Dell ONE All In One Computer

[Rolin]

Hi guys, I have a Dell all in one Computer that has a power supply problem. I realize this isn't just a computer monitor, but it's not a laptop either so hopefully this post will fit here.

I've attached pictures. I checked a few components and eventually found the following problems: a blown fuse, faulty MOSFET 20N60C3 , faulty DIODE BYV29X-600. I labeled the diode and the mosfet on the heatsink where they attach (can't get pictures well in that area).

I contacted Digikey for the 20N60C3, and they didn't have it, so they crossed over to a 20N65C3. Once the parts arrived, I soldered on the the board and tested.

SPARKS! I quickly unplugged it! Tested the fuse - didn't blow. Noticed the area by a chip TNY277PN (see close up picture) is blown. There was a heatsink over this chip which I removed to inspect the damage. I suspect this chip is blown. Looked it up on Digikey and it states " IC OFFLINE SWIT OVP OTP HV 8DIP"

Heres my concerns: I'm hoping the substitute MOSFET that Digikey provided is OK. Again, original 20N60C3 to replacement 20N65C3. They sent me a nonisolated package, so I used a isolation kit I took off a junk board (insulation pad and nylon washer for the screw). But closer inspection of the BYV29X-600 DIODE shows there was a mistake. Somehow I was shipped a 568-7578-5ND, but I believe it should have been 568-9726-ND. Could either of these caused the sparks at the TNY277PN chip? And do you think I did further damage to the board beyond the TNY277PN? Hopefully I didn't completely kill the power supply because they're expensive and hard to find.

Hopefully someone can help and give me some good news!

Rolin

[Davi.p]

Re: Dell ONE All In One Computer

"IC OFFLINE SWIT OVP OTP HV 8DIP" is a strange description anyway it is surely the switching controller ic..
"Somehow I was shipped a 568-7578-5ND, but I believe it should have been 568-9726-ND"
What the hell of part number are theese?

[Rolin]

Re: Dell ONE All In One Computer

Sorry, I'll explain. The original Diode is BYV29X-600, digikey part number is 568-9726-ND. But somehow I received (or mistakenly ordered) 568-7578-5ND which is a BYV29FX-600. So these parts are similar, but certainly not the same.

I'm a novice, so I'm really not sure how badly it would affect the board. Sparks are no fun! Need to understand whether it was this Diode, or the substitute MOSFET, or something else!

Rolin

[Davi.p]

Re: Dell ONE All In One Computer

The parts are nearly the same and is not the problem, have you tested the pwm IC before installing/ordering the other parts? Usually when the main mosfet goes short it carries with it also the pwm ic and the usually big resistor of less than 1 ohm that comes from S pin of mosfet to GND.

[Lumberjack777]

Re: Dell ONE All In One Computer

Actually your thread belongs over in the "Power Supply Design and Troubleshooting" area.

This thread is for "Troubleshooting Computer Displays"

I will give you one word of advice though. By the time to buy all the parts that may have been blown with the "sparks". You might consider using that money towards buying a new power supply, or a used one.

[shovenose]

Re: Dell ONE All In One Computer

I would buy a working replacement psu keep the broken one try to fix it. Then you will have s spare or something to sell on eBay to make back some of the money you spent on the repair.

[Rolin]

Re: Dell ONE All In One Computer

Had to look up what a PWM IC is: Pulse Width Modulation. It appears the TNY277PN is a PWN IC.

So Davi.p, you believe the differences between 20N60C3 and 20N65C3 would not cause any issues. And you also believe BYV29X-600 and BYV29FX-600 is close enough not to cause the sparks (I'm interested in whether you think I could leave it in as a substitute or should I change it with the correct part).

No, I didn't check the TNY277PM before I replaced teh other components. So based on what you said it's possible the original faulty MOSFET damaged this PWM IC.

You mentioned a possible shorted resistor by the MOSFET - is it the one mounted vertically (under heatshrink) next to the 20N65C3? I removed and am trying to find the value. I must be color blind or something - the second band is either brown or green but it's hard to tell because the resistor is green. I believe it's Black/Brown/Gray/gold/Black. If that's correct, this should be 1.8 ohms. I tested it and it's shorted out no matter what the value is. Is this what caused the sparks!?!? I uploaded a pic to give your opinion on the value.

BTW: i pulled the plug immediately. The fuse did not blow - what are the chances I saved the board before something else blew?

Lumberjack - sorry about posting in the wrong area. As far as replacing the power supply? As I said it's rare and expensive - theres one on Ebay right now for over $200!! Great incentive to repair this one if I can - and I'll feel so proud!!

[budm]

Re: Dell ONE All In One Computer

TNY277PN is a PWM IC is for the standby power supply section. You have other PWM IC (SMD type) which drives the power MOSFET for the power supply section that is turn on by the signal from the main board. You also have PFC voltage booster circuit which also has power MOSFET driven by the PFC controller IC. Right now we do not know which circuit the blown power MOSFET is in.
As indicated, when MOSFET blown up, it will usually take out the Gate drive circuit and the IC that drives the Gate of the MOSFET with it.
We always suggest to replace the IC at the same time as the MOSFET, the components in the Gate drive circuit must also be checked for damaged so you will not blow up the new MOSFET.
I would also suggest that you get new power supply.
This is what I see from looking at the board.
Closed up pictures (both sides of the board) of where the MOSFET and the blown resistor are?
From your pictures, it looks like they are in the PFC circuit.

[Rolin]

Re: Dell ONE All In One Computer

Budm, appreciate the info. I wish I could get a good picture of the MOFSET area I replaced, but there is too much in the way. I noted the part numbers on the heatsink in the picture to help show where they came from. But I'll try to get a better picture tomorrow.

In the picture you edited to show the different areas of the board, I further edited it to show where the MOFSET, Diode and Resister. All located in the "PFC Voltage Booster" area. BTW: The Diode was a TO220 package.

Hopefully I can fix this one. It's a Dell One a2010 computer - power supply part number is GW715 - Computer is about 7+ years old. Right now there is a used power supply on ebay for $250, but I've seen them go for more and a little less - it's just too much money to put into an older computer. It's disappointing to hear the recommendations to purchase a replacement power supply.

Rolin

[Lumberjack777]

Re: Dell ONE All In One Computer

Hey Rolin. We probably should have gotten the issue with the exact type of power supply out of the way earlier. My apologies. Yes, it's proprietary and anybody that even pulls one to sell, gouges the price I see. ($200 - $300) You can buy a fully working used Dell A2010 for less! I hate proprietary parts in computers for just that reason.
From my experience, once it's had a major meltdown in that area. I replace all the parts I thought were bad, plug it in, and boom. Missed a small smd cap or resistor somewhere. There's a difference between component fault. And a circuit fault. Circuit faults are much harder to repair, because if you miss just one component, it will blow again. I noticed they also used that glue that appears to be dark brown. That is known to be conductive. In fact I wouldn't be surprised if that's what caused the problem to begin with.
I totally respect your eagerness to try and repair this. I'm the same way. And you have the BEST technical help in the world here such as budm. And I wish you the best if you decide to purchase all the components.
If you do decide to buy a power supply; I did manage to locate one for $145.
http://www.pinnaclemicro.com/compute...N2001A301&cf=5
That's refurbished which means they probably replaced the faulty parts.
If you end up buying one; make sure to remove that dark brown glue.
Good Luck Rolin.

[Rolin]

Re: Dell ONE All In One Computer

Budm, I uploaded a top picture of the MOSFET, diode and resistor area. I did the best I could - there isn't an easy way to take a picture - pretty tight in there. I labeled where they are though, so hopefully that will help.

Lumberjack, the computer is more like 5 years old rather than 7+ like I thought before. It's still a good computer, but certainly not worth much the way it is! I'm afraid your experience in fixing a "melted" power supply is what I feared - replacing parts only to find they blow again because you missed one small shorted component. Hopefully someone who is well experienced can help prevent that. Again, if this was a $50 power supply, I would just replace it - but this one is ridiculously priced.
BTW: I did some reading about the glue used in old electronics becoming conductive after years of thermal cycles - but from I read it affects equipment from the late 70's and 80's. According to what I read, it's very rare to see it in something manufactured recently. I could be wrong, it's just what I read. Thoughts?

Rolin

[budm]

Re: Dell ONE All In One Computer

OK, that is the MOSFET and Diode for the PFC. I cannot tell from the picture if that blown resistor is the fusible fuse for feeding b+ to the PFC or if it is the resistor for the Source pin of the MOSFET. We will need the P/N of that PFC Controller IC to see how the circuits are connected.
I also do not know why the SMPS IC for the standby power supply is also damaged, it is in different circuit.
I will also look at the CRC.ORG where I do my Saturday volunteer works to see if we have the power supply.
So it is the DELL A2010, and the power supply is GW715.

[Rolin]

Re: Dell ONE All In One Computer

The resistor in post #7 is the one pictured in post #11 (i quickly fitted back on the board for the picture). I made a mistake in my picture in #9 for the resistor location. I attached the corrected picture. the resistor connects to the 3rd pin of the 20N65C3.

You need the part number for the PFC Controller IC? Which component is the PFC IC?

I would be surprised if you have this power supply, but if you have one for a reasonable price, i would owe you many beers!

[budm]

Re: Dell ONE All In One Computer

U3 is the PFC Controller IC in that PFC section.

[Rolin]

Re: Dell ONE All In One Computer

SG6961SZ is the PFC - digikey sells them

That was tough reading - had to use a microscope!

[budm]

Re: Dell ONE All In One Computer

So if you look at the spec sheet, you will see the drive output pin that will be connected to the Gate of the MOSFET though the Gate drive network circuit, you must check out ALL those components closely for any damage.
So verify that the TO-220 Diode is also good. A lot of components in that PFC circuit will have to be checked.
So is that 0.18 Ohms resistor checked out open circuit? you have indicated as shorted out, more likely it is just real low Ohm resistor. It will go open if it is bad.

[Davi.p]

Re: Dell ONE All In One Computer

Hi Rolin, i'm sorry i don't had watched all your pictures and also with few attention, i agree with budm (exept the suggestion to giving up) also i tend to confirm that the diode you changed is equal/better than the original (faster), the mosfet i don't have watched its pdf but the name is pretty self explanatory, 20Amp 600v the original 20Amp 650/700V the one changed (maybe this has substituted the first in catalog), the resistor you showed has the center band silver not gray so it seems 0,08ohm, then probably is good not shorted, if the mosfet is gone short also the pfc ic probably does so i don't know if there's a way to test it, except with an oscilloscope and an external supply, now i'm watching pfc ic pdf, i've never had a pfc circuit by hands..

[budm]

Re: Dell ONE All In One Computer

SG6961SZ spec sheet.

If you want to check the IC, you can check the resistance reading between GD (PIN 7) and VCC (PIN 8). I would just replace it.
GD (PIN 7) and GND (PIN 6).
Also check the Diodes as you can see in the ref circuit fig 15, there are two Diode for the PFC D3, D4. You need to locate and check those two diodes that are connected in the same fashion as shown in the diagram. You already replace one which I am not sure how it is connected in the circuit.
Did the diode show up as shorted when measure off the board?
By the way, the TNY SMPS IC for the standby supplies the SWITHCED +VCC for running the PFC IC and the other SMPS IC.

[Davi.p]

Re: Dell ONE All In One Computer

He replaced the power diode, the one between Drain and + of bigger cap..
budm what you said here? i don't understand:
"By the way, the TNY SMPS IC for the standby supplies the SWITHCED +VCC for running the PFC IC and the other SMPS IC."
anyway to the OP you must check also the resistor between MOT and GND of the ic.

[Davi.p]

Re: Dell ONE All In One Computer

If the next attempt will fail i guess the pfc can be bypassed.. not?