APS-254 power supply on a 40" sony

[dmesser100]

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

I will check that in the morning and get back

[dmesser100]

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

the resistance on the cathode pad with d6105 in circuit is 256 ohms, reversed it is 486. will be adding the pics here shortly

[budm]

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

And you were reading 56 Ohms when measured across the diode before?

[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.

So are you getting those voltages?

[rammar99]

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

After a recent thunderstorm, we're having a "dead" set issue that sounds like this thread. What was your final solution?

It is an APS-254 G2HE board out of a Sony KDL-40EX400 (2010) tv. Searching for that board, I first found the ShopJimmy kit that lists component locations and replacement parts for "common" issues with this board. I haven't been able to identify a bad component yet. The fuse is good, the resistors look close to the range printed, the diodes seem to be ok. Unable to test the small chips, I kept searching and found this thread.

When I check D6105 with it installed - it shows resistance in both directions like the dmesser first found. I haven't removed it, but when i check from the cathode of D6105 to the negative terminal on the main filter cap (C6325) I get about 550k ohms.

Thanks in advance for the help!
Ram

[rammar99]

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

I'm getting 3.3 volts on the secondary side, but no 12 or 24v at the connector pins if that helps.

Thank you,
Ram

[budm]

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

The 12V and the 24V will not be present until the board gets the command signals from the main board to turn them on, you need to find out if you have the command signals or not first.

[rammar99]

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

Budm - thank you for the response. I took the board out of the TV and have it on the counter to test more easily. Sounds like I need to put it back in tonight and try and turn it on again?

Before taking the board out, the system would not turn on with the remote or main power button.

What's the best way to tell if it is generating command signals?

[Agent24]

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

You need to measure the voltage of the PS_ON line with everything connected together. This voltage should go high when you press the power button.

According to the schematic already posted, this is line "Power On" - Connector CN6401, Pin 3.

[rammar99]

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

Sorry for the delayed response, I got called out of town this past week. Just got to perform the "Power ON" test with the board back in the TV and there was no change in voltage. 3.3v side stayed at 3.3v when hitting the power button and the 12v side remained dead at 0v.

Thoughts or next suggestions on what to test next?

Thanks in advance.

[rammar99]

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

Just to clarify, I did test CN6401, Pin 3 (Pwr On) and didn't get even a momentary change. Also tested between 12v (Pin 8,9) and ground (Pin 6,7) with nothing there either when the pwr button was pushed.

[rammar99]

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

Does that confirm it's the APS-254 board (power supply) and I should try to have it repaired or find one on ebay? I haven't found a failed component yet probing around - but then I'm a chemical not electrical engineer.

Thanks

[budm]

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

So the PWR-ON pin 3 stays at <1VDC then? if that is the case, it is the main board that is not sending the ON command to turn on the power supply.
Typical PWR-ON command signal:
<1VDC = power supply OFF, >2.5VDC = Power supply on

[rammar99]

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

budm - that is correct. I just re-verified and i get 3.3v on pin 1 but 0v on pin3 even when pressing or holding the power switch. I was reading back through the sticky on basic troubleshooting and it was talking about 5v as a common "standby" power. I don't see any 5v power on the diagram or on the board. The set is completely dead, no standby light on the front panel - so I was actually surprised to find the 3.3v working. Does Sony use the 12v power for "standby" or should I be looking for 5v somewhere as well?

That may just be a curiosity, because at this point I think we've proved it's an issue in the power supply board for sure. I just haven't been able to trace it to a specific location - fuse, resistor, diode, etc. Any other thoughts to check or test before trying to buy a replacement?

Thanks again

[budm]

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

Not all TVs use 5VC for standby Voltage, in this board it uses 3.3V for standby Voltage.
You might as well those yellow small fusees such as PS6401, 6402,etc.

[rammar99]

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

Both of those locations have good conductivity across them. I didn't see any other similar yellow components but I did look at FB6101 and FB6102, down by the incoming power that looked like they might be fuses. Unfortunately both had conductivity across them as well, so still no smoking gun.

[budm]

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

I have you checking those fuses just in case, they are not related it to not having no PS-ON from the main board.
BTW, do you do see any error LED blinking codes?
You may try disconnecting the cables between the main board and the T-CON board to see what will happen next, something may have locked out the PS-ON also.

[rammar99]

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

No LED's active at all, nothing has lit up or flashed since the storm. That's why i was thinking it was a fuse. But seeing the 3.3v and continuity on the fuses seems to prove otherwise.

Just pulled the cables one at a time and no change. nothing on pin3 and ground. Not sure if it's helpful, but I am getting 0.16v on pin 2 which is labelled "AC OFF DET". Looks like that runs through a diode and back from pin 23 on IC6301. That IC is in the "common" repair kit, but not sure i can test it with a simple voltmeter. Does that voltage look normal or suspect?

Thanks

[budm]

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

I do not remember if the AC OFF DET is supposed to be high = normal or LOW = normal.

[budm]

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

You may want to read these threads:
https://www.badcaps.net/forum/search...archid=5022586