pin still reads 6V, ACDRV went to 0V. I left the motherboard for an hour or so. I came back and had the charger plugged in. ACDRV went to 26V again for about 10 seconds or so and then went to 0V again.

I am just wondering if I have a faulty chip?

[mcplslg123]

Re: FX505DT IT8987E

May be soldering of the chip is the issue.Check once more.

[trepachka]

Re: FX505DT IT8987E

I visually inspected the soldering, also make sure each pin was connected to other components. I found IT8987E BXS that I replaced recently, several pins are now loose. I have not soldered them back to the board. Just wondering whether this could also pull the voltage on ACDRV down to 0V. I am sorry for all the questions. I am really new to this.

[mon2]

Re: FX505DT IT8987E

Remove the 4k resistor on the ACDRV pin. Do not lose this resistor.

Power up again and check the ACDRV voltage at the charger IC pin.

Is it now ~25v and stable?

[mcplslg123]

Re: FX505DT IT8987E

I visually inspected the soldering, also make sure each pin was connected to other components. I found IT8987E BXS that I replaced recently, several pins are now loose. I have not soldered them back to the board. Just wondering whether this could also pull the voltage on ACDRV down to 0V. I am sorry for all the questions. I am really new to this.

If SIO is not soldered properly, the motherboard can behave absurd. Use good quality flux and touch up all the pins of SIO properly. Clean the area with IPA then check whether any pin is still loose. Post a clear pic of SIO soldering before doing anything and then again after the touchup job.