Sharp LC-40LE810UN question

[tibimakai]

Re: Sharp LC-40LE810UN question

You are referring to the diodes after the traf?

[tom66]

Re: Sharp LC-40LE810UN question

Yes.

[budm]

Re: Sharp LC-40LE810UN question

So you get no DC on the 2200/16V cap C7961A, C7962A at all?

[tom66]

Re: Sharp LC-40LE810UN question

Very well reverse engineered, bud. Since OP is getting 5.5V, the charge resistor for the startup cap is likely okay, but it could be a shorted diode, shorted load, bad source resistor...

[budm]

Re: Sharp LC-40LE810UN question

This is what I come up based on your pictures, I cannot read all the part designators on the board.

[tibimakai]

Re: Sharp LC-40LE810UN question

Thank you Bud for all the work that you have done on Labor day, while I was at the beach. I really appreciate it.
I have measured all the requested voltages, here they are:
Tom, here is that IC's voltages(36BS3LJ):
Pin #1=0V
#2=4.94V
#3=0.7V
#4=0V
#5=109.5V
#6=0.003V
#7=6.62V
#8=0V
Bud, the PFC IC(1608B, couldn't find what it is) doesn't look good at all, there is no voltage what so ever at any pin.
C7961A/C7962A=29.2V(brown+black caps)
C7912=5.4V(startup cap)
Fusible resistor it's OK
Snubber resistor=165V
FET here=165.9V
Source resistor=0V

[tom66]

Re: Sharp LC-40LE810UN question

The PFC IC probably only gets voltages when the set leaves standby.

Since there are no outputs, it can never leave standby.

Are the diodes OK?

[budm]

Re: Sharp LC-40LE810UN question

I did not look at the spec of the 36BS3LJ yet, but what is that pin 5 with over 100V on it?

[tom66]

Re: Sharp LC-40LE810UN question

I did not look at the spec of the 36BS3LJ yet, but what is that pin 5 with over 100V on it?

That's possibly the high voltage startup cell built in to the IC.

[budm]

Re: Sharp LC-40LE810UN question

Never mind, I download the spec of the IC of SMPS for the standby IC, PIN5 is HV input from B+.
I need to trace out the details section of the Standby power supply section since we need to get it running first.

[tibimakai]

Re: Sharp LC-40LE810UN question

I haven't found anything shorted yet.
The components under the black heatsink seem like the two side ones are marked Q and the middle one is only D. One of the Q has four pins.
It's possible to be only one diode?

[budm]

Re: Sharp LC-40LE810UN question

Can I get more pictures?

[tibimakai]

Re: Sharp LC-40LE810UN question

Thank you again for all your hard work!!
I have made some quickly, hopefully they are OK:

[budm]

Re: Sharp LC-40LE810UN question

OK, I will look at them tomorrow. We need to get this section running first. What do you use for lighting since it is not day light right now?

[budm]

Re: Sharp LC-40LE810UN question

Can you show me the picture of your lighting setup for taking the pictures? I do not even see any shadows from the camera body or lens with MACRO shooting.

[tibimakai]

Re: Sharp LC-40LE810UN question

I have just used my magnifying lamp(two neon tubes on both sides of the lens) which was pointed from the left of the image. Why they are so good?

[budm]

Re: Sharp LC-40LE810UN question

Yes the picture is really good, it does not have he blue tint due to fluorescent lights.
By the way, I read how the SMPS for the standby voltage work, pin5 should rise up to about 18V due to the HV pin charges up C7912, then the IC will start running and the HV will be turn off and the VCC will be generated by D7913. So did you try replacing C7912 yet?
From page 7 of the IC spec:
The Undervoltage Lockout monitors the external
supply voltage VVCC. When the SMPS is plugged to the
main line, the internal Startup Cell is biased and starts
to charge the external capacitor CVCC which is
connected to the VCC pin. This VCC charge current is
controlled to 0.9mA by the Startup Cell. When the VVCC
exceeds the on-threshold VCCon=18V, the bias circuit
are switched on. Then the Startup Cell is switched off
by the Undervoltage Lockout and therefore no power
losses present due to the connection of the Startup Cell
to the Drain voltage. To avoid uncontrolled ringing at
switch-on a hysteresis start up voltage is implemented.
The switch-off of the controller can only take place after
Active Mode was entered and VVCC falls below 10.5V.
The maximum current consumption before the
controller is activated is about 250μA.
When VVCC falls below the off-threshold VCCoff=10.5V,
the bias circuit switched off and the soft start counter is

[tibimakai]

Re: Sharp LC-40LE810UN question

I haven't replaced anything yet, but I can look at it and see if I have one.

[budm]

Re: Sharp LC-40LE810UN question

OK, this is what I came up with, I cannot see pin1, 2 connections real well for the IC 7901.

[tibimakai]

Re: Sharp LC-40LE810UN question

Great work! I'm saying this because I know that I should be doing this.
When you have a todler you don't have time to do this kind of stuff.
I'm happy if I have time to measure a couple of parts or replace a couple of components.
So, we have this drawing and for what should I look for?


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