alba lcd19880h df whistling noise stuck in standby

[labrat]

hi ive got an alba 19" telly

it powers on but wont come out of standby and appears to have a whistling noise from the rear "hot" half of the power board.

i dont think its the caps as theyve been swap tested

any ideas?

[Turnip]

Hi Labrat,

Board numbers and / or pics would be handy - Chris.

[labrat]

hi sorry 

the power board thats whistling seems to be a combined power and invertor board number 17ips16-3

this image is taken from the web as its better photography from mine but is the same board



the whistling seems to be near those two large caps in the bottom left corner

[rebel-mc]

Normally it's the blue ceramic caps have went faulty.

[labrat]

this is going to sound really really stupid

how do  i tell what size caps to replace them with i cant seem to find many details on the actual caps themselves

theres a few strings of numbers down the side but on googleing them it doesnt really bring much up

[Turnip]

Hi labrat,

Whistling on the mains input area (as you suggest) could indicate secondary diode or other shorts - check diodes the secondary side of the chopper transformer - also check for whistle with output plug removed.  What are the secondary voltages  ?   - Chris.

[labrat]

hey turnip thanks for the advice

if you unplug it from the controller board (its one hardwire connection not ribbon) then the whistling stops and instead changes to a slow clicking noise

roughly same end of the board as the whistling...

[Turnip]

Hi Labrat,

Only thought is that with feed plug removed PS is in reduced output pulse mode (Maybe) Check 5v and 12v inputs on mainbord for shorts - what's the mainboard  ?

All the best - Chris

[labrat]

hi its a 17mb45-3

ill check for shorts if i get chance soon, when the dogs in bed and not likely to chew it

http://www.4shared.com/get/Q2iQXnnu/17MB45-3.html seemsto be the manual

[labrat]

wow long time since i updated this

the voltages on the board seem to be quite low, one pin wavers between 2.2 and 2.4v's etc

the 5v pin drops to 4.4 and the sound changes if you unplug standby light

im trying to look closer at the 5v line but im struggling tracing it back

i have another faulty tv arriving this weekend (not sure why people keep bringing me then), and the person who had this one has dropped off the radar i think it may have been forgotten

diodes going across seem fine theres 3 large ones center of the board, one reads about 5v the other two (close togeather) read 16v

[labrat]

ok readings for the caps

one side is 10v or 6.3v caps these all read around 4.5 - 4.9 so all ok on the 5v line

on the 16v side the first 4 read 15.8v and the last in line reads 0.2v so probably something iffy there

going to repalce that one now