Issue with Westinghouse 19" LCD Monitor (large pics)

[EGuevarae]

Re: Issue with Westinghouse 19" LCD Monitor (large pics)

Thanks for the info. You might be right. I called the company today and they were still out and did not know when they would be getting any in.

I did have another question.

Regarding the MOSFETS:
I could not find the "40T03GP" in mouser but i did find the following as a replacement. Is the following a good replacement?
NTP45N06LG (from ON semiconductor.....MOSFETs- Power and Small Signal 60V 45A N-Channel).

Dave

http://cgi.ebay.com/ws/eBayISAPI.dll...m=370166175275
That's where I got replacement MOSFETs for a unit just like mine. I don't know about the fuse, as now that I remember, it is still bridged with solder (something I have to take care of...)

[Welchs101]

Re: Issue with Westinghouse 19" LCD Monitor (large pics)

Ok, i have been working on this monitor off and on for some time now.

Where i am today:
The fuse F200 KEEPS blowing open when ever i try to turn on the monitor. I have trouble shooted as best i can but i am at a loss as to what to try next.

I thought about replacing the BIT3713 and someone was kind enough to find a location where i can buy a replacement but i recieved word back from the manufacturer that pin 13 might indeed be gnd so now i am thinking its not the BIT3713.

Since i cant buy a replacement board DAC-19M005 i am stuck trying to fix this board again. As i said above i am not sure what to do next. The only thing i can think of is shorting out the fuse F200 and touching components to see if they are hot.

Does anyone else have any ideas? Sorry to keep this thread going so long.

dave

[PlainBill]

Re: Issue with Westinghouse 19" LCD Monitor (large pics)

Ok, i have been working on this monitor off and on for some time now.

Where i am today:
The fuse F200 KEEPS blowing open when ever i try to turn on the monitor. I have trouble shooted as best i can but i am at a loss as to what to try next.

I thought about replacing the BIT3713 and someone was kind enough to find a location where i can buy a replacement but i recieved word back from the manufacturer that pin 13 might indeed be gnd so now i am thinking its not the BIT3713.

Since i cant buy a replacement board DAC-19M005 i am stuck trying to fix this board again. As i said above i am not sure what to do next. The only thing i can think of is shorting out the fuse F200 and touching components to see if they are hot.

Does anyone else have any ideas? Sorry to keep this thread going so long.

dave

Way back in the old days we would take a variable power supply, hook it up, then gradually increase the voltage until the current started to increase. If a 2Amp fuse was blowing, we'd raise the voltage until the current reached 2 amps, then Carefully!! feel for something getting warm.

Another 'trick' was to measure the voltage drop between the power supply and various components pulling power from the supply. The one causing the biggest drop was most likely to be bad. Of course, this was made easier by the fact we had complete schematics, an ample supply of components, and professional reworkers to install them.

PlainBill

[Welchs101]

Re: Issue with Westinghouse 19" LCD Monitor (large pics)

Plain Bill,

Thanks for the tip. Unfortunately i dont have a variable power supply but i still appreciate the tip.

Dave

[EGuevarae]

Re: Issue with Westinghouse 19" LCD Monitor (large pics)

First, install the caps in a more proper way. The long legs increase the ESR or so I've read around here. Have you removed the transformer to check if it is shorted?

[Welchs101]

Re: Issue with Westinghouse 19" LCD Monitor (large pics)

Hi, Thanks for responding.

I agree that i need to put the caps in "better" but how they are put in now should not cause a short. I put them in this way thinking it was temporary and once i found where the short was located i would put them in correctly.


Regarding the transformer.
Not sure if this is technically correct but this is how i tested the transformer.
Early on i did short out the fuse which keeps blowing and i placed one of the leads of my dvm over / on top of the transformer. With the dvm on frequence measurment i did record a frequency value from the transformer. I know this is not technically correct but i read this technique somewhere and i thought that if the transformer was shorted i would not read a frequency value.

Does this make sense?

Dave

[PlainBill]

Re: Issue with Westinghouse 19" LCD Monitor (large pics)

I've just received the Acer 19" version of this monitor. So far I've seen 2 bad (vented) caps, a shorted FET, and a blown fuse. Interestingly, my new esr meter says that one of the bad caps still has a low esr.

What is the value of F200. According to the only chart I could find, that is a 7 amp fuse?

PlainBill

[EGuevarae]

Re: Issue with Westinghouse 19" LCD Monitor (large pics)

I've just received the Acer 19" version of this monitor. So far I've seen 2 bad (vented) caps, a shorted FET, and a blown fuse. Interestingly, my new esr meter says that one of the bad caps still has a low esr.

What is the value of F200. According to the only chart I could find, that is a 7 amp fuse?

PlainBill

I've seen that unit too. It's an Acer AL1916W. Same PSU as the unit on this thread and on the L2046NV of a thread I opened. In my case, it was a blown fuse (F200) and two caps (see attached pic). The fuse was replaced by another "F200" from a dead (and almost empty) same model PSU, but I have no data on the fuse's specs.

[Krankshaft]

Re: Issue with Westinghouse 19" LCD Monitor (large pics)

Crapxon strikes again.

I'm seeing this more and more two of the inverter transformers in one assembly. As in the board pic above.

Is it cheaper to produce them that way or is it just quicker on the assembly line when inserting parts?

[PlainBill]

Re: Issue with Westinghouse 19" LCD Monitor (large pics)

Crapxon strikes again.

I'm seeing this more and more two of the inverter transformers in one assembly. As in the board pic above.

Is it cheaper to produce them that way or is it just quicker on the assembly line when inserting parts?

I'd say both. The downside is that you have a slightly higher chance of a manufacturing failure because of the extra winding.

Boy, that picture looks familiar!! Right down to the same two caps popping their tops.

Has anybody analyzed this circuit? Is this just a case of the caps failing, the high ripple causes the FETs to overheat, and when they short the fuse blows?

PlainBill

[EGuevarae]

Re: Issue with Westinghouse 19" LCD Monitor (large pics)

Is this just a case of the caps failing, the high ripple causes the FETs to overheat, and when they short the fuse blows?

PlainBill

A friend of my dad, who is an old school electronics tech, said that very same thing to me after seeing pics I sent him. The caps failure overheat/overwork the MOSFETs, and when they short, the fuse blows to protect the board from more damage.

[PlainBill]

Re: Issue with Westinghouse 19" LCD Monitor (large pics)

A friend of my dad, who is an old school electronics tech, said that very same thing to me after seeing pics I sent him. The caps failure overheat/overwork the MOSFETs, and when they short, the fuse blows to protect the board from more damage.

Thanks for the confirmation.

PlainBill

[jepongski]

Re: Issue with Westinghouse 19" LCD Monitor (large pics)

i have found something that might be useful about the "Fuse thing" . i dont know if this is the same as the "f200" we're talking..

the fuse labeled "M" or "W" is 5A.

[jepongski]

Re: Issue with Westinghouse 19" LCD Monitor (large pics)

i have overlooked the markings description "M' =4A.

[PlainBill]

Re: Issue with Westinghouse 19" LCD Monitor (large pics)

i have overlooked the markings description "M' =4A.

Hmm, note to PlainBill. " Chinese make M that looks like inverted W." 4 Amps is very reasonable; thank you very much.

PlainBill

[Dgtech]

Re: Issue with Westinghouse 19" LCD Monitor (large pics)

After viewing this thread plus one other thread on this site, I have concluded that there are too many of these same power supply failures. I bought a Westinghouse monitor cheap from craigslist and it had this failure. So far I've replaced about 9 caps(2 bulged), shorted out the fuse (F200 - on solder side of board), and I will change out the 2 mosfets as soon as they arrive. These posts have been great. Although I'd like to see a schematic of it all, It saved me tons of time researching the posts. I now know that this board is used in many models and brand names :

These are the ones that I know of so far...
Acer
ViewSonic
Westinghouse

No wonder why they want you to buy the extended warranties at electronics stores. The product manufacturers obviously buy the cheaper parts to sell to the customer. Some units last. The ones that dont last either get trashed or fixed by techs or in few cases, get sent back by way of the protection of the limited or extended warranty. In every case, the company makes tons of money!!!

[EGuevarae]

Re: Issue with Westinghouse 19" LCD Monitor (large pics)

After viewing this thread plus one other thread on this site, I have concluded that there are too many of these same power supply failures. I bought a Westinghouse monitor cheap from craigslist and it had this failure. So far I've replaced about 9 caps(2 bulged), shorted out the fuse (F200 - on solder side of board), and I will change out the 2 mosfets as soon as they arrive. These posts have been great. Although I'd like to see a schematic of it all, It saved me tons of time researching the posts. I now know that this board is used in many models and brand names :

These are the ones that I know of so far...
Acer
ViewSonic
Westinghouse

No wonder why they want you to buy the extended warranties at electronics stores. The product manufacturers obviously buy the cheaper parts to sell to the customer. Some units last. The ones that dont last either get trashed or fixed by techs or in few cases, get sent back by way of the protection of the limited or extended warranty. In every case, the company makes tons of money!!!

I've seen the same PSU/Inverter model in Acer and Westinghouse units personally. Bad MOSFETs, blown fuse on solder side and badcaps in all of them.

[bcuda]

Re: Issue with Westinghouse 19" LCD Monitor (large pics)

Hello,

I am new here and to repairing LCD's. I have tinkered with a lot of other things though. Great info here. Thanks in advance!!

I too have a Westinghouse L1975NW with no backlight. But mine has a different board that the original one in this thread. It has two dual Mosfets parts number P605. Also about half of the caps are Capxon and the other half are Taicon. Only 4 of the Capxon are bulged. Should I replace the Taicon caps also or are they okay? Where is the fuse on the solder side you guys are talking about? The main fuse is good as the LCD panel works. I'll replace the mosfet's along with the caps as they look pretty overheated.

I'll try to attach a couple of pics.

Thanks,

Bob

[EGuevarae]

Re: Issue with Westinghouse 19" LCD Monitor (large pics)

Hello,

I am new here and to repairing LCD's. I have tinkered with a lot of other things though. Great info here. Thanks in advance!!

I too have a Westinghouse L1975NW with no backlight. But mine has a different board that the original one in this thread. It has two dual Mosfets parts number P605. Also about half of the caps are Capxon and the other half are Taicon. Only 4 of the Capxon are bulged. Should I replace the Taicon caps also or are they okay? Where is the fuse on the solder side you guys are talking about? The main fuse is good as the LCD panel works. I'll replace the mosfet's along with the caps as they look pretty overheated.

I'll try to attach a couple of pics.

Thanks,

Bob

Welcome

Replace all the caps while you are there. For the fuse, post a bigger picture of the underside to see if we can see if any fuse is there.

[Nama]

Re: Issue with Westinghouse 19" LCD Monitor (large pics)

your board has crabs.