Samsung UA60H7000AW Power Supply

[LazyHorse]

Hi Team,

I have a 60" Samsung with (I think) a Broken power supply BN44-00716A.

Fully dis-connected from the TV, there is 0 VDC on STB (JP911)

I noted in another thread someone mentioning issues around the 6A01, CM803 and DM809

Here are my voltages on ICM801S
Pin DC AC
1 184 394
2 NC
3 0 0
4 0 0
5 0 0
6 6.7 0
7 0.3 0
8 0 0
9 0 0
10 10.3 0
11 0 0
12 0 0
13 NC
14 6.7 11.6
15 6.7 11.6
16 9.9 21.2


CM803 714 VAC on 1 pin 10VAC on other pin
DM809 10.4 VDC on 1 pin 0vdc on other pin


Looking for help on where to look next to find why no stand by voltage.
TIA

[dick_barton]

It looks like the IC has been replaced and those solder joints around the IC are not looking good. Pins 3 & 4 along with Pins 7 & 8 look as though there may be solder stuck between the pins. It could be the photo but I would check.

[dick_barton]

What dc voltage do you have when measuring across the two pins of CP806 or CP807

[R_J]

This is a always on power supply, so there is no separate standby voltage. ICM801S will operate in Burst mode, Have a look at CM803, does it look nice and square or does it look slightly bulged? if bulged it is likely bad (open) Looking at the ac voltages you are measuring on CM803, it could be open and not coupling the switching pulse to the transformer primary.

[LazyHorse]

Thanks for the responses so far.
I checked continuity between these pins (3,4) and (7,8) and they test open circuit. I have attached another pic from a USB microscope.
CP806 and 807 appear to be largish Electrolytic across the output of the rectifier - these give me 320 DC across these terminals also attached

Nothing should have been replaced or re soldered - it has never been in for service - the TV took a power surge or lightning strike a while back and just looking at it now. The surge took out heaps in the house - Gas central heating, Ethernet over power devices, 3 wireless access points.

CM803 Looks OK - Diode testing give 484mV in one direction, open circuit the other. Impedance changes depending on the setting on the MM - 20k ohm gives 14.7 k ohm in one direction and open in the other. 2k ohm is open circuit in both directions. The DCV across CM803 is ~30mV

Thanks again.

[dick_barton]

The first photo does indeed show a better picture of the IC that I mentioned earlier.

The second picture, and again it could just be the photo, looks like one of the transformer pins has cracked solder joint around it.

CM803 would need to be tested with a capacitance meter or ESR meter to establish it's quality. A meter set in ohms or diode mode can't test the capacitor.

[R_J]

Now with better information on when it quit, I suspect the ic could be damaged, The cap does look ok as they usually bulge but the only way to be sure is with a capacitor meter.
It's the main ic that needs to operate in burst mode to provide the standby voltage of around 8v. Without this standby voltage nothing else will work as this also supplies the vcc to the opto couplers, pfc vcc etc.

[LazyHorse]

Apologies for the delay in responding - I was waiting for some test equipment to be delivered.

I have tested CM803 out of circuit to 26.7 nF and ESR of 64.6 ohms - does that Sound OK?

[R_J]

Yes that cap checks ok, they usually go open when bad. Check that none of the diodes (DM851,2,3 & 4) are not shorted, But I suspect the ic, If it was working at all it should provide burst pulses to drive the two mosfets that drive the transformer primary, that should produce some voltage in the secondary, In standby it would be around 8vdc. There are a few small elec. caps in the circuit that you could check like CM809, (CM???, next to QM807)

[LazyHorse]

Thanks for the reply R_J;

I ordered and tried replacing ICM801S - but failed at soldering Pin 12 (GND) correctly. When I connected power The main fuse FP801S blew - so now I am waiting to try again. Those capacitors (CM814, CM809 and CP812) test OK (All sub 1 ohm ESR in circuit)
The forward voltage of DM851C & 2C is 120mV DM853C &4C is 380mV

I shall post again following the next test.

[LazyHorse]

Unfortunately the fuse has blown again. Is there a way to current limit the AC input to find what might be causing the fuse to blow?
I have ordered a new power board from TVPartsToday - hopefully they are a reputable company.

[neilc6]

I repaired a similar power supply with a blown fuse by replacing the two switching FETS. I think one was shorted. You should be able to measure the short with a multimeter on one side of the fuse to ground.

[LazyHorse]

Hey - I just wanted to say thanks for all the support received. I was not able to repair the board - but the replacement from TVpartstoday arrived on Wednesday, and I am up and running again.

FYI I check some more components on the board and found a short between the pins on QP802C (EYA7) - not sure why this didn't cause issues until I had replaced ICM801S.

Thanks again.

[R_J]

Is QP802C one of the fets that is driven by ICM801S? Did you check it before and it was ok?

[Davi.p]

Are you still interested in repair the board? OBVIOUSLY it is needed two pictures of front / back of entire board or schematic.