How to Fix No Display in Samsung LED TV CM501 IC VGH Missing
How to fix a display in a Samsung LED TV. I came to this Samsung model number UA32F4100R for repair due to a blank screen fault. Its backlight was on and there was also a sound, meaning that its panel was faulty. Now what was the fault in the panel will be known only after diagnosing it. I took the time from the customer and came to fix this set on the next day.
Fault Finding in CM501 DC to DC IC
The next day I opened this TV in the workshop lab and started searching for the fault by opening its panel. I checked the DC to DC voltage of this panel, and its AVDD was 17 volts. After that I checked its VGL voltage, and it was also fine. Its VGH voltage was missing. This was the reason for the blank screen. In this set of DC to DC IC CM501 is used; hence, the VGH voltage was not coming out.
- Opened the TV and started fault finding.
- Found a fault in the DC to DC IC (CM501).
- VGH output was missing.
How CM501 IC Works in Samsung LED TV Panel?
CM 501 IC has VGH voltage coming out from pin number 40. Its pin number 39 is VGH pulse. This voltage is boosted by connecting a double diode from pin number 36. Its input pin source is AVDD voltage. In my case, this VGH voltage was not coming out. When I carefully examined this area of the IC with a magnifying glass, I saw corrosion between the pins here.
- CM501 IC provides VGH voltage from pin 40, and pin 39 is the VGH pulse.
- A double diode connected to pin 36 boosts this voltage, with AVDD as the input source.
- In this case, VGH voltage was missing.
- On close inspection with a magnifying glass, corrosion was found between the IC pins.
How to Fix CM501 IC VGH Fault Repair?
I removed the DC to DC IC and washed it thoroughly, and I also cleaned the PCB and reinstalled the same IC with utmost care. After installing the IC, I checked the entire circuit once again, and the diode that boosts the voltage was separated from the circuit, and I checked it, and it was absolutely perfect. Now I switched on the set and checked the VGH voltage, and it started generating twenty-six volts. When I looked at the screen, the picture was absolutely accurate.
- Removed the DC to DC IC, cleaned it thoroughly, and reinstalled it carefully.
- Checked the entire circuit again; the boosting diode was tested separately and found perfect.
- Powered on the TV and verified the VGH voltage, which generated 26V.
- Screen displayed a perfect picture after repair.
Summary of CM501 IC VGH Fault Solution
You see, we repaired a Samsung LED model that was having a blank screen problem, and we fixed this fault by cleaning the DC to DC IC in the panel area. This DC-to-DC IC was having a problem due to corrosion and was not generating VGH voltage, so we cleaned it. After cleaning it, we reinstalled it, and our circuit started working perfectly, so I requested my technician to do chip-level work. Maybe you can do it; work hard.
- You see, we repaired a Samsung LED model that was having a blank screen problem, and we fixed this fault by cleaning the DC to DC IC in the panel area. This DC-to-DC IC was having a problem due to corrosion and was not generating VGH voltage, so we cleaned it. After cleaning it, we reinstalled it, and our circuit started working perfectly, so I requested my technician to do chip-level work. Maybe you can do it; work hard.
FAQ Section
Q1: What are the symptoms when VGH voltage is missing in LED TV panel?
A1: VGH is missing, blank screen, sometimes blue screen after lines appear, depending on which panel it is.
Q2: How to test if CM501 IC is faulty in a Samsung LED TV panel?
A2: Check the voltage on pin 40 of the IC. Check the diode and related parts outside the IC.
Q3: Can a LED TV show backlight but no image because of VGH missing?
A3: If the panel has a side COF, check the VGH voltage at the corresponding point on the side COF.
Q4: How to repair CM501 IC when VGH voltage is not present?
A4: Read the content given in this article. If the fault still does not get fixed, replace the IC.
If you want to read the complete article on how to fix Samsung TV automatic volume increase, click here.
Shaukat Ali has over 30 years of experience in LED TV repair, specializing in chip-level repair work. He is an expert in Sony LED TVs, and also repairs other major brands like Samsung, TCL, Orient, and Haier. His expertise includes display panel faults, motherboard issues, power supply circuits, T-Con, and HDMI faults. Based in Lahore, he shares real-time fault finding cases from daily repair work to help technicians and learners with practical experience.
📞 Contact: +92 321 4066054
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