LF501EM5F No Power, Chirping/Beeping Transformer

[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.

[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

[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.

[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?

[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

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

We need to trace out the input pin to see where it goes to, it should go the the AMP+13V pin. Also check the resistance between input pin and GND to see what you have.

[budm]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

BTW, if you check the resistance between the big tab of that 1117 and the ALL+3.3V jumper on the power supply board, does it show <1 Ohm?

[budm]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

BTW, the prints on the 1117 IC, does it show as 1117-33?

[shadetreetrader11]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

.3 OHMS and that's doing the math for the loss in the test leeds. And yes sir the 1117 I found was 3.3vdc

[shadetreetrader11]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

wow output center large tab to ground is .5 ohms OUCH!! ok I'll try trace that back tonight. I have a schematic for the main board I'll check back later on in the evening

[budm]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

.3 OHMS and that's doing the math for the loss in the test leeds. And yes sir the 1117 I found was 3.3vdc

So the one on your main board does have 1117-33 printed on it then? Just want to be sure.
So it does look like the 3.3V is generated on the main board and then sent back to the power supply board, that is why so many parts are left off the power supply board.

[budm]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

wow output center large tab to ground is .5 ohms OUCH!! ok I'll try trace that back tonight. I have a schematic for the main board I'll check back later on in the evening

Did you upload the diagram of the main board?

[budm]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

wow output center large tab to ground is .5 ohms OUCH!! ok I'll try trace that back tonight. I have a schematic for the main board I'll check back later on in the evening

That reading is with or without the cable between the main and power supply board connected?
There is a small ceramic cap C3608 connected between the tab and GND, those kind of cap tends to fail as shorted circuit.

[shadetreetrader11]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

It didn't say 33 on the IC. But page 54 of the service manual has it labled as 3.3 volts. (Top Center of schematic)
And center pin of IC to ground was with the ribbon cable disconnected

[budm]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

If pin 1 of that 1117 IC has two resistors connected to it then it is not a fixed Voltage regulator but an adjustable regulator. The fixed output regulator pin 1 will be connected to GNDa and the body will be printed with something like 1117-33 for 3.3V fixed output, the adjustable type will only has 1117 printed on it.
I will look at the manual.

[budm]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

That manual is for EM4, you have EM5F that is why the power supply board diagram show the 1117-3.3V but the actual board does not have it installed.
The diagram shows it gets the Vin from P-ON+5V power supply generated by IC3003 buck regulator which it gets the Voltage from P-ON+21V.
Looks like we need to find the correct diagram that matched your TV model/version.

[shadetreetrader11]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

I should prob put the original IC back on?

[budm]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

At this point, yes.

[shadetreetrader11]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

I looked for correct schematic with no luck.