Samsung LN32b460 No Backlights...have sound and picture

[allsmith]

Re: Samsung LN32b460 No Backlights...have sound and picture

Btw, you need to remove the inline Lamp or use 200W lamp, at only 130V at the two legs of the cap when TV is on the PFC may not start up due to low Voltage lock out.
BTW, how about D804, 805, 810? you did show the test result of all 3 diodes.

Thanks Bud..
I have removed the dim bulb tester.
Sorry i should have posted results for dp810 and dp804 and dp805
dp810=fwd .48 rev= open
dp804=fwd .49 rev=open
dp805=fwd .40 rev=open

And yes i was using chassis as ground to check VCC on the PFC controller,sorry i didnt know.

The results of using the negative leg of the filter cap as ground has me showing basically 0v on the the VCC of the PFC controller .003v to be exact

[allsmith]

Re: Samsung LN32b460 No Backlights...have sound and picture

Ok guys i just caught a huge mistake on my part! So sorry!

I have been trying to test VCC on UM801S (ICE3BR0665J) thats on top of the board and not
UP801S (FAN7530) that i was supossed to. Dang i'm going to have you guys all messed up! so sorry! No wonder the datasheet for (ICE3BR0665J) didn't match
(FAN7530) on the schematic.

Ok so know my question is can i have the board out of the tv with the connections that go to the backlight not connected and power up the board upside down so i can test VCC on (FAN7530)?

Will powering up without those connections to the backlights damage anything?

So Sorry for my mistake!

[allsmith]

Re: Samsung LN32b460 No Backlights...have sound and picture

I believe i'm testing the right part now guys,sorry my bad.. Ok im testing
UP801S (FAN7530) PFC controller on the underside of the board..

TV on with power board upside down and hooked up to mainboard.

Grounding DMM to negative side of large filter cap

Testing VCC on pin 8 of UP801S (FAN7530) PFC controller i get 13.3vdc

What do you guys make of that?.. Could UP801S (FAN7530) be bad?

Thanks guys

[allsmith]

Re: Samsung LN32b460 No Backlights...have sound and picture

I'm lost without you guys..Im getting 13.3VDC on VCC (FAN7530) PFC controller.
Any other tests i can do?

I do have another (FAN7530) out of a parts tv that should be good (tv had a cracked screen)..I have been practicing with a hot air station on some junk boards and i think i could do the transplant,but rather not if i dont have to, but im ready to do it if it comes down to that...I dont have any solder paste ,but i've succeeded doing the soldering with the small chisel tip on my weller solder station

What are your guys thought?..I really appreciate the help

[allsmith]

Re: Samsung LN32b460 No Backlights...have sound and picture

Well guys i put a used Fan7530 in my board and now im back to a direct short as soon as i plug in the power cord,60 watt light bulb glows brightly!..

I doubled and triple checked for solder bridges with 15x loop and even R&I Fan7530 twice to make sure...

With Fan7530 REMOVED and board plugged in i have NO short.

My inexperienced tv mind can only think of a few things...
1...i got Fan7530 too hot with the hot air station removing it and fried it.
Or
2...now that i got a good Fan7530 in there something else is shorted.
Or
3...I did have a section of the board top layer and traces lift from heat next to Fan7530 when i was removing it, but it went back down after it cooled....Really my first time using a hot air station and of course i removed about 10 similar Fan7530 sized ic's from a cheap dvd home theater board without any board bubbling problems when i was practicing!! Go figure!

So really all i know to do is...
1..get a NEW Fan7530 and try it.
OR
2..put back in my old Fan7530 and see if i still have a short
Or
3..Put the used Fan7530 back into the parts board and see if it still works(parts tv worked but had cracked screen.

Thats all i can really think to do..

Any suggestions guys,... Before i write this one off...

I cant even find a replacement board for sale,..everywhere says out of stock..One or two sites had them for $100 but aint no way i'd spend that for one!!..SJ when they had them in stock were $60 or so,even then i dont know if it would be worth it for a little 32'' tv!...well maybe but no more than 60!..i would rather go about 40-50... i suppose that would be worth it..

My inexperienced mind can think of one more question for your experienced minds..

Would you guys know of a substitute board that is available?, or how to determine if a similar board in stock could or could not be used?

[CapLeaker]

Re: Samsung LN32b460 No Backlights...have sound and picture

Check the mosfet that is with the fan7530 if it is shorted. There is a possibility, that the fan7530 is bad and actually holds the mosfet on all the time. The fuse can only blow if there is something major shorted in the primary rail. So how do you figure, that you have a short? Do you go by the dim bulb tester, or do you actually measure a short with the DMM?

[allsmith]

Re: Samsung LN32b460 No Backlights...have sound and picture

Check the mosfet that is with the fan7530 if it is shorted. There is a possibility, that the fan7530 is bad and actually holds the mosfet on all the time. The fuse can only blow if there is something major shorted in the primary rail. So how do you figure, that you have a short? Do you go by the dim bulb tester, or do you actually measure a short with the DMM?

Just using Dim bulb tester...60 watt bulb glows full bright as soon as i plug in.
Bulb does not glow at all with Fan7530 removed.
Before i put in Fan7530 tv worked with no shorts,just no PFC ramp up

[allsmith]

Re: Samsung LN32b460 No Backlights...have sound and picture

i just pulled the mosfet and all combinations are open except .49v (diode test) between source and drain the one direction.

In circuit the mosfet had a reading in both directions from source and gate.. other combinations seemed normal

I cant remember how that mosfet tested in circuit before back when i didnt have a short.

[CapLeaker]

Re: Samsung LN32b460 No Backlights...have sound and picture

Your Mosfet is good. Unplug the PSU, make sure the main filter cap isn't charged, then see if there is a dead short on it, or check the bridge rectifier. If no dead short is there, check all the diodes for good measure. If one reads funny in circuit, take it out or lift a leg and measure it again. If you find nothing again, remove the dim bulb tester from the PSU and plug it in straight to the outlet. Either it works, or you will find out soon what part is / was bad.

[allsmith]

Re: Samsung LN32b460 No Backlights...have sound and picture

Your Mosfet is good. Unplug the PSU, make sure the main filter cap isn't charged, then see if there is a dead short on it, or check the bridge rectifier. If no dead short is there, check all the diodes for good measure. If one reads funny in circuit, take it out or lift a leg and measure it again. If you find nothing again, remove the dim bulb tester from the PSU and plug it in straight to the outlet. Either it works, or you will find out soon what part is / was bad.

Ahh...i see what your saying...maybe there is no short and the tv is trying to start up with the backlights now, and since i only have a 60 watt bulb in the dim bulb tester thats why it glowed so bright...i only plugged it in for a second a couple times,quickly unplugged...

Thing i noticed before but failed to mention is the tv seems to turn on as soon as i plug it in,which doesn't seem right to me,but if thats what its doing than yeah the dim bulb would glow bright if tv is pulling its full amps now..

Let me put the mosfet back in and give it a go without the dimbulb.

When you say test for a dead short on the large filter cap,...would that be checking between its leads?

[cliff_hootarski]

Re: Samsung LN32b460 No Backlights...have sound and picture

+ lead to - lead on the cap. If it shows steady low resistance, you have a short to ground.
UNPLUG your TV and ensure the Cap is COMPLETELY discharged before you attempt this.

[allsmith]

Re: Samsung LN32b460 No Backlights...have sound and picture

+ lead to - lead on the cap. If it shows steady low resistance, you have a short to ground.
UNPLUG your TV and ensure the Cap is COMPLETELY discharged before you attempt this.

thank you!..Im getting about 18 ohms on the leads of the cap...Mosfet is still removed..I will put it in now and retest the cap

[allsmith]

Re: Samsung LN32b460 No Backlights...have sound and picture

We have lift off!!! Heck yeah!!.. I removed the dim bulb tester and the backlights are on and working!!... Thanks so much guys!!..

I only left it on few a few seconds,because of that under rated mosfet i have in there...not sure if i should leave the tv on very long until i order and get the correct mosfet installed..but yeah its working!!

Thanks Capleaker!... i didnt think about the the 60 watt dim bulb glowing bright because the tv is now pulling its full amps to start up the backlights.

Dang there's a lot to learn about this stuff!.. And without your guys guidance i would have gotten nowhere!..Thanks everyone that has helped me!!

[CapLeaker]

Re: Samsung LN32b460 No Backlights...have sound and picture

We have lift off!!! Heck yeah!!.. I removed the dim bulb tester and the backlights are on and working!!... Thanks so much guys!!..

I only left it on few a few seconds,because of that under rated mosfet i have in there...not sure if i should leave the tv on very long until i order and get the correct mosfet installed..but yeah its working!!

Thanks Capleaker!... i didnt think about the the 60 watt dim bulb glowing bright because the tv is now pulling its full amps to start up the backlights.

Dang there's a lot to learn about this stuff!.. And without your guys guidance i would have gotten nowhere!..Thanks everyone that has helped me!!

Yeah, when I started out many moons ago, I fell for that exact same thing too. Next time you know better, same as I did.

[allsmith]

Re: Samsung LN32b460 No Backlights...have sound and picture

Im wanting to order a replacement mosfet this week and im not really finding one
(k10a60d) at digikey or mouser..Digikey shows it but out of stock..But they show a couple mosfets on the page that state ''customers of k10a60d may also be interested in''...Is that a digikey way of showing a equivalent part?
There showing a TK10a60E that looks to have all exact specs except input capacitance and gate charge that i have no clue about.Does TK10a60e look like a good equivalent? thanks guys..
http://www.digikey.com/product-searc...ywords=k10a60d