APS-254 power supply on a 40" sony

[dmesser100]

I have a bad diode on a aps-254 power board I cant identify, its the one with the red arrow pointing to at D6105. anybody know what I can replace this with?

[Agent24]

Re: APS-254 power supply on a 40" sony

I guess they are big rectifier diodes. If you find what they connect to, it should be evident what function they perform.

There seems to be a part number on them. I can make out a 4 on one and a 6 on the other. Desolder one and tell us what all the numbers are.

[budm]

Re: APS-254 power supply on a 40" sony

It looks like it is connected to the Aux winding of the transformer next to it to produce VCC voltage to the SMPS IC once the SMPS starts running.
Is the standby power supply section dead? Diode tested as shorted or open circuit?
http://www.shopjimmy.com/sony-1-474-...-g2-board.htm#

[anmol]

Re: APS-254 power supply on a 40" sony

Power Supply Sony AZ1-L G2LE_ APS-254 schem.

Regards

[dmesser100]

Re: APS-254 power supply on a 40" sony

Thanks guys, yes it tested shorted while the one beside it tested good. No standby power at all. Will desolder when i get home. There was another diode that tested ok but value seemed low, 217, while most test much higher. Can they be bad but short out?

[dmesser100]

Re: APS-254 power supply on a 40" sony

Ok its out but tests good out of circuit? what am I missing here. I tested the solder points and got 59ohms like when the diode was in

[dmesser100]

Re: APS-254 power supply on a 40" sony

the diode markings 4G, that's all that's on it

[tw2005]

Re: APS-254 power supply on a 40" sony

post #4 has a schematic, look at it, tells you what D6105 is and how it's all connected.

Assuming it's the correct schematic D6105 is 11EFS4 ,1A 400V FRED

[dmesser100]

Re: APS-254 power supply on a 40" sony

You are right tw2005, found a pic of it online with the numbers you provided. am looking over the schematic to get a better idea what to check next. thanks

[Agent24]

Re: APS-254 power supply on a 40" sony

It looks like D6105 supplies VCC to the PFC controller

Ok its out but tests good out of circuit? what am I missing here. I tested the solder points and got 59ohms like when the diode was in

You are measuring the components in parallel with the diode when you measure its pads, something else is giving you that reading of 59 ohms. It might be normal, or it might indicate something else is bad. Hard to tell, I think.

No standby power at all.

Have you checked that the supply is getting mains voltage OK, at least to the primary filter capacitor?

Is there anything else you have checked or tried?

[dmesser100]

Re: APS-254 power supply on a 40" sony

I put the diode back on the board and put power to it. im getting 65volts across the fuse. I thought it would read 120v ac. I have tested all diodes and transistors, seem ok.

[Agent24]

Re: APS-254 power supply on a 40" sony

A fuse is just a wire, close to zero ohms - if not blown, there should be zero volts across it.

If there is voltage across it, the fuse may be blown. Unplug the TV and check the resistance of the fuse, it should be approximately zero ohms\short circuit.

[budm]

Re: APS-254 power supply on a 40" sony

I put the diode back on the board and put power to it. im getting 65volts across the fuse. I thought it would read 120v ac. I have tested all diodes and transistors, seem ok.

Are you using chassis ground as the ground point for your meter?
What DC voltage do you get MEASURE AT THE TWO LEGS OF THE MAIN FILTER CAP 120uF 450VDC?
What resistance do you get between the Cathode pad of D6105 and the negative leg of the main filter cap?

[dmesser100]

Re: APS-254 power supply on a 40" sony

zero ohms on the fuse. I am using the chassis for a ground for the meter, I usually use an open screw hole on the frame. I have fixed the vizio ldr problems on my own TV's, and 6 others. So im still learning, try to research as much as I can before asking. but this one is a new ball game. and the 50" Samsung I just learned what was bad on it. will go thru the resisters tomorrow and anything else I can test.

[budm]

Re: APS-254 power supply on a 40" sony

When you work in the primary side of the circuit you do not use chassis as the ground ref point. When measure the DC voltage in the primary side, the negative leg of the main filter cap is the circuit ground ref point, when you want to check the Incoming AC voltage feeding the primary circuit, you measure between HOT and Neutral.
So what DC voltage do you have on the main filter cap?
What resistance do you get between the Cathode pad of D6105 and the negative leg of the main filter cap?

[dmesser100]

Re: APS-254 power supply on a 40" sony

OK now the only volts that are getting to the main board is a 3.3volt standby. but I hear now click or see any signs of life when I try to power up the tv

[dmesser100]

Re: APS-254 power supply on a 40" sony

I hear no clicking or signs I meant. Thanks budm, I will check those in the morning and get back

[budm]

Re: APS-254 power supply on a 40" sony

So did you put the Diode D6105 back in place OR you left it out?
If you leave out the D6105, then the standby power supply will be able to start up, but if you do have low resistance between the Cathode pad ans the primary GND, then if the diode is put back in it will stop the standby circuit due to heavy load on the cathode side of the D6105.
If you leave out D6105, then the PFC voltage booster circuit will not function so the TV will not start up properly, we need to know if you do have low resistance on the Cathode pad of the D6105 or not.

[dmesser100]

Re: APS-254 power supply on a 40" sony

I put it back in. It tested good out of circuit. If im getting standby power to the board, could it actually be the logic board that has the problem?

[budm]

Re: APS-254 power supply on a 40" sony

So that low resistance reading on the pad of the Diode is gone?
You need to find out next if you do have PS_ON signal from the main board or not to turn on the PFC Voltage booster which the DC Voltage on the main cap should go up from 170VDC (if you are in the USA) to about 400VDC when PS_ON is present.
BTW, we need the model number of this TV and the pictures of the whole back side of the TV so we can see what we are dealing with here.