Re: Samsung PN50C450 YSUS Board Diagnosing Help
Do you know where I can get a replacement part for cheap. The part is not expensive but shipping it sure is. Do you have a part number for a replacement. I have been looking at the TDK FG26X7R1E106KRT00. I am assuming a 25V cap is ok....
jimg1948
Member
Last Activity: 09-19-2017, 01:11 PM
Joined: 03-10-2014
Location: andover, massachusetts
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Re: Samsung PN50C450 YSUS Board Diagnosing Help
Just to help others that may encounter a short across the opto-isolaters I thought I would provide an update on my progress. I took a brute force method an started cutting each part out until I found the bad part. I started with the opto's, transistors, and then caps. Murphy's law took place and it was the last part selected. It was a blue ceramic capacitor the was causing a 4 ohm resistance across the opto. It was a 10uf 25v capacitor with board marking c5403. Hope this might help others with the same problem.Leave a comment:
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Samsung PN50C450 YSUS Board Diagnosing Help
I have a Samsung PN50C450B1D that would not power up. The LED on logic board blinked 5 seconds on and 2 off. This indicates that the problem is on YSUS or XSUS board. Y Buffer board tested fine. Ordered used YSUS(LJ92-01728C) and Y Buffer Board(LJ92-01729A). Installed both and TV works fine. While waiting for boards, I started to diagnose the problem on YSUS board. I would like to fix and keep as a spare in case the board I bought craps out. IGBTs and power diodes all seem to check out fine. While probing resistances on the board I found a low resistance (4 Ohms) between pins 4(VCC) and 6(Float... -
Re: Vizio M261VP Powers On Has Sound But No Video
Success of sorts
I noticed if I pressed on the display board the voltages would stabilize and the abnormalities in the video would disappear. I made a clamp and attached it under an LCD mount screw to hold the board tight. TV has run for a couple of hours without any problems. Can not guarantee how long it is going to last but at least it is ok for now.Leave a comment:
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Re: Vizio M261VP Powers On Has Sound But No Video
Thanks
I found that the Vs (Pin 19) connection to the BUF08832 chip also exhibited unstable voltage (around 11.0-15.2V). I was able to trace that back to the MAX17113 power supply chip on the positive-charge pump regulator circuit (pin 2 DRVP). This pin is connected to a capacitor and dual diode. One side of the dual diode produces the AVDD 15.2V voltage and the other side the VGH 25.2V voltage. Both voltages are intermittently unstable. I found if I lay the TV flat on its face the voltages stabilize to 15.2V AVDD...Leave a comment:
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Re: Vizio M261VP Powers On Has Sound But No Video
I find a VDD =15.2V and a HVDD = 7.5V. Is HVDD the same as AVDD?
Where would I find AVDD?Leave a comment:
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Re: Vizio M261VP Powers On Has Sound But No Video
I checked the voltages on the display board. The following is what I found.
Vcc = 2.75V no ripple (this is where bad cap was removed)
Vgh = 25.7V
Vgl = -7.5V
DPV = 2.5V
POL = 1.4V
SOE = 0.2V
VcomL = 4.0-5.5V
VcomR = 4.0-5.5V
VcomRFB = 4.0-5.5V
VcomLFB = 4.0-5.5V
Vcc seems a little low. I expected around 3.3V. It is still within the operating range of the chips that use the voltage.
The 1.5V swing on the Vcom voltages was not...Leave a comment:
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Re: Vizio M261VP Powers On Has Sound But No Video
I think it is a ceramic. It is an 0805 size SMD but is unmarked.
This capacitor according to the MAX17113 datasheet is to minimize ripple. It looks like a value from 10-22uf would work ok. The higher the capacitance the lower the ripple. ESR also contributes to the ripple and that has to be less than 43 milliohm. It is connected to the output side of a 10uH coil and ground. There are a couple of other caps downstream to ground so I did not think it would hurt to run the tv without the shorted cap until I could buy...Leave a comment:
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Re: Vizio M261VP Powers On Has Sound But No Video
I thought I would post a progress update on diagnosing no video problem in case anyone has the same problem in the future. I removed what I thought was a shorted Schottky diode from the video display board power supply. To my surprise The short was still in the circuit. the diode checked ok. So after more diagnoses I determined bypass capacitor C71 on the display board (t-con) was causing the problem. Removed the capacitor from the circuit and the short disappeared. Reassembled the set without the bypass capacitor and I now get video....Leave a comment:
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Re: Vizio M261VP Powers On Has Sound But No Video
Thought I would post update on diagnosing no video on M261VP. Since audio and other functionality of the main board seem to be working ok I decided to focus my attention on the T-con board. The T-con board is getting the 12Vdc source voltage ok from the main board. The board has additional power supply components to get the proper voltages to drive the LCD display. 2 chips appear to be doing most of the power conversion the first is a TPS62110 17-V, 1.5-A, SYNCHRONOUS STEP-DOWN CONVERTER and the second is a Maxim 17113E (US1) Low-Cost,...Leave a comment:
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Re: Vizio M261VP Powers On Has Sound But No Video
Pretty sure the power adapter is ok because it powers up the tv and I measure the 19v with the TV on. This problem is somewhere in the video processing. Either on the main board or the display board. I checked the ac ripple as you suggested and none was detected.Leave a comment:
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Vizio M261VP Powers On Has Sound But No Video
I have a Vizio M261VP 26" LED/LCD HDTV that will turn on/off and has sound but no video. The LED backlight lights bright and then dims to about half the brightness after 5-10 seconds. There is no video and I can not see the menu when selected.
The TV is powered from a 19Vdc AC/DC Adapter that checks ok.
There are basically only 2 boards in this tv. See attached pictures. The main board part number is 3626-0082-0150(3E)). It contains all power supply circuitry (including for the LED Backlight), audio circuits, video circuits, and all external input ports. The... -
Re: New Members - please post your introductions here
Hi Everyone.
I am a newbie to this forum. I am a retired electronics engineer with over 30 years experience in computer systems. I have been an electronics/computer hobbyist since the early 70's. First computer was a Radio Shack TRS-80 Model 1 with 16KB RAM and a tape recorder for program input. We have come a long way since then. I have been fixing TVs and Radios since the tube days where my father and I would spend long hours in the cellar swapping tubes.
Hope I can receive the help I need and...Leave a comment:
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