What I was getting at is that it might be possible to make a dummy plug to trick the TV to thinking there's an input. Or just repurpose an old Chromecast or Android TV box. Actually you could probably just plug in a USB with a JPEG and put the TV on slideshow mode.
But if you did want to hack the hardware, it would make more sense to find the power on signal on the motherboard and tie that to high if you are keeping the mobo in place. Otherwise remove the mobo and drive DRV_ON and PDIM directly.
maneatingmonkey
Member
Last Activity: 11-19-2024, 02:29 AM
Joined: 02-28-2020
Location: Sydney, NSW
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Yes a lack of PDIM signal could absolutely be causing the flicker.
But TBH I'm not sure why you want to bypass the signals from the mainboard if you want to use it anyway for audio. Unless a sleep timer has been specifically set, the screen shouldn't turn off so long at there is a video input connected.
So hook up a laptop to HDMI1 and load up a 10 hour YouTube video, making sure the PC audio is set to TV speakers. You can the change the input on the remote either by pressing SOURCE, DOWN, ENTER repeatedly (if the selection starts from the current source), or doing the...Leave a comment:
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DW about measuring the current. For a 3V digital signal the midpoint is 1.5V, so theoretically any voltage above that should be treated as ON an anything below that should be treated as OFF. It's a little more complicated than that in practice, so I wouldn't rely on using on one battery.
As for why the LEDs are flickering, I'm not sure. Does the service manual say anything about the MS pin? What voltage does it read when connected to the mainboard?Leave a comment:
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[FONT=Arial][SIZE=14px]Update: VGL came back after cutting CK1. I then cut LC1 and LC2, but still no VGH. I proceeded to cut all the other clock lines one by one, then finally after cutting ST I finally got VGH and a picture.
Immediately I noticed two things. 1) A vertical line down the entire screen, but this is on the secondary panel board side of the TV so probably unrelated. 2) A rounded corner near the shorted CK and LC lines. Zooming in reveals a tiny bubble in the bezel of the panel. I suspect the short lies beneath this point and melted the plastic.
Either way,...Leave a comment:
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Hey, so backlights on a TV are controlled by a PWM signal, whereby 50% duty cycle corresponds to 50% brightness, etc. You can't accurately measure this signal with a multimeter. A reading of 2.2V would correspond to a 3V signal at 75% duty cycle though. (Mathematically, it could also be a 220V signal at 1% duty cycle, but since PWR_ON is supposed to be 3V, we can assume a common signal voltage level).
So if you wanted to run your TV at max brightness, in theory all you need to do is supply a constant 3V DC to PDIM. I'm not sure why this isn't working for you. Can you measure the voltage...Leave a comment:
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[SIZE=14px][FONT=Arial]Thanks Iotas!
Resistances to ground:[/FONT][/SIZE] [TABLE="class: MsoTableGrid"]
[TR]
[TD][SIZE=14px][FONT=Arial]ST[/FONT][/SIZE][/TD]
[TD][SIZE=14px][FONT=Arial]>20kΩ[/FONT][/SIZE][/TD]
[/TR]
[TR]
[TD][SIZE=14px][FONT=Arial]LC1[/FONT][/SIZE][/TD]
[TD][SIZE=14px][FONT=Arial]0.26kΩ[/FONT][/SIZE][/TD]
[/TR]
[TR]
[TD][SIZE=14px][FONT=Arial]LC2[/FONT][/SIZE][/TD]
[TD][SIZE=14px][FONT=Arial]0.25kΩ[/FONT][/SIZE][/TD]
[/TR]
...Leave a comment:
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Have you inspected the pins inside the port? By far the most likely point of failure.Leave a comment:
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How are you driving the PWR_ON signal? That should also be around 3.3V, no?Leave a comment:
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Missing LCD Panel Voltages VGH, VGL, VCOM (TCL 55P6US Sound & Backlight but NO Picture)
[SIZE=14px][FONT=Arial]I have a TCL 55P6US with sound and backlight but no picture. This model does not have a T-CON board, and the right (rear perspective) panel board is fed from the left panel board. I have not been able to induce any change by disconnecting the secondary panel board or the tape cut-off method on the primary board.
There are a bunch of voltages missing on the panel boards. I can't find any shorted caps of the panel boards, and all of the missing voltage rails read in the kiloohms, which leads me to suspect the issue may lie on the circuit board, rather than a short... -
If you want to be "scientific" you could compare resistance values for each clock and data line between the left and right panel boards. But the quickest way is to just binary search - i.e. tape off half the pins, then a quarter, then an eighth, etc....Leave a comment:
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[FONT=Aptos]Thank you [USER="112742"]triplefour[/USER] and others for your posts. I had the same TV with the exact same symptoms as the OP. Thanks to this thread, I was able to isolate the problem down to a shorted clock line #8 in the left side of the panel. Unfortunately without this signal the image is unwatchable, but at least I was able to confirm the integrity of the other components.[/FONT]
triplefourLeave a comment:
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Re: Thinkpad Edge E540 missing PM_SLP_S5# and VM_PWRON
If I tie VM_PWRON to 3V then the downstream devices (SPI chips, +1.05VMP rail) get power as expected, but that's it. However, if I instead tie PM_SLP_S5# to 3V, then the laptop actually POSTs when I press the power button.
PM_SLP_S5# is sent from the PCH to the EC.
Question 1: How can I isolate if the problem is with the PCH or further upstream? What input signals does the PCH need to assert PM_SLP_S5#?
Question 2: How bad of a workaround is it to leave PM_SLP_S5# connected to 3V...Leave a comment:
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Re: Thinkpad Edge E540 missing PM_SLP_S5# and VM_PWRON
Resistance: 91kΩ (black on ground)
Diode mode: 700 on the dot (red on ground).Last edited by maneatingmonkey; 01-28-2023, 08:01 AM.Leave a comment:
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ThinkPad E540 NM-A161 _ Rev:1.0
[COLOR="Red"][Mod. Edit-Vesko356] [/COLOR]Files copied from a thread in the Tech Forum
[B]To help other forum members looking for this schematic[/B], not just the OP - maneatingmonkey.ThinkPad E540 NM-A161 _ Rev:1.0
[COLOR="Red"][Mod. Edit-Vesko356] [/COLOR]Files copied from a thread in the Tech Forum
[B]To help other forum members looking for this schematic[/B], not just the OP - maneatingmonkey.ThinkPad E540 NM-A161 _ Rev:1.0
[COLOR="Red"][Mod. Edit-Vesko356] [/COLOR]Files copied...Leave a comment:
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Thinkpad Edge E540 missing PM_SLP_S5# and VM_PWRON
Hi, I'm seeking the knowledge of repair wizards familiar with Thinkpad power on sequences.
The symptoms are that when the power button is pressed, the red light comes on, but there is no other activity.
The +3VALW and +5VALW rails are present, but none of the subsequent voltage come up. No shorts on inductors or anything obvious like that. EC_RSMRST#, PBTN_OUT# and +RTCVCC are all present, but there is no PM_SLP_S5# or later signals.
I also do not get a VM_PWRON signal. I believe this is needed to enable initial power to the BIOS chips, which are not...Last edited by Vesko356; 05-02-2023, 10:19 AM. Reason: Attached schematic and boardview removed and replaced with link. -
What is this component on TV LED backlight strip?
What sort of part is this? Open loop on multimeter. All it says is '4E' and then 'BA' in smaller text vertically. The piece to its left is similar except it says '2' instead of BA has a line indicating polarity.... -
Re: Help identifying 5-pin chip on Soniq main board
I removed the chip and traced the pads on the board with the help of my multimeter. The same colour square indicates a path on the PCB in the photo. Given that pins 1 and 4 of U5 are shorted, that doesn't really fit with the LM3671, but does make sense for something like the M3406, where pins 1 and 4 are Vin and En. FYI the voltage at these points (with the chip removed) is 5.13V....Leave a comment:
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Help identifying 5-pin chip on Soniq main board
Chip U5 on main board LED64801-S1M1A of Soniq E48W13A is clearly blown, but I have no idea what it is. Can't find a schematic anywhere.
I can vaguely make out some remains of letters that look like "D3R8", but I'm not confident that's what it says....Last edited by maneatingmonkey; 03-20-2020, 07:26 AM. -
Re: LED LCD TV Screen Half Black, Half White - Panasonic TH-65AX800A
So now that the short is gone, when I connect the right two buffer boards I now get an image on that half of the screen (instead of solid white). But when I connect the left two buffer boards instead, I now get vertical bars and no picture (instead of solid black).
I actually put back one of the SMD caps, since only the second one I removed was shorted, even though both were in parallel, and it didn't change anything. So I suspect that there is another fault either on the T-Con board, or somewhere...Leave a comment:
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Re: LED LCD TV Screen Half Black, Half White - Panasonic TH-65AX800A
I don't have anything to measure capacitance with :|Leave a comment:
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