Samsung LE32R72B won't power up

[bigbrain]

Welcome everybody,
This is my first post.
Got a Samsung LE32R72B with a blinking red led. Won't power up. It as a psu BN-03775A rev1.3. Checked the 3 fuses and caps, all ok. In the hot side got 380 Vdc in CP812. At final conector to mainboard there no voltage at all, the 24v is missing to.
I apreciate any sugestions. (sorry my bad english)
Greetings!

[Kamikazi]

Re: Samsung LE32R72B won't power up

Hi,

I have a similar problem with the same TV which I inherited from a friend (red blinking light).

I had a look and one of the caps was obviously bad on the power board. I changed it with no success... I then changed all of the caps (except a 400v 150uf large cap) and still had no luck

I've been told it could be a problem with the main board but I don't see why I would have two problems on different boards...

Can anyone offer any suggestions on how to fix this?

[martyparish]

Re: Samsung LE32R72B won't power up

Pictures will be helpful.

@bigbrain did you test for ESR or just capacitance? ESR is a common failure and cannot be detected with standard DMM

@Kamikazi It's VERY possible that two boards can fail at same time! I know because my own TV had the power and main boards go at same time. You should start by confirming if there are any voltages at the connector that goes from PSU to main board. You want to at least see standby 5 volt.

Also: Be sure to read "LCD TV and Monitor basic troubleshooting guides" in the sticky section of this forum.

[Kamikazi]

Re: Samsung LE32R72B won't power up

I've attached a picture of the board for reference. The connector on the top right is the one that leads to the main board (ribbon has been disconnected in pic).

I'm getting 0.0.41 v on the +13 v pin to ground and 5.85 v on the PSON S/B (the second pin from the bottom) to ground... The 5 and 12 v read zero v.

Not sure if it is relevant but with no cable connected and listening closely I can hear a very faint and rapid repetitive clicking noise. When the ribbon to the main board is connected again the tone changes.

[Kamikazi]

Re: Samsung LE32R72B won't power up

Also, I've checked voltages on the left hand side of the board (24 v to grnd) and they cycle from about 3.4 - 5.5 v.

[Kamikazi]

Re: Samsung LE32R72B won't power up

I took the main board off to check the voltage regulators on the back as per this post:

https://www.badcaps.net/forum/showth...999#post300999

The first regulator was stable but out of tolerance (17-33 giving 3.26 when it should be 3.3v). There are 5 other regulators which do not hold stable voltages; they go up to their max voltage and then drop to zero in a cycle - I suspect this is related to the clicking / pulsing noise I mentioned in an earlier post?

Not sure where to go from here though!

[budm]

Re: Samsung LE32R72B won't power up

Disconnect the cable between the power supply and the inverter board to see if the 12/24V will come up to 12v, 24v. I have a feeling you have bad IC (the one in the middle with small heat sink) is bad. Right now the PFC/Voltage booster is OK because you are getting the 380V.

"3.26 when it should be 3.3v" that is OK, it is still within 2% (3.3 x 0.98 = 3.234v)

[tom66]

Re: Samsung LE32R72B won't power up

Schematic, in case it helps.
http://www.tgohome.com/ServiceManual...&Search=Submit

[budm]

Re: Samsung LE32R72B won't power up

You may want to read this thread regarding to that IC:
https://www.badcaps.net/forum/showth...ht=BN96-03775A

[Kamikazi]

Re: Samsung LE32R72B won't power up

Thanks for replies. I'll check the power when I get home... I'm not sure which IC you are referring to though?

[budm]

Re: Samsung LE32R72B won't power up

The one mouted on the small heatsink at the middle of the board as shown in your picture, please read the link I provided.

[Kamikazi]

Re: Samsung LE32R72B won't power up

When I disconnect the main board power connector I can find no voltage on the inverter side. When I plug it back in the voltages re-appear but cycle 3.5 - 5.5 v.

When I take both inverter and main board cables out I can find no voltages on either side (except for the 0.05 v on the +13 v pin to ground and 5.85 v on the PSON S/B to ground I mentioned earlier).

[budm]

Re: Samsung LE32R72B won't power up

You have to have the cable between the main board and the power supply board connected since the power supply needs the PS_ON and BL_ON from the main board to turn on the power supply and the inverter board. At this point you may want to look for the replacement power supply board, otherwise you will have to do component level troubleshooting of the power supply board.

[Kamikazi]

Re: Samsung LE32R72B won't power up

OK, thanks I'll see what I can find... In your opinion I would be best off just getting a new power supply board and not bother trying to replace the F9222L IC mentioned in the other post?

[budm]

Re: Samsung LE32R72B won't power up

You can try checking the DC voltage feeding the IC per schematic to see hwat you are getting at the IC's pins, but since the F9222L seems to be common failure which is more likely.

[Kamikazi]

Re: Samsung LE32R72B won't power up

I've ordered an F9222L IC, so I'll see how I get on and report back. Fingers crossed.

[Kamikazi]

Re: Samsung LE32R72B won't power up

Big thank you to all who helped. Changing the IC worked for me, I'm typing this on my now working tv

[budm]

Re: Samsung LE32R72B won't power up

Great job repairing it, thanks for the repair feedback.
By the way, how much was the IC?

[retiredcaps]

Re: Samsung LE32R72B won't power up

Lots on ebay in the $3 range + free shipping.

[Kamikazi]

Re: Samsung LE32R72B won't power up

I got two chips for £4 off eBay :-) total repair cost was ~£15 as I changed all the caps.