Re: Using a resistor to fake a Inverter into thinking a CCFL is good
After 20 days, the LED kit arrived from China.
Initially I hooked up the LED driver board (GYD-9E with its DF6113 chip) to a 10 volt battery and applied 3 volts DC to the enable wire. The LED turned on but the current drawn from the battery was only 25 ma. I added another 5 volts DC in series with the 10 volt battery to give me 15 volts and the LEDs went brighter and the current draw was now up at 0.4 amps, so the lights were now drawing 6 watts.
There was no sticky tape on the back of...
montreal
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Last Activity: 11-09-2017, 11:39 AM
Joined: 09-02-2010
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Re: Using a resistor to fake a Inverter into thinking a CCFL is good
I suspect that each LED chip draws 60 milliwatts. And from the advertisement photo, there appears to be about 2 per inch, so for my 19 inches, that's about 2.5 watts. This compares to 2 CCFL lamps in the same space generating about 12 watts. The metal U shaped reflector will pick up some of the heat from the LED strip and it is touching the metal rear shell of the panel, so I might coat the places where metal touches metal with heat sink grease to improve the thermal conductivity.
The...Last edited by montreal; 10-19-2017, 07:42 PM.Leave a comment:
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Re: Using a resistor to fake a Inverter into thinking a CCFL is good
I found that my lamps are very thin, as two are crammed into 6 millimeters of width within the metal "U" shaped reflector. The bulbs are very difficult to separate from the metal case without cutting the low voltage wires. They feel as fragile as a thick piece of spaghetti.
I called a few stores which specialize in recycled computers and none keep broken panels around for spare parts.
Today I ordered a LED conversion kit from China via Ebay for under $12 US with...Last edited by montreal; 10-19-2017, 06:01 PM.Leave a comment:
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Re: Using a resistor to fake a Inverter into thinking a CCFL is good
Good news and bad news.
First the good news: After looking at a few Youtube videos showing how panels identical or similar to mine are disassembled, I partially disassembled mine. After I turned off all the background noise in my workshop, I could hear some arcing noise when the CCFLs fired up. As I had removed my grounding resistor to pin 1, the protection circuit shutdown the lamps after 2 seconds. I decided to completely disassemble the whole panel which exposed the top and bottom lamp assemblies....Leave a comment:
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Re: Using a resistor to fake a Inverter into thinking a CCFL is good
Thanks for your idea, but I don't have enough room to hide a T5 4W.
It would be very easy to prevent the detection circuit attached to pin 3 from sensing that lamp number 4 is drawing less current than desired. I just have to remove R219 and that way, one leg of D202 would float.
I know that my lamp number 4 draws less current than it should, but I don't think it is drawing no current at all because one time in fifty, when I turn on the monitor, the panel does not shut down...Last edited by montreal; 10-17-2017, 10:18 PM.Leave a comment:
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Re: Using a resistor to fake a Inverter into thinking a CCFL is good
Here is a photo of the back of my panel.
Attached is the spec for my M220EW01 panel.
I appreciate better what you were saying about the dynamic resistance of the CCFL.
For the SEM2005 chip to believe that a healthy CCFL is in place when in fact there is a substitute fixed resistor, then the resistor will have to mimic the characteristics of the CCFL if detection circuit is to function properly and the transformer is to see the same load as a real CCFL....Leave a comment:
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Re: Using a resistor to fake a Inverter into thinking a CCFL is good
P=I x I x R
or
R = P / (I x I)
R = 6 watts / (0.0015 x 0.0015) = 2,727,273 ohms
V - I x R = 0.0015 x 2727273 =4091 volts, so you are correct.
The average current through R221 is probably much less than 1.5 ma. and likewise the average voltage across the CCFL, however to get the 1.85 volts DC held across C214 which I was reading today, the peak current through R221 had to have been 2 ma, meaning 1.5 ma rms, and a peak lamp voltage of...Last edited by montreal; 10-16-2017, 11:22 PM.Leave a comment:
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Re: Using a resistor to fake a Inverter into thinking a CCFL is good
Hi, my Samsung 226BW recently acquired the "2 seconds to black screen" syndrome and after exhaustive analysis, I concluded that one of the four CCFL lamps was drawing too little current to satisfy the detection circuit (SEM2005 chip)
Once I realized that pin 3 of this chip was upset because the input voltage there was at 1.18 volts instead of the minimum of 1.3 volts, all I had to do was determine which of the 4 cathodes belonging to the 2 diode pairs D201 and D202 was the origin of the...Last edited by montreal; 10-16-2017, 11:19 AM.Leave a comment:
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Re: Samsung 226BW - blue power light stays off
Samsung has authorized a number of agencies around the world to repair their products, not just their own warranty service depot. Any authorized service depot could have temporarily replaced the bulging caps in my monitor before determining that the caps were not the cause of the continuing fault.
I put back all the original Samsung capacitors on my IP board and the Samsung warranty technician will readily observe that they are bulging and therefore their product is suspect.
Different jurisdictions...Last edited by montreal; 09-09-2010, 12:59 PM.Leave a comment:
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Re: Samsung 226BW - blue power light stays off
As a last effort before giving up, I temporarily soldered a 100 microfarad capacitor in parallel with each electrolytic cap on the logic board in order to provide extra filtering in case any one cap was marginal.
That did not improve things so I came to the conclusion that whatever is wrong with the logic board, it is probably within the scaler or one of the two eeproms or with the flash memory.
I could never find the perfect schematic for my particular version of the 226BW. The best I could do was find...Leave a comment:
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Re: Samsung 266BW - blue power light stays off
Thanks Solder Boy for the reply.
My blue light gets its power from the logic board. It actually gets 1.8 volts directly from the scaler chip (pin number 123). The scaler chip is fed at many pins by two sources providing 1.8 and 3.3 volts. 1.8 volts is not enough to make the blue light glow. I suspect it needs closer to 3 Volts.
There are 6 push buttons on the front panel including the power-on switch. These buttons are connected to two quad state lines which connect directly to pins 119...Leave a comment:
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Re: Samsung 245 BN44-00195A Supply
My IP board uses a full wave rectifier bridge to charge up the inverter capacitor. Since my line voltage is 120 VAC for North America, and the peak voltage is about 1.5 times that, it is normal to find about 170 volts DC in this can. Because the bridge is full wave, the peak voltage across the cap should never be more than 170 volts DC.
In Europe with 220 Volts AC as the line voltage, 1.5 times that would be 330 VDC on the same can and an electrolytic with a 400 volt rating should be a comfortable fit.
I have seen some...Leave a comment:
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Re: Samsung 266BW - blue power light stays off
Please note that my monitor is the 226BW, my typo incorrectly said 266BW.
Thanks for the prompt to post photos.
I took some photos today of the front side and rear side of both the power-inverter board and the video board.
After digging up some Samsung schematics for closely related monitors, I confirmed that the only voltage produced by the IP board is 14 volts DC and the video board is correctly generating the 5, 3.3 and 1.8 volts DC. All these voltages are available at the various...Last edited by montreal; 09-07-2010, 03:58 PM.Leave a comment:
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Re: Samsung 266BW - blue power light stays off
Thanks for your encouragement on my problem. Since posting, I have examined the video board and identified the DC to DC converter chip that transforms 14 VDC to 5VDC. Next week I will have a chance to see exactly where the 5 volts is not coming through.
As for the missing blue LED power light, there appears to be two surface mounted LED diodes the size of pin heads soldered to the small circuit board that carries the ON/OFF pushbutton. Much smaller than a typical LED, these compact structures are a minimalist solution....Leave a comment:
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Samsung 266BW - blue power light stays off
Hello, this is my first post and any feedback on my problem will be greatly appreciated.
My neighbor gave me his 2 year old Samsung 226BW after it died completely on him a few months ago. Having been an electronics hobbiest for some time, I welcomed the chance to try to give it a new life.
I found that the monitor would have a black screen even though the blue power light was on.
If I disconnected the computer video cable (DVI) and left the monitor attached to the 120 volt AC, then after about 30 minutes I would finally get that moving message on the screen...Last edited by montreal; 09-02-2010, 03:57 PM.
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