LF501EM5F No Power, Chirping/Beeping Transformer

[budm]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

No luck on the correct diagrams for either the power supply or the main board, but at this point you know that you have low resistance between the output pin (big tap of the 1117) and GND so maybe you will have to trace that out, and a far as the input goes, you just need to trace it out as to where it goes to.

[shadetreetrader11]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

Any luck with schematics. I was thinking It would be cool to fix this thing. I have seen this is a fairly common thing with these tvs. Everybody just buys a knew main board for it and calls it quits. But If we go threw the work and fix it it might help some others. Either way it's up to you. Like I said I can't find the correct schematics.

[shadetreetrader11]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

Well maybe that's my problem. I'm using less expensive solder. I guess I'm a tight Dutchman. I'll have to look that up and try it out. Would probably take care of some issues

[stj]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

i use Stannol TC with Kristall505 flux.

when it runs out, i may switch to TC with HS10 or KS115 flux
it's not as clean as Kristall505, but more agressive on dirty joints.

[shadetreetrader11]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

Well I guess the picture makes it look that way, Because I know what you are saying and I think the the light must be messing with a guys eyes. Just out of curiosity what kind of solder do you use?

[stj]

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.

that joint has a micro-fracture.

it's not the magnifier, it's knowing what your looking at.
the shadow changes half way up the joint - it has a ring-crack.

[shadetreetrader11]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

I looked for correct schematic with no luck.

[budm]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

At this point, yes.

[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

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.

[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.

[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

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.

[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

.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.

[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

[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

[budm]

Re: LF501EM5F No Power, Chirping/Beeping Transformer

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

[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

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.