DWW750FM short circuit?

bling23 · 03-20-2008, 11:37 PM

hey guys,

i hope someone here can help me out.
i was installing my DWW750FM today and i accidentally touched the live wire on the metal casing and im not too sure if i blew something but what used to display letters on the main screen didn't display anymore.
the power looks on as the blue lights still lights up but other than that
i don't see anything else.
anyone has any esimilar experience or knows what to do?

morris_the_cat · 03-21-2008, 08:53 AM

have you checked the fuse?

bling23 · 03-21-2008, 01:03 PM

yup.
the power fuse is intact
i can't find any other fuse.

bling23 · 03-24-2008, 12:34 AM

no one can help?
pls sopmeone help!

bbalazs · 03-24-2008, 04:23 AM

Ok, but we have to know about your experience to fit the level of explanations.
eg. do you have a multimeter? Is the backlight on so it shows white screen or there is a dark display? Can you take a photo about the main PCB?

Are you absolutely sure, the main cause od the accident was that?
If you accidentally touched the live (you mean +12V? or what else?) to the metal there were any sparks and sounds of sparking visible/audible?

Just a quick advice: check ALL the ribbon cables.

bling23 · 03-28-2008, 03:35 AM

i have a multimeter.
theres no visible damage to the board whatsoever after i took it out.
theres no fuse and i can't see anything unless i have the circuit diagram.

the blue lights are on.
and i believe the backlights are on but usually the backlight will be on with the white wordings but now theres no white wordings.

yes, absolutely sure. there was some sound and my cigarette lighter fuse broke.
cos i was using the power from the cigarette lighter.

i used the multimeter to check the power fuse(of the radio) but its still working.
can't seem to find any other fuses to check.
i didn't touch the ribbon cable.
and theres only one main one to the screen? right?

bbalazs · 03-28-2008, 08:10 AM

It is easy to check the backlight. Turn it on in pitch black. Cover the blue led with your thumb finger. Can you see any light from the display? Do not care about that text, it is not visible unless the backlight is on. On the pcb of the backlight there is usually another fuse (sometimes looks like an ordinary resistor, but marked as F1 or F(x).
If you can not see any light and the F(x) seems to be intact, check those FETs near to the high voltage transformer. Check the secondary part of the transformer.

Another possibility in the case of no backlight
Get a light tube driver (case modding element) and attach it to your tube. Turn it on, switch on your lcd. If there is anything on the screen, the backlight was unfunctional.

morris_the_cat · 03-28-2008, 03:29 PM

Hey, while you have it apart, do you see any sort of a reset button inside? My radio is frozen & probably just needs to be reset.

Hope you figure out how to fix yours....

bling23 · 03-28-2008, 11:09 PM

this is the headunit PCB

and the back of it.
i believe this is the amp PCB

this is the PCB foudn at the back
i believe it is the radio PCB

this is the main PCB

as you can see i took extra picture of the transformer.

this is the close up picture near the transformer where i saw some brown color stuff which i may believe that is the burnt area.
other than that, i cant find the F(X) or something similar that you are talking about.

maybe you can tell me which picture and which part you are referring to.

thank you for your help.

bbalazs · 03-29-2008, 05:01 AM

OK, but you did not answer, whether there is ANY symptom of working backlight...
Check it regarding my method in previous post.
That is VERY important, because without backlight we can not see anything (perhaps the lcd is working, but not visible). Until it is not serviced or at least substituted, you are not capable to say anything about the functionality of other parts.

Do you think, that is a real burning? It seems to me as a simple glue-like material eg. resin from the soldering tin or result of a special fluidizer.
If not, check those elements and parts near to the 'burning'.

The switching FETs are above the transformer on both side of that smaller coil on the picture before last. I think all the pins of that 8-legged chip on one side are connected, and three pins on another side are also, but one pin in the corner is the gate.
Switch your multimeter into diode-checker, and investigate as a diode in both direction between to opposite pins on the left side of the switch, concerning the title of the chip is NOT upside down.

That F(x) is, where x represents a number, without parenthes, eg. F1, F2, F3, etc...

bling23 · 03-29-2008, 05:36 AM

i tried to do that.
i can't really tell you specifically if there is backlight.
but im more inclined to believe that the backlight is faulty.

when the power is on and the blue LED covered in a dark room, i see very slight lighting up of the small main screen of those small default images. but it is really slight so i don't think its considered the backlight.

i cabnt seem to find any F stuff. which picture can i find the F?