Re: Sharp LC 60LE655U 2 long flashes + 2 short flashes
Does anyone know anything about an IC labelled S101 241A ?
It is part of the AC-DET circuit on the hot side of the board.
I could not find any info on it at all.
Attaching a picture of the label in case I'm reading it wrong....
carsearch07
Member
Last Activity: 08-08-2018, 02:00 PM
Joined: 05-31-2018
Location: Olathe
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Re: Sharp LC 60LE655U 2 long flashes + 2 short flashes
R_J, sorry for the delay. I've been looking at this closely.
Here's my theory on what is happening:-
1. When PS_ON is supplied, UR is rising to above 14.4 V momentarily which is above the 13.2 V expected for UR.
2. Due to this voltage, the gate voltage on SCR Q7305 is high enough to turn the SCR on and it latches ON. This diverts current away from the opto PC7904 and acts as protection circuit.
So the crux of the problem is that UR is getting a higher voltage than expected. This points...Leave a comment:
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Re: Sharp LC 60LE655U 2 long flashes + 2 short flashes
Thanks attainteddragon and R_J.
The diode tested fine after I lifted one leg. It was indeed a IN4148.
I still think the problem is in that general area of the board. The opto PC7904 has 0.6V on its diode side which means a very small current is flowing through it.
If the opto diode current increases,
--> the transistor side of the opto would see a drop in resistance,
--> the Q7902 transistor would turn on
--> Vcc would reach IC7601
and thus the UR13.2...Leave a comment:
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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....Leave a comment:
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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?Leave a comment:
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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...Leave a comment:
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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.Leave a comment:
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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....Leave a comment:
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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...Leave a comment:
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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!Leave a comment:
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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....Leave a comment:
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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?Last edited by carsearch07; 06-09-2018, 05:26 PM.Leave a comment:
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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.Leave a comment:
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Re: Sharp LC 60LE655U 2 long flashes + 2 short flashes
Thanks R_J.
Anything further I can check?
I noticed that the gate of Q7801 is more than 600 VDC! My meter only goes to 600 V DC and it's shows OL in that range between the gate and hot ground. I'm surprised at such a high voltage especially since the largest capacitors on the board are at 400V and also in parallel with each otherLeave a comment:
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Re: Sharp LC 60LE655U 2 long flashes + 2 short flashes
Off-topic curiosity:
I spotted a couple of things on the board ( Picture attached)
1. Why does the trace split into 2 sections with a thin empty line between the 2 sections? Any advantage over one solid trace?
2. There is a chevron-shaped hole under each FET between the pins and the heat sink boundary. What's the purpose of these holes?...Leave a comment:
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Re: Sharp LC 60LE655U 2 long flashes + 2 short flashes
Yes, confirmed. 167 V goes to 412 V
I'm not sure which terminals of the FETs are gate,drain or source. Is the middle one always the gate? I can't see the FET label unless I desolder the heat sink first.
Q7601
Middle terminal = 412 V
Both other terminals = 0 V
Q7602
All terminals = 0 V
The voltage on PC7902
pin 3 to ground = 4.52 V DC
pin 4 to ground = 4.95 V DC
pin 4 to pin 3 = 0.31 V (I would have expected this...Last edited by carsearch07; 06-08-2018, 04:17 PM.Leave a comment:
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Re: Sharp LC 60LE655U 2 long flashes + 2 short flashes
Voltage across PC7904 is 1.02 VDC on the secondary side and 0.8 V DC on the primary.
With the power supply off, Q7902 has
Base = 15.9 V DC with respect to BD (-)
Emitter and Collector = 0 V
With PS_ON,
Base reduces to 15.5 V
Collector = 14.9 V
Emitter = 14.2 V
(I may have mixed up the terminals for C and E)
I have double checked that there is no voltage across C7204,C7205 and C7130.
Is there a way to see if the big...Leave a comment:
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Re: Sharp LC 60LE655U 2 long flashes + 2 short flashes
R_J,
I noticed that a small part of your yellow line trace is incorrect. You have it going up obliquely to the left but I was able to confirm that it goes downward (with a light behind the board) Picture attached....Leave a comment:
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Re: Sharp LC 60LE655U 2 long flashes + 2 short flashes
Off-topic curiosity :
I noticed that the PCB has some red sections on top of some traces as well as under some Surface mounted devices. Is that some kind of insulation?...Leave a comment:
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Re: Sharp LC 60LE655U 2 long flashes + 2 short flashes
Thanks R_J. Truly appreciate your input and the efforts you took to draw the circuit for me.
D7901
Forward Bias resistance(FB) = 688 ohm (on 2K scale)
Reverse Bias resistance (RB) = 1465 ohm (on 2K scale)
Voltage across with PS_ON supplied = 0.6 V
Do these readings look ok?
For reference, I also took readings for 2 other zener diodes
D7913
FB = 783 ohm ; RB = 29.6k ohm ; V = 1.4 V (in both states of PS_ON)
D7907
FB = 800 ohm...Leave a comment:
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