42pfl7422d/37 won't power up
I'm a newbie, and I think I imposed on someone elses thread (afrelientk 42pfl7422d/37 help), sorry because I didn't know how to create a new thread, so now I will recap my problem here. I have a 42pfl7422d/37 no picture no sound. When I turn it on, the relay clicks, the blue power LED comes on but no picture or sound. After about 10 seconds the relay clicks again. Inside on the main board there are I think 2 blinking green LED's, one solid green, and looks like 2 that are not lit. When the relay clicks for the second time, all of the LED's go out. Then after about 20 seconds, the cycle starts over where the TV is trying to come back up, and just repeats, off, on, off, on. It is not the power supply, I replaced it, same problem. I normally don't like to shotgun troubleshoot, but I've been looking around on the internet for many hours and have not found a solution. The power supply only cost me $64. I just ordered the main board (SSB) for $59. For me, time is money, but if anyone can help it would be much appreciated. Thanks from a newbie.
Reply from budm:
@electrodog, did you look real close at the two inverter boards to see if they have any damaged IC, fuses and MOSFET's on the Inverter boards since these boards are know to have blown IC and MOSFET's.
They will require modification if they are not done also.
Reply from me:
No, I have not gone that far removing the covers on the inverter boards, but can you tell me, will that cause the symptoms as I have described (no picture and no sound)? From what I have read so far, a bad inverter usually manisfests symptoms of no picture, but the audio is ok. Correct me if I am wrong, thanks.
Reply from budm:
If the inverter board shorted out, it will cause the 24V (for backlights) and 12v (for sound) power supply to shutdown, the 12V and 24V power supplies are generated by the same circuits. Best thing to do when you try to fix anything is to do visual inspection first. There is no 100% sure what have gone out since more than one circuit can also cause the same symptom.
Reply from me:
Yes, thankyou, I have done a visual inspection of the PS and main board looking for bad caps, burned components etc. As I mentioned, I haven't inspected the inverters, maybe while I'm waiting on my new main board, I'll check the inverter boards. Also, you provided me with an inverter modification II document. Should I assume this is something that needs to be done even if it is not the cause of my failure? What does the inverter mod fix? What is the failure mode that required this fix?
I'm not so sure if it is the inverters, but can I disconnect the power to the inverters to see if the unit will power up? Will this damage the PS? If I do this, should I use a load? I will not do this before I have visually inspected the inverters.
Sorry if this was very long. Thanks from a newbie.
Reply from budm:
@electrodog, did you look real close at the two inverter boards to see if they have any damaged IC, fuses and MOSFET's on the Inverter boards since these boards are know to have blown IC and MOSFET's.
They will require modification if they are not done also.
Reply from me:
No, I have not gone that far removing the covers on the inverter boards, but can you tell me, will that cause the symptoms as I have described (no picture and no sound)? From what I have read so far, a bad inverter usually manisfests symptoms of no picture, but the audio is ok. Correct me if I am wrong, thanks.
Reply from budm:
If the inverter board shorted out, it will cause the 24V (for backlights) and 12v (for sound) power supply to shutdown, the 12V and 24V power supplies are generated by the same circuits. Best thing to do when you try to fix anything is to do visual inspection first. There is no 100% sure what have gone out since more than one circuit can also cause the same symptom.
Reply from me:
Yes, thankyou, I have done a visual inspection of the PS and main board looking for bad caps, burned components etc. As I mentioned, I haven't inspected the inverters, maybe while I'm waiting on my new main board, I'll check the inverter boards. Also, you provided me with an inverter modification II document. Should I assume this is something that needs to be done even if it is not the cause of my failure? What does the inverter mod fix? What is the failure mode that required this fix?
I'm not so sure if it is the inverters, but can I disconnect the power to the inverters to see if the unit will power up? Will this damage the PS? If I do this, should I use a load? I will not do this before I have visually inspected the inverters.
Sorry if this was very long. Thanks from a newbie.
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