TFT Screen blinking on and off when cold


At work we have about 150 CTX 17" TFT screens, model S760A. At about the time they were coming out of warranty we had a whole bunch of failures :-(

I contacted CTX but their reply was "I have spoken to my MD. She has said to order in the spare parts to repair these would be far too costly."

Upon investigation (Thanks to Allan Wheatley) it is the power board at fault. The S7 series power board rev A:10. There are 6 electrolytic capacitors on this board which are nicely located near a heat sink so get cooked.

C21 & C22 are 1000uF 16v (RS: 449-0980)
C15 & C16 are 1000uF 10v (RS: 315-0344 or 628-3784)
C17 & C20 are 470uF 16v (RS: 315-0467)

Make sure they are 105 degree C caps and not the cheaper low temp ones.

Total cost about £2! And that is only because RS supply in packs of 5.

photo of circuit board
close up photo of circuit board

Photos of the circuit board - capacitors highlighted in yellow. This is one I had just done so these are new capacitors.

Update (20/05/2009): It seems Acer model AL1711 has the same fault. Power board 715L1103-D (PWPC7425A3). Only 4 capacitors on this one.

C926 & C924 are 470uF 16v
C925 & C922 are 1000uF 16v

Update (27/10/2010): Another model - same problem. This time AMW X1900DS, Model MR19C-ABAD. Power supply board PI-SB02 Rev C. This has 4 capacitors as other models.
C829 is 1000uF 16v
C802 is 470uF 50v
C904 is 220uF 50v
C819 is 680uF 16v.
So far in the limited number I have seen - only C829 seems to be faulty.
Update (15/03/2011): Another one just in, same model - but completely lifeless. C829 was not present - C817 next to where C829 would normally be was looking a bit sick. C817 has same value as C829, 1000uF 16v.
Warning - this model of monitor is awkward to open - the silver bezel is levered away from the black body, starting with the bottom edge. Not for the feint hearted! And expect plastic marking.
Another update (10/03/2014) It seems the earlier models of this monitor have the power board PI-SB01 Rev 2.1. This has 6 capacitors to investigate on it.
C4P & C5P are 1000uF 25v 10% failure
C15P & C16P are 1000uF 16v 100% failure
C22P is 220uF 16v 25% failure
C37P is 220uF 25v 50% failure

Update (08/03/2011): Just had 2 Samsung 940B monitors in. Not blinking but failed back light. Holding a bright light to the front - display is there. Power supply board - 3 sick looking caps. C111, C112, C301 replaced (820uF 25v 105 degrees). Plus the fuse F301 (3A) had failed. Both now back working. When opening the case - ignore the plastic blanks on the back - just crack the screen edge open.

Update (11/10/2011): Just had a kind email from Paul Sarran saying thanks for putting these details online. He pointed me in the direction of 'The Cap King' who supply capacitor kits for monitors and PCs (with International shipping). They also link to LCDalternatives - who sell a large range of capacitor kits for monitors and TVs. Thanks Paul!