N3251w red light only no image

[mmoore5553]

I got this monitor / LCd for free. It has an issue though. I have attached pictures. I have 81.4 volts on d8. I checked zd4 and it shows 704 with diode check. So i assume that is right as i checked other zenor diodes and shows the same. I then checked q7 and appears fine. I could not see any caps that are bubbled . Where do i go next ?

I have a multimeter and ready to use it. I turn it on and it just shows a red light. All the caps look good.

[Agent24]

Re: N3251w red light only no image

I see one bulging capacitor. If the rest are the same brand they're probably all bad. Check\replace at least all the output capacitors.

[mmoore5553]

Re: N3251w red light only no image

I seen that and did not know if it was budged or not. I can not even read what type of cap it is.

[Fubar701]

Re: N3251w red light only no image

Sorry to barge, trying to start a thread but it doesnt allow me to, seeing if I can even comment

[Agent24]

Re: N3251w red light only no image

I seen that and did not know if it was budged or not. I can not even read what type of cap it is.

Desolder it and then read what it says. You'll have to anyway to replace it.

[mmoore5553]

Re: N3251w red light only no image

I just order a kit with all of the caps in them. As you said i will have to replace them anyways.


http://www.ebay.com/itm/230738469284

[Agent24]

Re: N3251w red light only no image

That'll work too

Just something to bear in mind in future, while that seller looks OK, and he says he uses good quality capacitors, some eBay sellers do not, or may use fakes (knowingly or unknowingly).

[budm]

Re: N3251w red light only no image

He is good, he is a friend of mine that I help out getting the good caps for the kits when he started the business.

[mmoore5553]

Re: N3251w red light only no image

That is good to know Budm. Nice to see you around. Well i finally got the caps but took awhile. I replaced just that one as it looked buggered. I still have a red light and nothing on the screen. I do not here the transformer or anything trying to kick on. Not sure where to look at this point.

I am open to ideas.

Should i go ahead and replace the other caps then ?

[mmoore5553]

Re: N3251w red light only no image

I did find this on the web but I am confused on what to look for.

[mmoore5553]

Re: N3251w red light only no image

Also found this

[Agent24]

Re: N3251w red light only no image

Do the whole kit and replace the lot, if one was visibly failed the rest are likely in bad condition even without visible signs of failure. If you don't have an ESR meter then you should just replace the lot. If it still doesn't work you can at least start troubleshooting knowing the capacitors are OK.

[mmoore5553]

Re: N3251w red light only no image

I have replaced all Caps and still in the same boat. Just red light when I plug it in.

[mmoore5553]

Re: N3251w red light only no image

Just wondering if anyone has any ideas what to check next. Thanks.

[Agent24]

Re: N3251w red light only no image

As this PSU seems to have APFC I think you can try budm's trick of checking voltage on the main filter capacitor.

Measure the voltage across this capacitor and then press the power button. If the voltage increases you know at least that the startup signal is getting through to the PSU and that the PFC circuit is working.

Post the voltages you get before and when pressing the button.

Be careful when doing this, since you're working on the hot side of the PSU which is connected to the mains. If you have alligator clips for your test leads, use them.

You should also probably check the 5v Standby rail to make sure it is actually supplying 5v.

[mmoore5553]

Re: N3251w red light only no image

I wish i had alligator clips for my multimeter. I will just use the leads. I assume you are talking about the big blue capacitor ? I was looking for the 5v standby and not sure where that is at on this board. Any advice ?

[Agent24]

Re: N3251w red light only no image

Yes the big blue one lying on its side. The main filter cap is almost always the biggest one on the board, closest to where the mains supply comes in.

Do the output connectors on the board have any markings next to them that might indicate which pins are for which voltages?

[mmoore5553]

Re: N3251w red light only no image

I do not see any voltages listed at all yet. I do have 167 volts across the cap. I can not hit the button to turn it on. I plugin the power cord and tv goes directly to red light. I can not hit the button while it is laying down and me trying to hold leads on it.

[mmoore5553]

Re: N3251w red light only no image

Closer inspection I see it looks like these too are burnt ? It tests fine but not too sure. What do you all think

[Agent24]

Re: N3251w red light only no image

Yeah those look bad alright. Q4 definitely and maybe D7 as well.

Are you testing in-circuit? That is unlikely to give correct results. Desolder and test both out of circuit, likely they have both gone open circuit.

167 volts while in standby sounds OK.