FP-29 Yaesu Switching Power Supply Problem

I will test the back lights first.

To test the back lights, you need to disconnect the cable between the main power supply & the main board, apply the AC power to the power supply, if the back lights are not light up, the back light are defective.

Pin Name Color
Description 1 3.3V Orange +3.3 VDC 2 3.3V Orange +3.3 VDC 3 COM Black Ground 4 5V Red +5 VDC 5 COM Black Ground 6 5V Red +5 VDC 7 COM Black Ground 8 PWR_OK Gray Power Ok is a status signal generated by the power supply to notify the computer that the DC operating voltages are within the ranges required for proper computer operation (+5 VDC when power is Ok) 9 5VSB Purple +5 VDC Standby Voltage (max 10mA, max 2A in ATX 2.2 spec) 10 12V Yellow +12 VDC 11 12V Yellow +12 VDC 12 3.3V Orange +3.3 VDC 13 3.3V Orange +3.3 VDC. ATX V2.3 / EPS12V V2.92 both define that the PSU has to use remote sensing to compensate cable drops on the 3.3V line. Because of this there is an additional brown cable crimped together with the orange cable either to pin 13 (ATX) or pin 1 (EPS12V). 14 -12V Blue -12 VDC 15 COM Black Ground 16 /PS_ON Green Power Supply On (active low). Short this pin to GND to switch power supply ON, disconnect from GND to switch OFF. 17 COM Black Ground 18 COM Black Ground 19 COM Black Ground 20 -5V White -5 VDC (this is optional on newer ATX-2 supplies, it is for use with older AT class expansion cards and can be omitted on newer units) 21 +5V Red +5 VDC 22 +5V Red +5 VDC 23 +5V Red +5 VDC 24 COM Black Ground /PSON activated by pressing and releasing the power button while the power supply is in standby mode. Activating /PSON connects the power supply's /PSON input to ground, thereby switching the power supply to full-on condition.

A switching regulator is a bit of electronic circuitry that regulates the voltage conversion on a switching power supply, Modern TV sets have switching powers supplies that converts the 120V AC to DC voltages that drives the circuits. You may have to replace the power supply.

I'm not clear on the four pins of the DC power supply for the speakers. Do you think there two different voltages needed??? It's not worth trying to convert your ac power supply/ It would take a few parts and you will not end up with 18 vdc. You can purchase a 18 v dc adapter for as little as 15.00.

( "Power Supply Problem Not Switching "???? )

How do you know it's Not Switching? Do you mean the TV wont turn on when you push the power button on and off on the TV and also with the remote control unit? Is that what you mean? If YES! Then, If your Vizio TV wont turn on and has NO-PICTURE, NO-SOUND and a BLACK SCREEN, Then the TV has an AC or a DC Voltage Problem.

1 - First, check the wall outlet socket by pluging in a lamp to see if you have 110 AC-volts there. If the lamp works, the wall outlet is OK! That means the problem is inside the TV.

2 - Before, you remove the back off the TV. I want to *(CAUTION - YOU)* The Power Voltages inside your TV are Very, DANGEROUS!!! There is 110 AC Volts at a 20-AMP-Rating ***CAN BE A LETHEL DEADLY SHOCK HAZARD to HUMANS!!!*** Also there are DC Voltages ranging from 3.3 to 24 volts. And R-F- VERY-HIGH-VOLTAGE of 20,000 Volts or More.

3 - You will need hand tools and a Digitle Volt Ohm Meter to check AC & DC Voltages and the OHMS Meter section to check resistors, capacitors, coils, grounds and contacts.

4 - With the Back removed, and no-power to the set. Inspect the power board for any signs of BURNED, LOOSE or BROCKEN parts like resistors, capacitors, coils, fuses on all boards. If you discover damaged parts, make a list of them. Then you must deside if you are qualified to do the on board repair or just order a new replacment board.

5 - If on the other hand you didn't discover any damaged parts by your inspection, It's time to put the Meter to good use. Plug the TV power cord to the wall outlet. Set the Meter for AC - voltage range of 200 or more. check for 110 AC volts going to the power supply board fused inputs.
If NO replace the cord. If YES, look on the board for voltage test points marked on the board. (SAMPLE!) 3.3 vdc, 5 vdc, 12 vdc, 24 vdc, and so on. Set Meter for DC Volts now, range 50 to 100. Put the black lead to ground and the RED lead to each test point marked on the board while repetetedly pressing the TV power on & off button..

6 - If ANY of the DC voltages were LOW, WRONG or MISSING, The Main power board is defective and needs to be removed and replaced with a new one. Write down the board number that is on the board and use that number to order the new one. You can order it on the Net!

*****(NOTE)***** If you are not an electronics tech. don't try to fix the old defective board... but, keep it handy, you might need it for parts later. :-)

Hope This helped... GOOD LUCK! NOW, GO FIX YOUR TV!

Pin Name Color Description
1 3.3V Orange +3.3 VDC
2 3.3V Orange +3.3 VDC
3 COM Black Ground
4 5V Red +5 VDC
5 COM Black Ground
6 5V Red +5 VDC
7 COM Black Ground
8 PWR_OK Gray Power Ok (is a status signal generated by the power supply to notify the computer that the DC operating voltages are within the ranges required for proper computer operation)
9 5VSB Purple +5 VDC Standby Voltage (max 10mA)
10 12V Yellow +12 VDC
11 3.3V Orange +3.3 VDC
12 -12V Blue -12 VDC
13 COM Black Ground
14 /PS_ON Green Power Supply On (active low). Short this pin to GND to switch power supply ON, disconnect from GND to switch OFF.
15 COM Black Ground
16 COM Black Ground
17 COM Black Ground
18 -5V White -5 VDC
19 5V Red +5 VDC
20 5V Red +5 VDC

/PSON activated by pressing and releasing the power button while the power supply is in standby mode. Activating /PSON connects the power supply's /PSON input to ground, thereby switching the power supply to full-on condition.
18 AWG is recommended for all wires except pin 11, which should be 22 AWG. For 300W configurations 16 AWG is recommended.
There are several ATX variants.
Hope this helps.
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you need to check the voltage output of your power supply section.This power supply supply is a switching type power supply.there is a chopper transformer in there.its supply is a dc voltage unlike any other transformer which is AC supplied on the primary..First step.
1.Using a multitester measure the primary supply it is a DC voltage around 220v - 110 VDC
2.Measure the secondary output.The out put is AC voltage the supply for the B+ going to plyback is 115vdc the second output is 12v run through a regulator and the regulator lower the voltage to 5vdc.this 5vdc supplies the system IC and the jungle IC.this ic process the switching of the plyback transformer and the plyback transformers output supplies the voltage of the whole system including your relay in the degaussing section....once the plyback is activated the tv will now turn on...

good luck!Hope i helped you..

please rate my help..god bless!

Power requirement is 12 VDC 1 amp.

>  checked voltages meter set to AC referenced to chassis VA, VE, etc no voltages. 
Do not try to measure voltages on the primary side of the power supply with a meter; you may damage the meter and cause new damage to the supply. There are switching frequencies somewhere between 50,000 - 100,000 Hz and possible voltage peaks of several hundred volts. 

Checking AC is only useful before a diode bridge that converts incoming AC into raw DC that is then chopped at higher frequency into an approximate HF AC, coupled to the secondary, then tapped and connected to more diodes to produce DC, finally regulated and sent on its way.
Your plasma set uses some higher voltages that could have caused the cracking sound they heard but the DVD player didn't cause the problem directly; maybe just caused the HV for the display to surge for a moment.
You may have additional fuses on the secondary side of the supply. If test points are accessible there, check for DC voltages and be suspicious of any fuse or test point that measures nothing at all.
I can't tell you which voltages to expect since that varies from one design to another but you should find several lower voltages such as 5 VDC for logic circuits and perhaps a 12 V point. The plasma's HV could be produced from a separate board fed from the AC line or get its supply voltage from the main supply. There aren't many standards to rely on here.      

The most likely semiconductor failure would be on the secondary side and diodes come in many different packages, many cylindrical, some in the TO-220 package with a metal flange and mounted on upright aluminum heatsinks. These will have only two leads and there will be some in the same package with three legs. The latter can also be checked statically but unless you know what kind of transistor or regulator (look about the same) you are measuring, you will not be able to ferret out a defective one with any luck. 
While you have the set open, check for any dust bunnies that can act as sponges, collect moisture and create a discharge path for higher voltages.