No Standby voltage 26" Sabre LCT260BKA

[XtraTN]

I have a 26" Sabre LCD TV. Once plugged in, the TV does not turn on at all. No response to the power button. The guy who gave it to me said it was just a fuse but I checked the fuse on near the AC input and it seems good.

Initial observations:

Opened it up, I found many bulging capacitors on the secondary side of the PSU. And I just replaced every capacitor as shown in the photo.

Once replaced I still have no change in the problem.
Checking across the biggest capacitor I have a reading of 162.5V

I'm checking voltages on components on the secondary side of the PSU but I measure almost all zero voltages.

There is no 5V standby voltage or any voltages on the outputs.

Looking for other fuses but dont seem to see any.

So what should I check next?

[budm]

Re: No Standby voltage 26" Sabre LCT260BKA

Did you replace the start-up caps in the primary side for the standby 5V power supply?

[XtraTN]

Re: No Standby voltage 26" Sabre LCT260BKA

Oh your right! I just checked the smaller caps you circled on the right with my esr meter The smallest one gave me a reading of greater than 40 ohms and the other cap was open circuit.

I thought the smaller caps usually rarely fail?

I'm pretty sure this TV was very heavily used though, the plastic for the connectors are starting to chip off due to heat wear. (Like when trying to remove ccfl lamps and the plastic piece easily snaps off with just a touch.)

[XtraTN]

Re: No Standby voltage 26" Sabre LCT260BKA

Success! I replaced those two other start up caps you suggested and now the TV turns on fine!

Just wondering does the voltage rating of the start up caps affect how long it takes the TV to turn on. For a minute I thought the TV wouldn't turn on but it just took awhile. Because I replaced the start up cap rated 100uf 35V with one that was rated 100uf 50V. The TV does take a couple of seconds for TV to come on after the red standby light turns green.

[budm]

Re: No Standby voltage 26" Sabre LCT260BKA

Great news, another trick I use for locating bad caps that have high ESR, use hair dryer. Check that bad cap when heated up and see if the ESR will go down. Hair dryer is one of my tools.
https://www.badcaps.net/forum/showth...312#post279312
If you will be working on a lot of TVs and monitors, these pictures may help you.
http://s807.photobucket.com/albums/yy352/budm/
By the way since that cap is for the 5V standby power supply, and the LED does change from red to green OK, so the 5v power supply is OK with the new cap, it does not have any affect on delayed on of the screen, that delay may be due to self test function of the TV when it turns on.

[XtraTN]

Re: No Standby voltage 26" Sabre LCT260BKA

I clicked your photobucket link but all I'm getting are photos of cats and dogs lol.

[budm]

Re: No Standby voltage 26" Sabre LCT260BKA

The right hand column for sub albums are the list of each brands.
For example, the SAMSUNG album:
http://s807.photobucket.com/albums/yy352/budm/SAMSUNG/

[XtraTN]

Re: No Standby voltage 26" Sabre LCT260BKA

Got it, Thanks!

[aris21067]

Re: No Standby voltage 26" Sabre LCT260BKA

my sabre lct260bka shows only a rapid red blinking light at the power button.
I have the same problem as the OP but instead on the large capacitor im showing only 70.1 - 72.7 volts, but it cycles extremely fast from 0-72v. I have replaced the same caps as the OP (the exact same ones he has circled in his pics) as well as replace the 3 startup caps as suggested. Still have a rapid red blinking light (no green, only red), Any suggestions? Thank you

[selldoor]

Re: No Standby voltage 26" Sabre LCT260BKA

There is something definitely not right with the voltage at the Big Cap.
Confirm that you did the test with meter on 600 vdc and you measured across the legs of the cap. IF you do it again to check take care as this is a HIGH Voltage area. Do not touch any heatsinks.


Welcome to the forum-
We can help a lot more if you please post good clear pictures of the whole chassis, and then pictures of each board, front and back (in the same orientation) and close up of connectors, (max resolution 2000x2000 and 2MB) using the manage attachments button, which is found by clicking "go advanced" under quick reply.

Please do not post inline and offsite as they slow down the loading of pages.

Examples of what is needed

https://www.badcaps.net/forum/attach...7&d=1280167246

https://www.badcaps.net/forum/attach...6&d=1280167246

https://www.badcaps.net/forum/attach...4&d=1280167246

It will be useful if you can say a bit about yourself - skills tools etc.

[aris21067]

Re: No Standby voltage 26" Sabre LCT260BKA

There is something definitely not right with the voltage at the Big Cap.
Confirm that you did the test with meter on 600 vdc and you measured across the legs of the cap. IF you do it again to check take care as this is a HIGH Voltage area. Do not touch any heatsinks.


Welcome to the forum-
We can help a lot more if you please post good clear pictures of the whole chassis, and then pictures of each board, front and back (in the same orientation) and close up of connectors, (max resolution 2000x2000 and 2MB) using the manage attachments button, which is found by clicking "go advanced" under quick reply.

Please do not post inline and offsite as they slow down the loading of pages.

Examples of what is needed

the attachments posted by XtraTN above shows the exact same power supply board that Im having issues with. The caps I had to replace are the exact same caps circled in those attachments.

The volt meter I used is: GB Instruments model: GCM-221 and it is an auto-ranging meter and max voltage is 600V. I can attempt to use a different volt meter if you need me to.

The LCD tv I have is a Sabre model LCT260BKA it is a 26" hd tv
the power supply board is a Megmeet MLT666 rev. 2.5
The large cap that was showing low voltage is rated 120uF, 450v, 105C

Skill level is pretty much novice but im learning by the minute, lol
I do know how to solder and desolder caps and have the tools to do so.
I replaced all the blown caps that had the tops bulging with matching voltage and uF rating.

ETA:
I just retested the large black cap (120uF, 450v, 105c) using a generic DT-830B digital multimeter thats rated for 750Vac. The voltage range I get now is 689-705 volts, way above the rated voltage for that cap. I think its possible that the DT-830B meter has a faulty reading.
ETA2: I also tested the cap with the auto range meter and it also showed the elevated voltage range (688-704). Now Im officially confused, lol
and again thank you for your help.

[selldoor]

Re: No Standby voltage 26" Sabre LCT260BKA

There is no point at all in our looking at other boards to try and spot something wrong with yours. The amusing anecdote we sometimes use is of the man who went to the doctors enquiring about a pain. The Doctor said
we will have to do an xray, and the patient said there is no need I have an xray here my brother had taken earlier.

Have you got your meters set on DC and are the leads plugged in correctly.
Are the batteries good. Set on ohms and touch the leads - should be nil
measure a 1.5v battery or two or your car battery just to test the meter/s.

[selldoor]

Re: No Standby voltage 26" Sabre LCT260BKA

The GCM221 does not appear to measure DC Voltage? Have you got the instructions?

Instructions for the DT830b

http://www.hobby-hour.com/electronic...multimeter.php

If it tests out ok use that one.

[aris21067]

Re: No Standby voltage 26" Sabre LCT260BKA

The GCM221 does not appear to measure DC Voltage? Have you got the instructions?

Instructions for the DT830b

http://www.hobby-hour.com/electronic...multimeter.php

If it tests out ok use that one.

youre correct, that tester dont test DC volts. Im sorry I have been testing the cap using AC (refer to the part where I said im a noob, lol). I will retest the cap using the DC setting and will test to verify the tester as well. thank you and again sorry about my noobishness.

ETA: Just tested the DT-830B multimeter and it does test DC and the battery appears to be good and testing a 1.5v battery showed a pretty acurate reading.

ETA2: retested the cap and its now showing a DC voltage range between 175-190.

[aris21067]

Re: No Standby voltage 26" Sabre LCT260BKA

There is no point at all in our looking at other boards to try and spot something wrong with yours. The amusing anecdote we sometimes use is of the man who went to the doctors enquiring about a pain. The Doctor said
we will have to do an xray, and the patient said there is no need I have an xray here my brother had taken earlier.

Have you got your meters set on DC and are the leads plugged in correctly.
Are the batteries good. Set on ohms and touch the leads - should be nil
measure a 1.5v battery or two or your car battery just to test the meter/s.

I will try to get a camera working so I can take pics of my board. but visually there are no blown caps.

[aris21067]

Re: No Standby voltage 26" Sabre LCT260BKA

Here are some pics of the PS board.










ETA: FYI, I removed one side of both heat sink cages for easier access.

[jetadm123]

Re: No Standby voltage 26" Sabre LCT260BKA

Your voltage across the main cap should read a steady 165-170VDC. Is the 175-190V you're seeing fluctuating? 190V seems awful high.

[aris21067]

Re: No Standby voltage 26" Sabre LCT260BKA

Your voltage across the main cap should read a steady 165-170VDC. Is the 175-190V you're seeing fluctuating? 190V seems awful high.

yes, its all over the board in that range. it changes voltage like every half second.

[selldoor]

Re: No Standby voltage 26" Sabre LCT260BKA

With your meter on 600vAC can you check your mains voltage where it comes into the machine - is that fluctuating.

[aris21067]

Re: No Standby voltage 26" Sabre LCT260BKA

the voltmeter shows the voltage at the end of the pig tail that plugs into the power supply board is stable in the range of 119-120 Vac. I left the tester leads connected to the pig tail for 1 minute to see if it would fluctuate.
I also set the meter to 1000VDC and retested the capacitor again, this time it shows 263-274 volts DC. (I know its blowing my mind as well.)