Samsung PS-50Q97HD powersupply problem

[PowerAmpFreak]

The standby supply operates fine and supply +5.1VDC.
The mainboard gives a PS_ON signal by remote, but nothing more happens. No PFC, VA or VS, no relays activating. Seems there is a problem with a main switched VCC or something.
A sticker on the PSU says: 50" PSPF531801A,
Wonder if it should be a +12V also from standby supply in psu connector CN801? PSU schematics is appreciated if anyone has.

[psmedley]

Re: Samsung PS-50Q97HD powersupply problem

I posted a link to the schematic in https://www.badcaps.net/forum/showpo...9&postcount=53

[PowerAmpFreak]

Re: Samsung PS-50Q97HD powersupply problem

Great, psmedley! Thanks a lot.

[mjharrisuk]

Re: Samsung PS-50Q97HD powersupply problem

Power Circuit Board Type BN44-0162A
Problem with Relay Clicking and Cycling On/Off occurs after 5 Minute warm up and normal TV operation. Problem has been proven to still occur with Xsus & Ysus PCB Board Plugs disconnected from Power Board.

In an attempt to resolve problem the following has been carried out:-
1) Replacement of bulging CapXon Capacitors with new Panasonic type of equivalent values on Power Board
2) Replacement of FETs QS801/QS802 & QX801/QX802 on Power Board

On initial powering up the following values were measured:-
1) Fuse 801S = 228Volts AC
2) Vs Test Point = 207Volts DC
3) Va Test Point = 63 Volts DC
4) Ve Test Point =15.1 Volts DC
5) 5.3V Test Point = 5.21Volts DC
6) VAC_A & VAC_B Output atBD801S/BD802S Rectifiers (Sheet 2) = 212Volts DC
7) Between PFC_OUT_DC400V_A and VAC_B (Sheet 1) = 400Volts DC (note! On removing the AC power supply the 400Volts DC takes approx 1 Minute to discharge which indicates the Large Capacitors CP802/CP803 are functioning satisfactory)

It appears that the Relay RL802S which supplies the AC onto the Rectifiers BD801S/BD802S is the clicking relay. This appears to be controlled by the VCC supply (Sheet 2).

I have attached a schematic diagram of the BN44-0162A PCB. Can anyone advise me how to proceed to test and find the component that is causing the problem with the intermittent VCC supply? Any help or assistance greatly appreciated.

[dick_barton]

Re: Samsung PS-50Q97HD powersupply problem

How do the voltages compare to the voltages as given on the panel label ?

[mjharrisuk]

Re: Samsung PS-50Q97HD powersupply problem

The Voltages all match the labels on initial powering up. After the 5 minutes of warm up the Relay starts clicking and seems to loop on/off in approx 15 second periods. With the Relay clicking the voltages applied to the Rectifiers is being switched on/off so the whole circuit supply is being affected. Initially I narrowed the problem down to the Power Board by disconnecting the X & Y Boards and the clicking still existed. I noticed two bulging capacitors on the Power Board. After reading that the CapXon capacitors did not have a very good name when I read posts on the forum I decided to change every Capacitor on the Board except for the 3 very large ones. 2 of those large ones for the 400VDC have been seen to be working fine by seeing the discharge slowly occur when AC power is removed. With all available Capacitors changed I then decided to fit new FETs on the Power Board as again these were mentioned as being the culprit in the forum. Alas the problem still exists! As the Clicking Relay is the one controlled by the VCC point (Sheet 2 of the Schematic) I am of the conclusion that the problem lies within one of the parts associated with that part of the circuit. I was condidering disabling the relay and shorting out the contact but I would much rather resolve the problem which would give me much more satisfaction.

[maxvalutech]

Re: Samsung PS-50Q97HD powersupply problem

You may need to consider main board and run voltage tests with it disconnected from powerboard and with jumpers for pson to gnd and vson to 5v at connector main board end. Is Ve only 16v. ??

[mjharrisuk]

Re: Samsung PS-50Q97HD powersupply problem

What I believed to read Ve was actually Vg on the Power Board. I have rechecked Ve on the X Board and it is 94.1VDC (pic 1427). Vg on the Power Board is measuring at 15.1VDC (pic 1426).

[flocko]

Re: Samsung PS-50Q97HD powersupply problem

Do a stand alone test on the power board ,remove all plugs from board leaving just the AC mains plug in, find PSon pin and ground it(relay should click and hold in all the time PSon is grounded) check all low voltages. if correct then with a 470-1k resistor jump VSon to 5v stby to bring up high VS voltage. if the power board tests is ok the problem is with the main board for PS.on or the logic board for VS on signals not being held on

[mjharrisuk]

Re: Samsung PS-50Q97HD powersupply problem

Thanks for the direction flocko

OK removing all plugs except the AC supply and grounding the PSon pin does cause a relay to click and become held on. With that carried out, checking all the voltages in the same positions that i originally listed I get the same values on all positions except there is now the loss of voltage on the Vs Test Point.
When I apply a resistor across VSon and the Stby connection VS is elevated to 207VDC. Leaving the connection applied over a period of time there has been no clicking of the Relay. I assume this points to the problem to being developed via the Main Board. Anything I can do to narrow the source of the problem down?

[mjharrisuk]

Re: Samsung PS-50Q97HD powersupply problem

Installing the plug back into CN801 Socket while leaving the resistor in place and applying the AC causes the intermittent clicking of the relay to commence again.

[flocko]

Re: Samsung PS-50Q97HD powersupply problem

CN801 is the supply and return plug to the main board. to confirm a main board fault remove this plug (CN801) and replug all others that have been removed, also remove the resistor jumping VS on. you will need to ground PSon to get the power board to come on, you will find on the logic control board pins marked 1/2/3 and 4 (please look up running Samsung test patterns in search , to save me typing it all out )

[syaoran123]

Re: Samsung PS-50Q97HD powersupply problem

Sounds like a cracked soldering issue to me. Im assuming you freshly soldered the two small transistors on the thin middle heatsink. Check for soldering of the smd resistors around this area.

[flocko]

Re: Samsung PS-50Q97HD powersupply problem

The power board is working as it should , he has done a stand alone test, just waiting for him to do logic board test just to check it is only main board PSon signal at fault

[maxvalutech]

Re: Samsung PS-50Q97HD powersupply problem

My guess bad joint on mainboard

[mjharrisuk]

Re: Samsung PS-50Q97HD powersupply problem

I have exposed the logic control board and attached a picture. Could you confirm if it is the block of six pins at the bottom left or the five inline pins at the top left that are the ones to be used for the Test Patterns?. Incidently when I had the AC supply on with the PSon grounded and the resistor fitted onto VSon to Stby a single green LED was flashing on the logic board and two other LEDs were solidly illuminated.

[mjharrisuk]

Re: Samsung PS-50Q97HD powersupply problem

Upper 5 Left Pins are marked CN2008 and the lower 6 Left Pins are marked CN2010. I have tried searching for running the Test Pattern associated with this TV logic board. As far as I can see from other posts associated with other TV logic boards I need to short pins 3 and 4 and it allow it to run through the screens sequence. Is that correct?

[flocko]

Re: Samsung PS-50Q97HD powersupply problem

First it is not good practice to apply jumpers when the boards (logic/main ) are connected, this can damage them, so only do this when the boards are disconnected (or with the signal wires(PSon /VSon) from the board taken out of the plugs).The pins for this test are the ones marked 1-6 on the lower left hand.for the test you need to connect pins 3+4.

[mjharrisuk]

Re: Samsung PS-50Q97HD powersupply problem

OK flocko. Before I energise anything can I just confirm that I have all set up correctly. On the Main Power Board all Plugs/Sockets (except CN801 to the Main Board) are connected. On the logic board I have a link between pins 3&4. When I apply AC I will activate the relay by grounding PSon. Is that correct?

[mjharrisuk]

Re: Samsung PS-50Q97HD powersupply problem

Is anyone aware of where there is a description of what should occur, and in what sequence when running the Test Pattern scans on a Samsung Plasma?