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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Dell W3000 Problem with Power Supply
I thought I had repaired this Dell W3000's power supply , but
after about 20-30 minutes the power light goes out (no video or audio) and the power light comes back on (sound and video returns for a sec.). IOW, the power goes off and then back on. Over and over again with a few seconds in between. All the voltages appear to be correct. I'm just not sure if it's the power supply or logic board. I replaced the bridge Rect.(it was shorted), 20N60 Transistor (shorted), Controller IC (shorted). and a couple of Schottky Diodes. This could be heat related. Any help or direction on this would great!!!! TIA |
#2
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Dell W3000 Problem with Power Supply
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#3
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Dell W3000 Problem with Power Supply
The primary side controller is a MC33262PG. Switching MOSFET: 20N60S5 The secondary schottky diodes (2): DSSK60-018A 180v 2X30A (I used two DSSK60-015A 150v 2 x30A) I could not find the exact replacement in stock. One other schottky diode in secondary: 20CTQ150PBF (I ordered it but did not replace it because it was not shorted) Bridge Rect.: D5SBA80-7000 6A 800v (I used a D5SBA60 6A 600v) At the time I ordered it, I could not find the exact replacement in stock. I guess that could be part of the problem, but the replacements are very close. As you know, parts are hard to find. Thanks for you help! |
#4
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Dell W3000 Problem with Power Supply
On Mon, 11 Aug 2008 14:46:34 GMT, put finger to
keyboard and composed: The primary side controller is a MC33262PG. That's a power factor correction controller: http://www.onsemi.com/pub_link/Collateral/MC34262-D.PDF There must be an additional PWM circuit to drive the chopper transistor for the switchmode transformer. Switching MOSFET: 20N60S5 The secondary schottky diodes (2): DSSK60-018A 180v 2X30A ... Could it be that an excessive load on this particular rail is the root cause of your problem? - Franc Zabkar -- Please remove one 'i' from my address when replying by email. |
#5
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Dell W3000 Problem with Power Supply
It also uses a least one ICE2AS01 controller IC.
It may have more, but I don't remember right off. |
#6
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Dell W3000 Problem with Power Supply
On Wed, 13 Aug 2008 14:59:06 GMT, put finger to
keyboard and composed: It also uses a least one ICE2AS01 controller IC. It may have more, but I don't remember right off. That IC has its own internal overload protection but no external on/off control. I was wondering whether the PSU had some control pin that was being triggered by a fault condition on the logic board. I notice that a lot of people are having power-up problems with your particular model. One vendor is offering a replacement logic board as a solution. Here is the datasheet for the PWM controller IC: http://datasheet.digchip.com/216/216...0-ICE2AS01.pdf - Franc Zabkar -- Please remove one 'i' from my address when replying by email. |
#7
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Dell W3000 Problem with Power Supply
This unit does have powering on issues.
Can you tell me which vendor is offering a replacement? Thanks |
#8
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Dell W3000 Problem with Power Supply
On Thu, 14 Aug 2008 03:51:35 GMT, put finger to
keyboard and composed: This unit does have powering on issues. Can you tell me which vendor is offering a replacement? Thanks This supplier is offering an exchange logic board for US$150: http://www.lcdrepair.us/w3000-logic.html The symptoms a Power, Sound But No Picture Have to press power button numerous times to get a picture Power, Picture But no Audio Output Not the same as yours, but it seems to be a common problem. I'd still be looking around the power supply area, though, before taking a chance on the logic board. If you do go for the board, I'd be keen to know what the fix is. The same supplier is also offering a PS for $120: http://www.lcdrepair.us/w3000-Power.html - Franc Zabkar -- Please remove one 'i' from my address when replying by email. |
#9
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Dell W3000 Problem with Power Supply
On Thu, 14 Aug 2008 17:01:00 +1000, Franc Zabkar
wrote: On Thu, 14 Aug 2008 03:51:35 GMT, put finger to keyboard and composed: This unit does have powering on issues. Can you tell me which vendor is offering a replacement? Thanks This supplier is offering an exchange logic board for US$150: http://www.lcdrepair.us/w3000-logic.html The symptoms a Power, Sound But No Picture Have to press power button numerous times to get a picture Power, Picture But no Audio Output Not the same as yours, but it seems to be a common problem. I'd still be looking around the power supply area, though, before taking a chance on the logic board. If you do go for the board, I'd be keen to know what the fix is. The same supplier is also offering a PS for $120: http://www.lcdrepair.us/w3000-Power.html - Franc Zabkar I have two W3000's and one of them has had the problem since day one. It usually comes on first try, but often requires two tries. On one occasion, it took 12 tries. Anyway, my guess (and I stress the word guess) is that the backlight takes about 5 or 6 seconds to fire and they have some logic that gives up if the backlight hasn't lit after a certain amount of time. Unfortunately, some backlights takes just about the same amount of time as the timer allows. If the timer expires before it lights, the logic gives up and turns it off. (Occasionally, it lights just as the logic turns it off so I see a flash of picture). In other words, the only real problem is the length of the timer. I have no idea if the timer is implemented in firmware of some sort but it is frustrating to know a simple change of a timer could fix the whole problem. My other W3000 (a year older and therefore a lot more expensive has never failed once.) The problem one was purchased "on sale" right before they stopped making them. Hmmm. ...Pat |
#10
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Dell W3000 Problem with Power Supply
On Thu, 14 Aug 2008 12:40:57 -0400, greenpjs put
finger to keyboard and composed: I have two W3000's and one of them has had the problem since day one. It usually comes on first try, but often requires two tries. On one occasion, it took 12 tries. Anyway, my guess (and I stress the word guess) is that the backlight takes about 5 or 6 seconds to fire and they have some logic that gives up if the backlight hasn't lit after a certain amount of time. Unfortunately, some backlights takes just about the same amount of time as the timer allows. If the timer expires before it lights, the logic gives up and turns it off. (Occasionally, it lights just as the logic turns it off so I see a flash of picture). In other words, the only real problem is the length of the timer. I have no idea if the timer is implemented in firmware of some sort but it is frustrating to know a simple change of a timer could fix the whole problem. My other W3000 (a year older and therefore a lot more expensive has never failed once.) The problem one was purchased "on sale" right before they stopped making them. Hmmm. ...Pat I notice that some (most?) lamp controller ICs have a timing capacitor that is set to charge up to some trigger point in one second or so. If the feedback voltage from the lamp's current sense resistor does not reach 3V within that time, then the lamp controller shuts down. I suspect that the "fix" in this case would be to increase the value of the timing cap. Having said that, I can't see how a logic board swap would cure such a problem, unless the uP was able to detect the lamp in some way. It may be worthwhile to identify the functions of the pins in the harness between the logic board and the inverter/PSU, or at least to identify the lamp controller chip and study the application circuit in its datasheet. - Franc Zabkar -- Please remove one 'i' from my address when replying by email. |
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