LF501EM5F No Power, Chirping/Beeping Transformer

[shadetreetrader11]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

OK So the center larger tab is reading 24mv and with the tab on the top from left to right it reads 24mv 24mv .812 vdc So I then decided I would quickly change out the 1117 be cause I have some laying around and nothing changed. Seems as though we are missing our 8 volts. I also took the resistor out of line to force it on. I have a bk precidion 1715 power supply. Is there any way I can forget about using the main power supply and hook that up instead for a little while. I cant trace anything down because it just cycles over and over again. All the readings I have given you have been in the min max mode so WHO KNOWS

[budm]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

Check and report the DCV readings of all 3 pins, note: the big tab is connected internally to the center pin.
If you look at it with the big tab on top, the left pin is GND/ADJ pin, the middle pin/Tab is the output pin, the right pin is the input pin which should show around 8V, the middle pin should show 3.3V. It may be as simple as bad 1117 which is a common failure in Vizio TV and some other TVs as well.
So have all the board connected then apply the power but do not turn on the TV, we need to check for 3.3V in standby/off mode.
I think we are getting close.

[shadetreetrader11]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

BudM. Yes sir you are correct, part number IS 1117 for IC 3602. Same part number that our schmatics had for the power supply. So now the question is how do we see if that sucker is working?

[shadetreetrader11]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

Dick I looked at D655 over and over again. I put them under a Enhanced Vision Magnifer. And to be honest with you I think you should do the same.

[dick_barton]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

Some of the solder joints of the diodes that have been lifted do not look so good especially D655

https://www.badcaps.net/forum/attach...6&d=1463463062

[budm]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

BTW, here is main board and the 3.3V regulator IC3602.
It will good if you can at least verify the DCV on that IC so that we can understand how this version of this TV is setup.
Pictures provided by shopjimmy.

[budm]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

No, not yet!
Is this your main board?
It looks like the ALL+3.3V is generated on the main board!
http://www.shopjimmy.com/emerson-a3a...ain-board.htm#

If it is, look at the P/N of IC3602.

[shadetreetrader11]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

Should we chalk this one up as a loss and I order one? It's up to you I'm game. But for now I'm going to bed. Have to be up at 6.30

[shadetreetrader11]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

[budm]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

OK the diagram does not match the board BA3AU0F0102 3.

Emerson A3AUNMPW-001 Power Supply Board.
http://www.shopjimmy.com/emerson-a3a...upply-unit.htm

[budm]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

Schematic on my post #45 is the one I use.
So now we have to trace out the connection from the 3.3V pin to see where it goes to, this is not going to be easy.

[shadetreetrader11]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

[shadetreetrader11]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

My board didn't come from the factory with IC651. The Board I have is ba3au0f0102 3. Now having said that I down loaded a print off the Internet and It also has IC651 in it.

[budm]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

Spec sheet of the FA5640:
Page 12:
Start up minimum Voltage is 12.5V, 14V Typ.
Under Voltage shutdown can be as low as 7V, 8V typ,
Right now you are getting Voltages at outputs (AMP13V and P-ON 21V) side so the IC is running otherwise you will have 0V at the output side of the transformer rectifier circuits.
You can verify that the IC does start up and run or not by lifting one of the 3 resistors R610, R611, or R614 which feed pin 8 (VH) for the internal charge pump circuit and see if you will have any DCV at the output side of the transformer at all.

After looking and studying how the circuit function, I suspect the problem is at IC651 (1117 series 3.3V fixed LDO regulator) or open circuit or high resistance at the input pin due to bad resistors connected to the input pin, it should have about 8VDC feeding the input pin right now (that is what you reported for the AMP13V), that is more than enough to get the IC651 to put out 3.3VDC at low current to run the main board in standby mode.
Once the PS-ON is present then Q653 is turn on so the feedback resistor R667 is grounded out so the output Voltages will go higher to maintain the higher output Voltages and keep the sensing pin of D650 (431 shunt regulator Diode) at 2.4V) which causes the rest of the Voltages to go up to the proper level. They had to keep the out put Voltages at low level in standby mode so the power consumption will be low, that is why the 13V and the 21V are low right now since it is not required full Voltage in standby mode, it will kick up to proper Voltage and then the 3.3V will be handle by Q657 which can handle more current than the 1117can supply when TV is in full on mode and requires more current from the 3.3V power supply, at the same time the PFC Voltage booster will be running also.

So the bottom line, in standby mode:
The AMP+13V will be around 8V. This 8v is high enough to feed the 1117 3.3V LDO regulator IC to provide 3.3V at low current to run the main board in standby mode.
The P-ON-+21V will be around 13V
You can also see that the 13V and the 21V is putting out at 60% of the normal Voltage and being maintained at that level in standby mode.
The ALL+3.3V SHOULD BE AT 3.3V!
So you need to check the Voltage at IC651 1117 3.3V

[shadetreetrader11]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

I'll spend some time just poking around with the ohm meter maybe I'll get lucky ha ha

[CapLeaker]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

no. If there would be something wrong with those, you would know it. For some reason the circuit does not start. We proved that already by not having enough voltage on the IC. Let it be a starting cap, a starter resistor etc. Did you check those capacitors in post 58?

[shadetreetrader11]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

I just thought of something. Should I take the transistors or mosfets or what ever they are out of circut to check them? Q17014 Q1601 Q1602 Q601 They are attached to the alum. heat sinks I know for a fact none of them are shorted. But as far as working properly I can't really say

[shadetreetrader11]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

All+3.3 to ground is 56.3k
All+3.3 to ground with the 470 ohm resister to p on is 3.4k

[budm]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

Right now the circuit is working otherwise you will not have any of the outputs Voltages at all, it is just not putting out the correct Voltages, and we are not going to have any boosted Voltage because it is getting the VCC to run the PFC IC from the AUX winding of the main transformer which I am pretty sure that it is also low, it also need the PS-ON for the PFC to come on line.
What resistance do you have between GND and the ALL+3.3V line?

[CapLeaker]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

I figured so... go measure a ceramic cap with a ESR meter at different frequencies and see what you get. There is no point of measuring ESR on a ceramic cap on this power supply.