That voltage for U3 input is generated by that U6 AAT1164 chip above that inductor, you can down load the spec of that chip and start checking the voltages on those pin. http://www.alldatasheet.com/datashee...164C-Q5-T.html
ZD1 is pulsing 0-3.1v
ZD4 is pulsing 4.56-4.62v
R24 is pulsing 4.56-4.62v
Also rechecked the psu with no load 5v output is steady at 5.21v
but in picture of psu the jumper ringed in green shows 11.8v no load but when connected to the screen it fluctuates betwwen 12.01 and 12.33v .
Cannot borrow the supply i originally used to test as it appears it is not working so maybe my supply still has a fault so am going to change the
dm0565r green mode power transistor (one of the few bits not been replaced yet ) and then go from there
While your at is are Tvs1 & 2 surge protection resistors - they seem to go in bigger versions stopping sets from working but allow it to work when they are removed.
(dont really understand how that works)
The Tvs not sure what they are so just checked them on resistance and they all measure the same too .
Also reflowed the whole of the board just in case any bad joints .
I now have laid the whole thing out on my bench and connected it all together and have noticed that the inverter trans is buzzing in sync to the power going up and down ,whether that is because the power is fluctuating or thats whats causing it i am not sure.
Still seems odd there is nothing in that whole area. I'd test R166 as a fuse then with the power on see what voltage was on every test point in that part of the board.
Did you diode test the two zeners.
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Hi thanks for the pointers
U10 and U10 are both getting voltage in at a steady 3.2v and i cannot find any shorts .
Managed to find a sheet for the main logic ic controller and think this may be the problem as 3.3v are going in but the outputs fluctuate from 0 - 3.2v and should be at 3.3 steady
I have removed the large chip U7
Now the screen and power are no longer pulsing .
Not to say this is the problem but until new chip turns up in a couple of weeks and fitted (again ordered from Hong Kong as cant get here ) will have to see what happens from there .
So yet another job in the attic awaiting parts
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