My latest project is a Samsung LN-T3753H. This TV has distorted colors. The best way I can think to describe it is it looks like the picture is being displayed using a couple dozen colors instead of the usual millions. (Think of a JPG dithered down to a GIF or 16-color BMP, something like that). However, the onscreen menus are displayed without issue.
Searching on the Internet this is a fairly common problem with Samsung TVs, but no one seems to have found the problem. Most people give up and replace entire boards. The general consensus is the problem is most likely on the main...
Freezer
Senior Member
Last Activity: 10-07-2022, 10:50 AM
Joined: 06-10-2010
Location:
-
Re: Dell Studio One 1909 - 5 seconds to black
I'm back from my trip and I've had a chance to look at this panel. Before disassembling the LCD panel I told myself if the problem was bad solder joints I would try and repair, but if the problem was a bad CCFL tube I would not try and repair it even though you can buy replacement CCFLs. The reason for this is simple. The replacement CCFL plus s/h would run about $20 for a single tube, but on eBay brand new replacement panels cost between $40 and $50 shipped. And the downside to replacing the CCFL is I may spend the $20 to buy the parts... -
Re: Dell Studio One 1909 - 5 seconds to black
I connected some known good CCFLs to the defective monitor. This test allowed me to confirm the inverter board is good. Also, through a process of elimination I can say the problem is the lower CCFL. The upper CCFL works fine.
Now I know where to focus my efforts. When I get a chance I need to remove all the computer parts and get the panel out. This will be my first attempted disassembly of an LCD panel - but I feel up to the challenge. Unfortunately I'm leaving for a long vacation soon, so I'll have to wait 2 weeks or...Leave a comment:
-
Dell Studio One 1909 - 5 seconds to black
My latest project is a Dell Studio One 1909, it's a 19" all-in-one computer/monitor. The problem is when you turn it on the screen comes up for about 5 seconds and then goes black. If you connect an external monitor the system works fine, so I know the problem isn't the computer side of things. If I shine a flashlight into the screen after it goes black I can still see the image. So the problem is the CCFL backlights.
Taking the back off I first looked at all the caps, especially those on the power supply and inverter boards (less concerned with the caps on the computer motherboard).... -
Re: HP 2509m won't turn on, no power to ON/OFF LED
It's been several weeks, but I finally got time to work on this monitor. The short answer is - the repair was successful! After opening the monitor I first performed a visual inspection and tested the ESR of the caps - no problems found. So I desoldered the little daughter board to test the problematic MOSFETs and diode. Testing in circuit I'm pretty sure the diode and N-channel MOSFET were bad. After desoldering and retesting, the diode and N-channel were most definitely bad. The P-channel was probably good, but I went ahead and...Leave a comment:
-
Re: HP 2509m won't turn on, no power to ON/OFF LED
A good friend of mine is an electrical engineer so I asked his input. He said if I could tell him the part number of the driver IC he could analyze the circuit and find MOSFETs that fit the circuit, which would be easier than trying to find a replacement for the existing MOSFETs. Unfortunately, I'm unable to find a datasheet for the driver IC (I don't have the IC part number in with me, but I believe it's in this thread). But he did his best to find replacement MOSFETs.
For the N-channel he selected the STD20NF06LT4,...Leave a comment:
-
Re: HP 2509m won't turn on, no power to ON/OFF LED
Thanks for the quick reply. Applying your info to my digikey searches I get the following for the N-channel MOSFET:
Original P5506BDG:
V(br)dss = 60V
Rds(on) = 55mohms
Id = 22A
Vgs = +/-20V
Pd = 50W
Vgs(th) = min=1V, max=2.5V
Ciss=587pF
STD16NF06LT4:
V(br)dss = 60V
Rds(on) = [B]70mohms[/B]
Id = [B]24A[/B]
Vgs = [B]+/-18V[/B]
Pd = [B]40W[/B]
Vgs(th) = min=1V, [B]max=? (datasheet does not specify)[/B]...Leave a comment:
-
Re: HP 2509m won't turn on, no power to ON/OFF LED
I recently picked up a broken 2509m off craigslist which does not power on at all. I'm still diagnosing the problem, but I suspect the problem is the 2 mosfets and the diode everyone speaks of in this and other threads about this monitor. As others have noted, these 2 mosfets are no longer available, so most people resort to buying high priced "originals" off ebay from China. But who's to say the quality of these. I'm hoping to find suitable replacements on digikey. I know how to select replacement caps, but mosfets are...Leave a comment:
-
Re: Clearing plugged holes
Success!
Most seem to suggest poking the holes free with something like a dental pick. I don't have a dental pick (although I'm definitely going to add some to my tool box). But I found a sewing pin was just the right size for the holes. Using my iron I heated up the joint and once melted I slowly worked the pin through the hole. It took between 15 and 30 seconds of heating per hole. Once the pin was through I kept the pin moving as I removed the iron (to prevent the solder from bonding to the pin).
Thanks to all for the suggestions....Leave a comment:
-
Clearing plugged holes
I'm looking for advice from anyone who's dealt with this problem before. I have a computer video card with 4 blown capacitors. Last night I desoldered the capacitors, but most of the holes (vias) are still plugged with solder and I've been unable to clear them. It's this darn lead-free solder combined with a multilayer board and large ground planes. Here's what I tried last night.
1. Holding my iron on the via to melt the solder, then hitting it with a Soldapullt solder sucker.
2. Using desolder wick to suck up the solder.
3. Adding fresh leaded solder and/or...Last edited by Freezer; 01-24-2014, 04:22 PM. -
Where to buy replacement "rubber bands?"
Quick question I'm hoping someone will know the answer to. I have a CD player I need to repair. It has a motorized door, but the door no longer opens or closes on its own. The problem is the "rubber band" that goes from the motor to the pulley on another shaft has stretched out over time. Where can you buy replacement parts like this? I've searched Digikey, Mouser, and Jameco - I can't find this type of replacement part anywhere. Part of the problem is I don't know what the technical term would be. I've tried searching for "band" and "belt" neither of which turned... -
Re: Sony KV-34HS420, blinking standby light
I think I can answer my own question here. If you read the service manual for this (or other similar Sony CRT TVs) they have 3 areas to check; cable dressing, physical calibration, and electrical calibration.
[B]1. Cable Dressing[/B]
Since CRTs generate magnetic fields and have really high voltages in them, the placement of certain wires inside the set can negatively impact the image. To remove the board and solder in the new parts you have to disconnect some wires and move others. So make sure to follow the cable...Leave a comment:
-
Re: ViewSonic n2750w - weird image distortion
I guess it could be the T-con board, but since the on-screen display has absolutely no image distortion, I'm assuming the problem is somewhere on the main video board. But I am out of ideas on the main video board so it never hurts to check the T-con board....Leave a comment:
-
Sony KV-34HS420, blinking standby light
I have a Sony KV-34HS420 with blinking standby light. This TV is a widescreen CRT with full 1080 resolution and HDMI input. I personally think the image is as good as any LCD or plasma. The problem is the set won't turn on. When you apply power the standby light on the front starts flashing. Most of the time it flashes 6 times, but sometimes it flashes 7, and one time it flashed 4.
I know this era Sony TVs has a systemic problem with two ICs on the DZ board. The replacement part is the MCZ3001DB, easy to find on eBay. These chips are marked "A" in the attached picture.... -
Re: ViewSonic n2750w - weird image distortion
I ordered a replacement voltage regulator from digikey. Every replacement part had the input and output pins reversed from the one in this TV. So I ended up soldering in the part backwards and connected the pins with wires (see picture). Now the voltage is down to 7.9 which is much better. However, the TV still has the image distortion.
I decided to replace more of the bad caps. The first cap I replaced was connected to a huge ground plane which made it difficult to remove. So I replaced all the bad caps that were easy...Leave a comment:
-
Magnavox 37MF231D/37
A few weeks ago I was at yard sale and they were selling a broken 37" flat panel TV (Magnavox 37MF231D/37). The screen was fine (no cracks), so I suspect the problem is power board related. I talked them down to $10 which seemed like a good price to me.
The back comes off pretty easy, just a bunch of screws around the edge. Once open, a few more screws and you can release the cage holding the power and video boards.
After removing the power board I see one obvious problem. Cap C2074 (2200uf/25V) is bulging. The power board only has 7 caps (not counting the big... -
Re: ViewSonic n2750w - weird image distortion
No I didn't get a new meter, I guess the problem is I have an old brain.
I looked at the piece of paper where I jotted down the numbers and I can totally see how I thought some scribbles were numbers. Since I made that mistake, I went back and took all new set of readings. Everything was the same as what I reported above. For the 12.XXX readings, just drop the last digit.
As for I139, I'm definitely getting 8.7V from pin 1 and 12V from pin 3, which doesn't make sense when you look at the datasheet. So...Leave a comment:
-
Re: Hanns-G HQ191DP - no power
The sticker on the back says January 2007 - so about 5 years old. That seems to be about the norm, most TVs and monitors I work on are about 5 years old. Sadly, if you get more than 5 years out of a new monitor or TV then I think you're doing good. Gone are the days of TVs lasting 20 years....
Leave a comment:
-
Hanns-G HQ191DP - no power
I recently picked up 4 broken monitors on craigslist, one of which was a Hanns-G HQ191DP. It's a 19" monitor with DVI and VGA inputs, audio input with built-in speakers, and CCFL backlights.
To open the monitor start by removing the stand and all the screws on the back. The next step is to pry the two pieces apart. This proved to be more difficult that most monitors. For some reason the bottom of the monitor was really difficult, there were times when I felt like I was going to break the plastic. Once you get the monitor apart you can access the metal cage on the back with... -
Re: ViewSonic n2750w - weird image distortion
Sorry it took so long to reply on this thread, I was on vacation.
retiredcaps - I've had a chance to get the voltage readings you requested. I have the service manual, so instead of trying to read part numbers off of chips I grabbed the part number from the service manual.
Chip: I101
Part: SI-8050SD 5V/3A
pin1: 12.073
pin2: 5.097
pin3: 0
pin4: 4.964
pin5: 2.370
Chip: I103
Part: SI-8050SD 5V/3A
pin1: 12.081
pin2: 5.033
pin3:...Leave a comment:
No activity results to display
Leave a comment: