Greetings all!
Originally this set had the usual messed up video symptoms such as: horizontal lines, weak, grainy video, bottom and top of picture differ in intensity of problem. It also seemed to slow to turn on or show the messed up picture.
Seemed like must be YScan/buffer board failure. Ordered buffer boards from my distributor which were supposed to be original/new and also from another distributor, I ordered the YSUS because I wanted to replace it for preventative maintenance. (also, the YSUS had a bulged cap, so there was even more reason to suspect it could have even more wrong with it).
Before I replaced the 3 boards, I pulled the power supply and replaced the 2 usual caps C8059, C8060 (3300ufd, 10v). Out of curiosity, I tried the set to see to if it would act differently and to my surprise, it was doing something differently now. Now it would not power up and the front power LED was blinking red 7 times and the green LED on the power supply daughter board was flashing 5 times. I thought, I will wait and replace the YSUS and buffers when they come in and see what happens.
After replacing the YSUS and buffers, the symptom was still the same with the 7 red blinks on the front. With further investigation, I found that if I unplugged the power cable to the YSUS from the power supply, the error blinks would stop and voltages would come up. So I realized YSUS or buffers were an issue.
Pulled the buffers and tested for shorts, none found. What I did realize, was that the buffers definitely didn't look new. The buffer ICs on one of the boards had all been replaced and the solder on the bottom of several of the ICs hadn't flowed through at all except for one hole. Not good looking, but because they didn't test shorted, I moved on. A fellow tech told me the YSUS has an SMD resistor under the heatsink near the buffer connectors that can be tested to see if the YSUS has a definite failure. The resistor (R5063) should be 100k and I found that this one was reading only 50 ohms.
So, i tested the original YSUS and found that this resistor was showing 100k. I replaced the bad cap on this YSUS and installed. Voila! I no longer had the blinking LEDs and shutdown, BUT------after what seemed like a normal power up noise and good buzz from the YSUS (for like 1 second), the YSUS started pulsing that buzzing noise at 1/2 second intervals and the panel was priming over and over again.
I decided to try another "new" YSUS. I returned the YSUS I had ordered and they sent me a new one, installed it and still had the exact same pulsing buzz.
Now this is where I am. I suspect that buffer board, but am not sure. What do you all think?
Here's the voltages currently:
VA:70.0
VG: 15.2
VE: 84.3
VS: 203.9
Vscan: -185.2
On CN1M46 plug:
8.6v line is good
5.2v line is good
12v line is good
Originally this set had the usual messed up video symptoms such as: horizontal lines, weak, grainy video, bottom and top of picture differ in intensity of problem. It also seemed to slow to turn on or show the messed up picture.
Seemed like must be YScan/buffer board failure. Ordered buffer boards from my distributor which were supposed to be original/new and also from another distributor, I ordered the YSUS because I wanted to replace it for preventative maintenance. (also, the YSUS had a bulged cap, so there was even more reason to suspect it could have even more wrong with it).
Before I replaced the 3 boards, I pulled the power supply and replaced the 2 usual caps C8059, C8060 (3300ufd, 10v). Out of curiosity, I tried the set to see to if it would act differently and to my surprise, it was doing something differently now. Now it would not power up and the front power LED was blinking red 7 times and the green LED on the power supply daughter board was flashing 5 times. I thought, I will wait and replace the YSUS and buffers when they come in and see what happens.
After replacing the YSUS and buffers, the symptom was still the same with the 7 red blinks on the front. With further investigation, I found that if I unplugged the power cable to the YSUS from the power supply, the error blinks would stop and voltages would come up. So I realized YSUS or buffers were an issue.
Pulled the buffers and tested for shorts, none found. What I did realize, was that the buffers definitely didn't look new. The buffer ICs on one of the boards had all been replaced and the solder on the bottom of several of the ICs hadn't flowed through at all except for one hole. Not good looking, but because they didn't test shorted, I moved on. A fellow tech told me the YSUS has an SMD resistor under the heatsink near the buffer connectors that can be tested to see if the YSUS has a definite failure. The resistor (R5063) should be 100k and I found that this one was reading only 50 ohms.
So, i tested the original YSUS and found that this resistor was showing 100k. I replaced the bad cap on this YSUS and installed. Voila! I no longer had the blinking LEDs and shutdown, BUT------after what seemed like a normal power up noise and good buzz from the YSUS (for like 1 second), the YSUS started pulsing that buzzing noise at 1/2 second intervals and the panel was priming over and over again.
I decided to try another "new" YSUS. I returned the YSUS I had ordered and they sent me a new one, installed it and still had the exact same pulsing buzz.
Now this is where I am. I suspect that buffer board, but am not sure. What do you all think?
Here's the voltages currently:
VA:70.0
VG: 15.2
VE: 84.3
VS: 203.9
Vscan: -185.2
On CN1M46 plug:
8.6v line is good
5.2v line is good
12v line is good
Attached Files
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