I thought I did and didn't find anything out of the ordinary. But maybe I didn't?
Thank you!
Joe
cajoeg
TV_Newbie
Last Activity: 03-17-2025, 10:20 PM
Joined: 02-06-2025
Location: Yucaipa, CA
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[B]SOLVED!!![/B] My first TV repair!
It was the Aluminum Organic Polymer Capacitor at C930 (680 10v). I replaced it this morning, and the TV came up immediately.
Thank you to everyone for your guidance and help!
Joe[B]SOLVED!!![/B] My first TV repair!
It was the Aluminum Organic Polymer Capacitor at C930 (680 10v). I replaced it this morning, and the TV came up immediately.
Thank you to everyone for your guidance and help!
JoeLeave a comment:
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Last night I used the schematics to trace pin 4 (DIM) and pin 10 (ON/OFF) on the OZ9923 chip to see if any issues existed. I found no issues (shorts). Today I printed out the datasheet for the OZ9938 chip to learn more about the function of the other pins on the chip. Chip pins 5 and 6 deal with current/voltage sense feedback. It seems (logically only) as if the chip is not getting the feedback from the mainboard on the +5v lines. So I did some tracing of the +5v lines. All three +5v lines go back to the capacitor at C930, one of the Aluminum Organic Polymer Capacitors I have yet to replace. The...Leave a comment:
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I just repeated the testing. On the bad board, the "plugged in" readings were the same as before, 0 (zero) on both the DIM and ON/OFF pins. But, the resting readings (after pressing the ON button) for the DIM and ON/OFF pins are 0 (zero) on both now. This is a change on the DIM pin as it had a resting read of 1.58v after the first test. I tested each pin individually with the board plugged in, and then pressing the ON button. The +5v pins and +12v had the same results as before.
On the good board, nothing has changed as far as readings. Everything works great.
...Leave a comment:
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Thank you for your reply. I will redo the solder joints as you suggested.
As for the testing, what you're recommending is actually exactly what I did to get the aforementioned measurements. I had the negative probe on ground, positive on the respective pin such as DIM or ON/OFF. While plugged in but not on, I took a read. Then I pressed the ON button and took a reading while the TV was trying to come up. I left the positive probe on the respective pin and took it's resting reading. I did not press the ON button again until I changed which pin I was testing.
But it's worth...Leave a comment:
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I took the time to install the good power board into the working TV and take power reads at the Main Board connector. I checked the power when "Plugged In", "Power On", "Mid Read" (if any), and "Resting Read". I then did the same with the bad power board installed. Below are the results. Notice the differences of the following - DIM, ON/OFF, all three +5v, and the two +12v reads (not that bad?). Something is pulling down the +5v, and messing with the DIM as well.
[ATTACH=JSON]{"data-align":"none","data-size":"custom","height":"544","width":"673","data-attachmentid":3586806}[/ATTACH]...Leave a comment:
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Thank you for the great schematic version! Much better, and easier to read. It's also accurate versus the service manual.
I'm still trying to find the issue. Everything I've tested so far seems to test just fine when using the working power board as a baseline comparison for measurements. But I'm a patient learner, and realize that I will make mistakes as well. I also don't quit. I'll find it somewhere.
JoeLeave a comment:
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The optocoupler turned out to be fine.
I took the power board out of an identical working TV, and inserted the one I'm working on. The good TV did verify that it's a faulty power board. I did several measurements, and I can't find any difference as off yet. But, going back to testing the Stand-by voltage, I apparently measured the wrong wire. There is no clearly marked STANDBY pin on the connector. I used the DIM wire which appears to be incorrect, unless it is also used as a STANDBY.
Here's the pinout for the connector from top to bottom:
Pin 11: +12V
Pin...Leave a comment:
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Long story short, I got the new part in, and it also has continuity even before I installed it. I tried it anyways, and the LED quit working all together. So I put the old part back, and the LED came back. So I'm back to where I was before. I have not replaced the bridge rectifier.
In watching other power board repair videos, one mentioned the optocoupler and its role. So I looked up a video on how to test a optocoupler, and found this one:
[URL]https://www.youtube.com/watch?v=g7ZVk78MR7k[/URL]
Per the video, putting the multimeter in diode mode, placing the red...Leave a comment:
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I was about to test all of the capacitors, but while watching the video on testing the bridge rectifier, that other video listed on the right side of the YouTube screen caught my eye.
No short at Q901. I will put the good bridge rectifier back in since my new ones will not arrive until just before mid-March. The new resistors are expected to arrive on 2/20/2025.
Thanks for the tips!
Joe...Leave a comment:
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Before I started testing the other capacitors, I saw this video on YouTube where the technique used to isolate the fault(s) on a TV gave me the idea to quickly check for a short:
[URL]https://www.youtube.com/watch?v=kallk3Kcbp0[/URL]
I found a short at a resistor near the bridge rectifier. I got continuity on the resistor each time I checked it. Today, I removed the resistor and checked it again. It still has continuity. It's a 39 Ohm Resistor, 2W 5%. Of course I didn't have one in stock, so I ordered one. Here's a photo of the power board and the associated resistor:...Leave a comment:
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Okay, back at it while the wife took the grandchildren to a park for a a few hours.
I replaced four capacitors on the power board. I attached a photo showing the four I replaced that have a blue dot on them (used MS Paint to apply dots in photo). Even though they tested good, I replaced them. There's a very large capacitor that tested good while still on the board. I reinstalled the board and tried to power up again. I didn't expect any change, and there isn't any. Still flashes the LED.
There's also two components that I don't know what they are. I circled them with...Leave a comment:
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Yes. Below is a image of the mainboard. I agree that the so-called "working" mainboard likely has the same age components.The seller stated that it came from a working unit with a broken screen, and that their technicians tested it. For $25 plus shipping, I had to take a chance.
I just now tested a few capacitors on the extra mainboard using that method, and they show that they are good. Interesting method! Unfortunately, I put the TV back together in anticipation of waiting for the new capacitors to arrive, I also am cleaning up my den from the recently acquired TRS-80...Leave a comment:
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Thank you. I replaced two of them as of this morning. The other I had to order. I retested after replacing the two capacitors, and the TV still has the same issue. I'll keep going until I find the culprit(s).
Joe...Leave a comment:
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Thank you! I'd rather just replace capacitors. I have plenty in stock, and it's fairly easy to do.
Just to make sure, we're both talking about the capacitors on the power board, correct?
Thanks again!
Joe...Leave a comment:
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I took out the power board and checked it over. I found nothing obvious. I even checked some of the traces for the on/off wire connector back to the IC on the board. As a second test, I took out the main board and installed the replacement main board I had purchased that was sold as being tested and good. It also provides the same test results. Perhaps I need to replace that capacitors on the power board?Leave a comment:
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I have strike two! Sorry, learning from ground zero. I do greatly appreciate your patience and guidance.
I did use the technique shown in the video by leaving the connectors attached. I did this three times. When the TV off, I had no reading. When I pressed the power button, it briefly read 1.27V and then that went away. The subsequent tests showed even lower reading in decreasing order down to 0.3V.
I'm going to remove the power board and take a look at it.
Thank you very much!
Joe...Leave a comment:
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D'oh! I double checked the letter, but not the number.
Below is a photo of the connector I did the testing on directly with the other end connected to the power board. The top two wires are +12v (black & white), the next two are GND (gray & purple), the next three are +5 (blue, green, yellow), the next two are GND (orange.& red), the next one is NF (brown), the next one after that is not connected, and the last wire is on/off (black).
During the testing of the on/off, I got no reading with the TV in standby mode, and no reading for when the power button was...Leave a comment:
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Thank you for the prompt reply! I did retest the bridge rectifier (I actually forgot that I learned how to test a while back). It's fine.
Now, since I'm still learning, please see the attached photo and let me know which pin inside the connector on the top should I connect to with the positive probe. The pink wire pin on top, or the white one below it? I tried to see if either was ground via continuity test, but got nothing.
[ATTACH=JSON]{"data-align":"none","data-size":"full","title":"IMG_2580.jpg","data-attachmentid":3568822}[/ATTACH]...Leave a comment:
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Insignia NS-LCD019-09 issue: Power light turns blue for 3 seconds, the flashes red before going solid read again
Hello, I'm new to the group and to trying to repair a LCD TV. During the past few years, I've been collecting/repairing/restoring vintage personal computers (Commodore, Apple II, Atari, TRS-80, Texas Instruments, and Timex Sinclair). This has been my retirement hobby. Now I've gotten interested in trying to repair a LCD TV that I have and used regularly when working on vintage computers.
The LCD I'm working on is a Insignia NS-LCD019. I've downloaded the service manual that I could find, but it must be a different revision since not too many items in the service manual match the TV...
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