Samsung le40r81b no backlight
Good day folks. Got this Samsung telly here which has no backlight and I'm pretty sure the CCFLs are to blame, but I thought I'd ask for another opinion, as there are a couple of other things that seem "off". It's an unusual setup which I haven't encountered before: the inverter is powered straight off the main cap CP809 at 380v and despite having an HV transformer on the PSU itself, there's also a separate inverter board with smaller transformers (what you usually expect to see in a TV like this), so how does this work ? HV is turned into even higher HV ? The control IC ICI801 is on the PSU, not the inverter. I've attached the schematic for the PSU.
The main cap is slightly bulged and it just so happens it also feeds the inverter, so that could be one of the reasons. Another oddity is that I can't measure this cap: when the PSU is in standby ("ON" pin NOT strapped to 5v), I get around 300v on it (which is slightly low for my taste). When I turn the PSU on, the meter goes apesh!it and can't "lock" onto a reading...it seems to me the ripple becomes so high on that cap that it's like trying to measure a high frequency AC, which usually results in this erratic behavior of a regular run of the mill meter like this one...too bad I don't have a scope. There was a blown cap on the 12v rail which I replaced just for good measure, though I was sure it has nothing to do with the issue at hand. ICI801 does receive VCC, so I can assume it operates properly. After a bit of digging, I even tried tying one of its pins (I think 14) to GND in an attempt to fool it into turning on, but it didn't work, hence why I believe the problem may not be strictly inverter-related.
At the end of the day it could very well still be the classic CCFL lamp failure, but it doesn't even come on for like a second...not even a flash, I though there'd be at least a flash of backlight or something, but no - nothing at all. TV works fine otherwise, I forgot to mention.
Any thoughts ? I'll replace that cap no doubt, obviously, but what about the rest ? Anything else I should look out for ? Picture of the bottom is pretty piss-poor, but I can take a better one if so desired.
The main cap is slightly bulged and it just so happens it also feeds the inverter, so that could be one of the reasons. Another oddity is that I can't measure this cap: when the PSU is in standby ("ON" pin NOT strapped to 5v), I get around 300v on it (which is slightly low for my taste). When I turn the PSU on, the meter goes apesh!it and can't "lock" onto a reading...it seems to me the ripple becomes so high on that cap that it's like trying to measure a high frequency AC, which usually results in this erratic behavior of a regular run of the mill meter like this one...too bad I don't have a scope. There was a blown cap on the 12v rail which I replaced just for good measure, though I was sure it has nothing to do with the issue at hand. ICI801 does receive VCC, so I can assume it operates properly. After a bit of digging, I even tried tying one of its pins (I think 14) to GND in an attempt to fool it into turning on, but it didn't work, hence why I believe the problem may not be strictly inverter-related.
At the end of the day it could very well still be the classic CCFL lamp failure, but it doesn't even come on for like a second...not even a flash, I though there'd be at least a flash of backlight or something, but no - nothing at all. TV works fine otherwise, I forgot to mention.
Any thoughts ? I'll replace that cap no doubt, obviously, but what about the rest ? Anything else I should look out for ? Picture of the bottom is pretty piss-poor, but I can take a better one if so desired.
Attached Files
As I removed it and shook it around, I could hear like a rubber ball bouncing around inside of it, so all of its insides must've dried out and shrunk...case closed.
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