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viewsonic 32in lcd tv power supply broken
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train123



Joined: 26 Jan 2010
Posts: 88
Location: Canada
PostPosted: Tue Jul 06, 2010 10:43 pm    Post subject: Reply with quote
train123 wrote:
I did some more work and found the 4.8 volt "on" signal from connector CNS1-pin 12 is zero but when I lift the jumper going to QS3 the 4.8 volts return. I couldn't find QS3 or QS1 shorted but I'm not really sure how that circuit works.
Does anyone know what part QS1 or QS3 are?
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Guest
PostPosted: Fri Jul 09, 2010 1:06 pm    Post subject: Reply with quote
Where are they on the board? I can't seem to find them
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Guest
PostPosted: Sat Jul 10, 2010 2:40 am    Post subject: Reply with quote
anyone with a spare n3250w chip? new or used. I dont know where to buy them...
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veikra



Joined: 10 Jul 2010
Posts: 2
PostPosted: Sat Jul 10, 2010 3:39 am    Post subject: Reply with quote
Anonymous wrote:
anyone with a spare n3250w chip? new or used. I dont know where to buy them...


I registered Smile
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twerq
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PostPosted: Mon Aug 09, 2010 4:15 am    Post subject: I repaired my N3250w thanks to JRnTX Reply with quote
Read through a lot of posts. Seems power problems with the N3250w is either Caps. or Q7 & ZD4 . I replaced all the caps, even the ones not bulging. Still no go. I replaced Q7 with a discrete (yes, full size) 2N2222 transistor. It can be done. You need good eyes, a steady hand and a pencil iron. Same with ZD4. Installed a regular full size version. My LCD has been working now for several weeks!
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me
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PostPosted: Thu Aug 12, 2010 2:29 am    Post subject: Re: I repaired my N3250w thanks to JRnTX Reply with quote
twerq wrote:
Read through a lot of posts. Seems power problems with the N3250w is either Caps. or Q7 & ZD4 . I replaced all the caps, even the ones not bulging. Still no go. I replaced Q7 with a discrete (yes, full size) 2N2222 transistor. It can be done. You need good eyes, a steady hand and a pencil iron. Same with ZD4. Installed a regular full size version. My LCD has been working now for several weeks!


There are not any TV repair shops anymore because of products like this set, I seen more complaints concerning this model than any I have ever seen.
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train123



Joined: 26 Jan 2010
Posts: 88
Location: Canada
PostPosted: Mon Aug 16, 2010 9:15 pm    Post subject: Re: I repaired my N3250w thanks to JRnTX Reply with quote
twerq wrote:
Read through a lot of posts. Seems power problems with the N3250w is either Caps. or Q7 & ZD4 . I replaced all the caps, even the ones not bulging. Still no go. I replaced Q7 with a discrete (yes, full size) 2N2222 transistor. It can be done. You need good eyes, a steady hand and a pencil iron. Same with ZD4. Installed a regular full size version. My LCD has been working now for several weeks!


You probably won't have any problems in the future. The discrete components have almost double the heat dissipation ability as the surface mount ones so they are not likely to fail again.
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sebxtreme
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PostPosted: Sat Sep 18, 2010 10:15 am    Post subject: Re: Repair tip for Viewsonic N3250W or N3235W power supply Reply with quote
JRnTX wrote:
I just repaired an FSP 212-3F01 power supply in a Viewsonic N3250W. I have seen the same power supply listed for the N3235W. This one was totally dead with no 5V standby present. The problem was a shorted internal voltage regulator made up of Q7 and ZD4. The Q7 is a SOT23 size device and appears to be too small and over heats in the design. In this case it shorted from the over heating and that caused ZD4 to fail and shut down a 15V bias supply on the power supply board. I replaced Q7 with a 2N4401 to give it more power capability. Any small NPN transistor with a 25V or higher Vce rating will probably work. ZD4 is a 15V zener diode. Note that there appear to be two or three power supplies used in these TVs. This fix may also apply to similar FSP power supplies such as the FSP 228 but that has not been verified.

thank you guys , now my lcd screen is aliveeeeeeeeeeeeeeeeeeeeeee
rally i wish to send many many thanks !
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sp33dy1983



Joined: 19 Sep 2010
Posts: 1
Location: Hell
PostPosted: Sun Sep 19, 2010 10:14 pm    Post subject: THANK YOU JTS1957 !!! Reply with quote
hi,
I just wanted to thank you for posting all the usefull info on Q7 for n3250.

I have a client bringing one over, so I did some research prior and you have the best info and solution for this "deffective" model series. If you don't mind, I may ask you for advice from time to time.

I'm still uncertified (enrolling soon for computer hardware engineer), but I started trying to repair electronics at the age of 8, now I'm 27... I have a natural talent in electronics and some experience to back it up, but sometimes it's difficult to know wich "dirrection" to look for. replacing capacitors on stuff is simple, but knowing the value of a transistor and determining if it's pnp or npn is not so simple.

I would greatly apreciate any asistance you can provide, when I need it.
please excuse my babaling, lol and thanks for your time and knowledge *bows down to greatness*
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some_guy
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PostPosted: Thu Oct 07, 2010 2:49 am    Post subject: Reply with quote
l3fty wrote:
Power-On.com has the FSP212-3F02 & includes the cable needed to replace the FSP212-3F01 for $49.

Being a guest I can't post a link.

Replacing the bad caps isn't a big deal, but considering the time and the possibility that you mat still have a bad diode. $50 sounds like a better option.

Not dissin all the tinkerers out there. By all means keep up the good work. Cool


Thanks.

I bought that supply and it fixed it. N3251w Symptom: no sign of power. By way, it was working and then it never turned on again. No smell of burn components.

For other considering this, this power supply fits perfectly as shipped. I ordered it Sunday and it shipped Monday.

For people who are not too electrical, like myself, getting to the power supply is a matter of removing a lot of screws. The hardest thing was prying the plastic cover off. I used two small flat screwdrivers. The plastic cover goes back very easily. Be careful pulling the connectors off. I didn't time it but I would say a little less than an hour.

This forum and thread is great - great to have such expertise solving this scenario of what could have been for me a 4 year TV throw away.
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