Sharp LC 60LE655U 2 long flashes + 2 short flashes

[R_J]

Re: Sharp LC 60LE655U 2 long flashes + 2 short flashes

I don't think your measuring the gate, likely the drain and it could be that your meter is picking up the high frequency pulse from the circuit.
That is the pfc circuit, and it IS working.
I can't remember but did you ever check the voltage on PC7601 opto, pins 3 & 4 are on hot side, 1 & 2 on the cold side, check in standby, then check them with power on. Its about the only thing left that could be shuting down the circuit

On the cold side of PC7601 is the 13.2v-ovp circuit, which could shut down that part of the power supply.
I guess you could check all those diodes, including D7131, in the seconday of that T7601 transformer, just make sure none are shorted, D7131 might show low, .2-.3 in diode test as there are 2 diodes in parallel and are likely shotkey type

[carsearch07]

Re: Sharp LC 60LE655U 2 long flashes + 2 short flashes

PC7601 doesn't seem to be doing anything. Both input terminals (1 & 2) are 0 V in standby and in powered states. Since it is a protection circuit, it's probably normal, right?

I checked all diodes; none showed up as shorted.

[carsearch07]

Re: Sharp LC 60LE655U 2 long flashes + 2 short flashes

I'm trying to get access to an oscilloscope to continue testing. Any pointers on how to make my way around the board while testing with an oscilloscope?

Also, I haven't been providing the PNL-POW signal just the PS_ON signal. Should I try providing PNL-POW using a 1k resistor from BU5V? What should change once it's applied?

[R_J]

Re: Sharp LC 60LE655U 2 long flashes + 2 short flashes

If you are using a scope on the hot side you need an isolation transformer, or else when you connect the ground in the hot side you will blow the power supply. on PC7601 3 & 4 pins?
If you look at the pdf for the ssc9522s you will see the opto (led) gets lit when there is voltage on the secondary and the opto (photo diode) controls the fb pin on the ic
When the VCC pin gets its 14 volts that ic should turn on and give at least a cycle or two to produce at least some voltage on the secondary so the supply can keep running.
I'm almost starting to think the ic could be bad.
Another possible could be an open C7603, If this was a samsung and that cap was white and square (and bulged)... but these types are usually ok, if you are able to check it it might be worth a try

[R_J]

Re: Sharp LC 60LE655U 2 long flashes + 2 short flashes

Another thing to check is on IC7601, what is the voltage on pin 1?, Vsense. You should have about 1.4 volts (to hot ground), if you do not, check J7035 (0Ω) and those high value resistors, R7605,R7606, R7621, and maybe check the R7801,7802,7803 also
I know on some tv's these high resistance resistors can go open, there usually are 3-4, 1+ meg Ω in series
Here is a circuit from a Toshiba power supply that uses the same ic

[carsearch07]

Re: Sharp LC 60LE655U 2 long flashes + 2 short flashes

Thanks R_J.

On PC7601 3 & 4 pins stay at 0 V all the time.

On IC7601, the voltage on pin 1 Vsense = 1.7 V

R7605,R7606, R7621, = 1.2 M ohm....moves up and down a bit. ( The label says 1504 so shouldn't this be 1.5M ohm ? )

R7801,R7802,R7803 = 2 M ohm moves a bit
J7035 = 0 ohm

How do I test C7603 without lifting one pin? My soldering skills are poor so that will be my last resort after I reach the limits of testing with my meter and an oscilloscope.
The meter reads 0 V across C7603 all the time.
When the circuit is off, in continuity mode on the meter, C7603 gives 458 in one direction and OL the other way

[R_J]

Re: Sharp LC 60LE655U 2 long flashes + 2 short flashes

C7603 would need to be checked wiyth a cap checker, It is very likely ok. the resistors seem to check ok, Like I said sometimes they go open. 1.2M is close enough to 1.5M
You say you have a scope, If you monitor any of the secondaries on T7601, do you see any change at all when you press the power button? even one pulse?
And maybe check the resistance between 14 & 16 of T7601, I doubt is open but I'm running out of ideas.

Is that a portable scope by chance or does it need to be pluged into a/c If it does'nt need to connected to the a/c line it could be used to check the primary circuits.
There is always a chance the ic is bad

[carsearch07]

Re: Sharp LC 60LE655U 2 long flashes + 2 short flashes

I don't have a scope yet but I'm hoping to have access to one and an isolation transformer soon. I'll keep this thread updated with my findings.

Thanks a lot for all the help so far. I appreciate it very much!

[carsearch07]

Re: Sharp LC 60LE655U 2 long flashes + 2 short flashes

Hi,
I replaced the IC7601 (ssc9522s) on the board but it hasn't fixed the issue.

With the board connected to other boards on the TV, the behavior has changed. There is no sign of life...no flashes or anything. Only thing is that I could hear a short soft click every 11 seconds from the main transformer. It appears that the main board is sending the PS_ON signal repeatedly now.

With the board on the bench, when PS_ON is supplied, the UR13.2 pin has a momentary voltage ~10V and rapidly falls to 0 V.
The voltages on the pins of ssc9522s IC7601 have also changed after replacing the IC
Vsense (pin 1) = momentarily 0.5V and then falls to 0 V
Vcc (pin 2) = momentarily 5 V and then falls to 0 V

I tried to trace the voltages feeding into Vsense. It seems that my meter (in DC voltage range) is affecting the circuit because when I lift the probe from R7606 1.5Mohm resistor the voltage drops from 137 V to 0 V (after touching probe back to the same point!)

Any thoughts on what I should check next?

[R_J]

Re: Sharp LC 60LE655U 2 long flashes + 2 short flashes

I don't know, when you turn the board on what does the voltage on the large cap C7800a/b do? it should be 160 volts in standby then rise to 400v when the pfc starts. Just to be clear you are using the hot ground on the primary side to check voltages right?

Is that picture of the ic before or after you changed it?
Check the voltage on PC7601, secondary side, you were getting 0 before, is there voltage there now?
Am I correct that you had no ur13 before and now it comes up albeit low.

It seems like that power supply section is trying to work but is shuting down. Before you did not get any secondary voltages off that transformer right? what do you get across C7200a or b now?

[carsearch07]

Re: Sharp LC 60LE655U 2 long flashes + 2 short flashes

C7800a/b give 170V initially. With PS_ON, the voltage momentarily goes to around 320V but then comes back to 170V. (Before I replaced the IC, I would get 450V )
Yes, I am using hot ground.

The picture is after I changed the IC.

The secondary of PC7601 momentarily gives 0.1 V with PS_ON supplied and then goes back to 0 V. Honestly, I never checked it for momentary voltages before. I always found it at 0 V before.

I am also not sure if UR13 used to provide any momentary voltage before. My guess is that it didn't because I never heard the click of the transformer before and it always showed 0 V. Currently it gives a lower voltage but just for a fraction of a second.

I'm not able to find C7200a/b....did you mean something else? Do you mind pointing it out for me?

I also found that the voltage across the PRIMARY of the big transformer momentarily shows as 450 V (meter in DC mode or AC mode) and then goes back to 0 V.

I agree that it does seem like the power supply is shutting itself down.

Thanks for the response, R_J. I really appreciate you taking the time to read about my problems and helping me through this.

[R_J]

Re: Sharp LC 60LE655U 2 long flashes + 2 short flashes

I would check all the diodes off the transformer secondary, also check across the filter caps to make sure there are no shorts on any of the supplies.
I looked at the wrong board, The caps are C7130 or C7225. I just wanted to see if there was any voltage in the secondary

You said earlier you checked the diodes in the secondary, there are a lot of them, some dual diodes like D7131 and all the diodes for the led backlights, it only takes one to be shorted.


Note for me RUNTKB109WJQZ (DPS-167CP A)

[carsearch07]

Re: Sharp LC 60LE655U 2 long flashes + 2 short flashes

C7130 momentarily shows 13 V and then falls to 0 V
C7225 is not installed

I didn't find any shorts on the secondary diodes.

[R_J]

Re: Sharp LC 60LE655U 2 long flashes + 2 short flashes

Are you still bench testing this or did you try it in the tv? The reason I ask is it is possible that the 13v being unloaded could be going into over voltage protection.
Do the led 1,2 & 3 votages come up, they should be around 170v I believe

[carsearch07]

Re: Sharp LC 60LE655U 2 long flashes + 2 short flashes

I tried with the TV again and have the same behavior i.e. PS_ON is sent every 11 seconds by the mainboard but the power supply doesn't stay on.

The momentary voltages on the LED cable are as follows:-
LED 1+,2+,3+,4+ = ~120 V
LED 1-,2-,3-,4- = ~44 V
(All voltages with reference to chassis ground)

To take the idea of a protection circuit a bit further, it seems like the Vsense and Vcc (on the oscillator IC ) fall to 0 V which effectively disables the IC. So if I trace backwards, the voltages seem to come from the area near the 3 opto couplers at the bottom.
The lowest one PC7902 feeds from PRIMARY to SECONDARY.
The other 2 optos PC7903 and PC7904 feed from the secondary to the Primary. I suspect one of these two will lead me to the problem. What's the correct way to test them?

[R_J]

Re: Sharp LC 60LE655U 2 long flashes + 2 short flashes

by ocsillator ic? do you mean IC7601 or a different one? there is also PC7601 that also controls IC7601
I believe PC7903 is feedback for the standby ic7903, PC7904 I believe is the power on opto

There should be standby VCC on C7918(+) What is the voltage and is it steady?
That voltage should be on Q7902 collector, Q7902 emitter supplies VCC to the IC7601 and IC7801 (pfc) to turn them on.
The base of Q7902 is controlled by optocoupler 7904

[carsearch07]

Re: Sharp LC 60LE655U 2 long flashes + 2 short flashes

Yes, I meant IC7601.

C7918(+) = 17.1 V steady = collector of Q7902
Emitter and base of Q7902 = 0 V = PC7904 receiver side (-)
I guess the fault is that the Base voltage is not being provided.

Voltage across transmitter side of PC7904 = 0.6 V
The voltage across receiver side moves around a bit before settling at 6.57 V.
Is this to be expected?

[carsearch07]

Re: Sharp LC 60LE655U 2 long flashes + 2 short flashes

I have some suspicions on D7310 on the secondary side.
Resistance on 2K scale of my meter:-
Forward bias = 0.68 K ohm
Reverse bias = 1.95 K ohm

Does this indicate a problem? I would think the RB resistance would be much higher.

I can't tell which diode it is. The label seems to say PH. Attached picture.

[attainteddragon]

Re: Sharp LC 60LE655U 2 long flashes + 2 short flashes

that zener diode is most likely fine. lift one leg and test both ways in diode mode. as long as it is not shorted or open, then your all good.

[R_J]

Re: Sharp LC 60LE655U 2 long flashes + 2 short flashes

Thats likley just a 1n4148 diode, not a zener. When you try and measure it the way you are you are measuring all the other components connected to it, If you suspect it, lift one end and use diode test.
There are likely other numbers on it