Re: Dell Precision M3800 won't turn on
I am chasing my tail. Now the board that was working is no longer working and also has the problem of switching itself off about 4 seconds after pressing the power button. Just before this started I pressed the power button, the keyboard backlight was flickering, and then after longer than 4 seconds the laptop shut off. Then the next time I tried the power button the laptop ran for only 4 seconds and shut itself off.
Also, the board I was originally working on, again, doesn't have +5VALW and +3VALW. This time PU300 isn't hot so...
TopPop
Member
Last Activity: 04-01-2023, 10:53 PM
Joined: 07-14-2014
Location: Shelley, Idaho
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Re: Dell Precision M3800 won't turn on
I replaced the resistor. It split in half as I took it off the board. After replacing the resistor the board still wasn't running. It still powers on for about 4 sec and then switches off with power only from the AC adapter. The MOSFETs PQ200 and PQ201 still weren't doing their thing. I referred back to piernov's 2.1.5. Missing Voltage On The Charger IC in the stickied Laptop Battery Charging Circuit thread and I had a look at [url]https://cdn.badcaps-static.com/pdfs/937b4df9cf7e4e5c6531f245f6294b0e.pdf[/url] Basically, I was missing CMSRC,...Leave a comment:
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Re: Dell Precision M3800 won't turn on
Actually, I haven't been in to Windows on this laptop. Just got in to the Dell Diagnostics. It is a pre-Windows thing.
VCC going in to PU200 is supposed to be about 19V. Also, I noticed that PR213 on the broken board looks a bit off. It's numbers on the surface are gone and the center has a light area. I measured its resistance and got 12.7K Ohms but the schematics say it should be 10 Ohms. Included is a pic of the bad resistor and a pic of a good resistor on the working board. Maybe this will help someone. The bad...Last edited by TopPop; 03-15-2023, 10:31 PM.Leave a comment:
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Re: Dell Precision M3800 won't turn on
Readings taken with charger only for power.
VCC is 2.9V
ACDET is 2.7V
ACOK is 0V
ACDRV is 0V
So with nothing coming out of PU200 on ACDRV the PQ200 and PQ201 mosfets don't do their thing. Do I have that correct?Last edited by TopPop; 03-14-2023, 09:49 PM.Leave a comment:
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Re: Dell Precision M3800 won't turn on
Hey, thanks for replying! Not sure why but I didn't get an email when you replied.
PU300 died for some reason. It was weirdly hot. That took out +3VALW and +5VALW. Got a replacement IC and put it on the board and now +3VALW and +5VALW are back. I checked that by checking the voltages from PL300 to ground and PL301 to ground.
Prior to PU300 dying I had the laptop running off the battery without the charger. If I had the battery and charger plugged in then the laptop ran and charged the battery. The only...Last edited by TopPop; 03-14-2023, 09:06 PM.Leave a comment:
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Re: Dell Precision M3800 won't turn on
Unfortunately something new went wrong. I no longer have +3VALW and +5VALWLeave a comment:
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Re: Dell Precision M3800 won't turn on
So after some more checking I found the laptop will now charge a battery from the AC adapter, will run off the battery, will run with the battery and AC adapter plugged in, but will not run from only the AC adapter. With only the AC adapter connected for power, if I press the power button, the light in the button turns on for about 4 seconds and then shuts off.
PQ102 was suspicious. It had 13.5V on the drain, source, and gate and the body diode seemed to be bad. I replaced it. However, that did not fix the problem of the laptop...Leave a comment:
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Re: Dell Precision M3800 won't turn on
I know I have +3VALW and +5VALW but I'm missing any fan activity and no screen graphics or backlight when the power button is pushed. I was looking at page 51 of the schematics. So I thought maybe I am missing +3VS and +5VS. I went looking for QZ8 but found that was removed and replaced by TI TPS22966 and some other components were added in as stated on page 50.
I went to page 34 and saw UZ4 also known as TPS22966. On the board it has +5VALW and +3VALW going to it but when I press the power button there is no +5VS and +3VS going...Leave a comment:
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Re: Dell Precision M3800 won't turn on
I got the replacement battery. The other working M3800 has no issues with the AC adapter that I've been using with the broken M3800. It charges the battery too. The problem with the non-working M3800 is not the AC adapter.Leave a comment:
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Re: Dell Precision M3800 won't turn on
The AC adapter I have probably isn't the original but it is one that is compatible with this laptop. I have another M3800 that is in a better working state than the one I've been working on. This second one reports that the battery has permanently failed. It has adapter warnings enabled in the BIOS setup and doesn't complain about the AC adapter. It boots in to Windows. I've ordered a battery replacement for this one. Should arrive early next week. Basically, I've tried this AC adapter with another M3800 and it seems to work though I admit...Leave a comment:
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Re: Dell Precision M3800 won't turn on
I got it back to where it belongs. See photo. Plus, I made sure there is continuity between the capacitor ends and pins 2 & 3 of U4 like there should be and I made sure I didn't short the capacitor somehow.
Though, that didn't fix the problem. I press the laptop power button and see a power light for about 4 seconds, no keyboard backlight and no screen backlight, and then the laptop switches itself off....Leave a comment:
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Re: Dell Precision M3800 won't turn on
A couple more pics. I think that's the best I can do for quality.
Maybe I need to just gently push the cap pad back in to its spot, reflow the connection points, and then get some UV setting conformal coating to keep it in place.
Or, I have some spare 10uF 25V 0805 caps. I could put one running diagonally from pin 3 to CT44's pad that is still on the board....Leave a comment:
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Re: Dell Precision M3800 won't turn on
I guess I somehow caused this damage while taking the board out and putting it back so many times. Looking at it, I think one pad is still in place on the board and the other pad pulled up with the capacitor but is still holding on to the board on one end and that is what is still holding the capacitor where I found it. Could I just solder it to pins 2 & 3 of U4? I'm going to check the connections of pins 2 & 3 just to be sure they are still connected to the things they are supposed to be connected to.
Edit: I just probed...Last edited by TopPop; 02-26-2023, 04:54 PM.Leave a comment:
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Re: Dell Precision M3800 won't turn on
I was probing around QV29 and QV30 and saw a messed up capacitor nearby. See attached photo. It is CT44....Leave a comment:
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Re: Dell Precision M3800 won't turn on
I put the motherboard back and reconnected everything except the battery. I see no graphics and no backlight. I press the power button, the light in the button comes on for about 4 seconds, and then it switches off. I've just been watching some videos and Googling some stuff. I guess the super IO chip is going through its component checks and finding something isn't good to go and switching off. I was looking at page 62 of the schematic specifically [AC in] 8th line down PBTN_SW# ...... 1ns < Tg < 4s Am I correct in thinking that everything...Leave a comment:
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Re: Dell Precision M3800 won't turn on
PU200
REGN is 6V
ACOK is 3.3V
ACDRV is 25VLeave a comment:
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Re: Dell Precision M3800 won't turn on
I replaced PQ200. Now the laptop will turn on, shows a power button light, then turns itself off after about 4 seconds. So, some progress was made but there is still something wrong with it.Last edited by TopPop; 02-25-2023, 06:20 PM.Leave a comment:
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Re: Dell Precision M3800 won't turn on
I figured the left sided 1 basically meant OL.
Right, PQ201 sort of is shorted but the short isn't in PQ201. The source to gate short is most likely in PQ200 and I'd have to separate them to be able to check for sure.
PQ200
source (1-2-3) & drain (5-6-7-8) mm set at 200, 0.5
source (1-2-3) & gate (4) mm set at 200, 1.1
gate (4) & drain (5-6-7-8) mm set at 200, 1.3
The drain of PQ201 is not shorted to ground but it would have been if I hadn't replaced PC205 earlier as...Last edited by TopPop; 02-20-2023, 12:53 AM.Leave a comment:
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Re: Dell Precision M3800 won't turn on
@mon2, yes that'd be great if you could recommend a substitute mosfet. I tried looking at the datasheet for the mosfet that is on the board but wasn't sure what specs were important to match and what were OK to have a bit different.Leave a comment:
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Re: Dell Precision M3800 won't turn on
I had a whole thing typed out and lost it to a request to log in. So here's the abbreviated version. I've probably been typing too much anyway.
PQ201
source (1-2-3) & drain (5-6-7-8) mm set at 2000M, 12
source (1-2-3) & gate (4) mm set at 200, 1.3
gate (4) & drain (5-6-7-8) mm set at 2000M, 12
I tried the 20M and lower ranges but got nothing.
Attached is a pic of the multimeter in case that helps inform every one of what I'm working with. I don't trust the...Leave a comment:
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