Need help DCLCD 19" LCD Monitor - I already replaced caps

[DJM_PHX]

Re: Need help DCLCD 19" LCD Monitor - I already replaced caps

I am not even gettiing 1V out of any of the wires on the long connector as listed before, even with the new cap.

[DJM_PHX]

Re: Need help DCLCD 19" LCD Monitor - I already replaced caps

Ok, the 22uF cap is in and no change. The clicking noise is still there. Replace the 100uF large cap next I assume?

[retiredcaps]

Re: Need help DCLCD 19" LCD Monitor - I already replaced caps

I guess I will have to wait until the new cap arrives.

Where and what brand/series did you order? If USA digikey, most here say it arrives in 2 days or less.

[DJM_PHX]

Re: Need help DCLCD 19" LCD Monitor - I already replaced caps

Ok thanks. I guess I will have to wait until the new cap arrives.

[retiredcaps]

Re: Need help DCLCD 19" LCD Monitor - I already replaced caps

I can hear a steady ticking noise that coincides with the voltage pulses mentioned earlier.

The ticking is the SMPS controller trying to start up. If the little cap is proven to be bad and replaced with a good one, the ticking will go away.

[DJM_PHX]

Re: Need help DCLCD 19" LCD Monitor - I already replaced caps

I put the cap back in. No difference. I can hear a steady ticking noise that coincides with the voltage pulses mentioned earlier. I seems to be in the area of the yellow transformer or the sink next to it. I can't pinpoint it. Any input on this?

[DJM_PHX]

Re: Need help DCLCD 19" LCD Monitor - I already replaced caps

Right now I have the 22uF cap out so I can't try it. I may just put it back in and give it a try since the new caps haven't arrived yet.

[jetadm123]

Re: Need help DCLCD 19" LCD Monitor - I already replaced caps

I am waiting for my 22uF caps to come in so in the mean while, I was reflowing the solder on the connector and the transformers as you suggested to others.

On the SOIC-8 PWM chip, I found a single strand of copper wire that looked like it was laying between the two pins where the yellow line off the yellow circle is on the attached pic. I had it under a microscope and when so I brushed it off of the board. It was so small, I couldn't find it on the table. Maybe a failure mode?

I also measured the 22uF cap with a Fluke and it returned 21.7uF. Hmmm... I don't know about under a load though.

If that wire was across pins 4 and 5, then it could have shorted the output of the chip to ground. With the wire removed, does the monitor shows any different signs of life?

[DJM_PHX]

Re: Need help DCLCD 19" LCD Monitor - I already replaced caps

I just saw that our HP4284A's can measure ESR. Now I just need to find some leads to use.

[DJM_PHX]

Re: Need help DCLCD 19" LCD Monitor - I already replaced caps

Thanks. I was suprised that ours read uF's. I know we do not have one that returns ESR.

[retiredcaps]

Re: Need help DCLCD 19" LCD Monitor - I already replaced caps

I also measured the 22uF cap with a Fluke and it returned 21.7uF.

uF may be correct, but ESR (ohms) may be too high. I don't know of any Fluke that will measure ESR.

[DJM_PHX]

Re: Need help DCLCD 19" LCD Monitor - I already replaced caps

SG3842GS
ADAX87140421E

I am waiting for my 22uF caps to come in so in the mean while, I was reflowing the solder on the connector and the transformers as you suggested to others.

On the SOIC-8 PWM chip, I found a single strand of copper wire that looked like it was laying between the two pins where the yellow line off the yellow circle is on the attached pic. I had it under a microscope and when so I brushed it off of the board. It was so small, I couldn't find it on the table. Maybe a failure mode?

I also measured the 22uF cap with a Fluke and it returned 21.7uF. Hmmm... I don't know about under a load though.

[SMITHWHO]

Re: Need help DCLCD 19" LCD Monitor - I already replaced caps

i checked all solder joints - they seems to be fine. I can not read if the little cap is 22uf 50v or it is 2.2uf 50v.

Does anybody know what it is?

its 22 mf 50 volts on my dclcd

[SMITHWHO]

Re: Need help DCLCD 19" LCD Monitor - I already replaced caps

Needs del

[DJM_PHX]

Re: Need help DCLCD 19" LCD Monitor - I already replaced caps

Yes,Look at post #33 and #34
Al.

Thanks, missed that scanning thru.

[alexanna]

Re: Need help DCLCD 19" LCD Monitor - I already replaced caps

Does 22uF 50V sound correct for the small cap? They had so much of the white goop on it that the printing mostly came off trying to clean it.

Yes,Look at post #33 and #34
Al.

[DJM_PHX]

Re: Need help DCLCD 19" LCD Monitor - I already replaced caps

Does 22uF 50V sound correct for the small cap? They had so much of the white goop on it that the printing mostly came off trying to clean it.

[retiredcaps]

Re: Need help DCLCD 19" LCD Monitor - I already replaced caps

if after many on and off trys it will come on and stay on

Sounds very much like caps that exhibit high ESR. As the lcd warms up, the cap's ESR drops enabling the lcd to turn on.

Also, please find the "." on your keyboard. It makes your posts more understandable.

[jetadm123]

Re: Need help DCLCD 19" LCD Monitor - I already replaced caps

[QUOTE=SMITHWHO;142248]

dclcd 19" monitor turn monitor on boot up window log comes on. then goes black if i turn the monitor off then
on the screen comes on for second or two then black
if i turn the monitor off and then on screen comes on for
a second or two
if after many on and off trys it will come on and stay on
it will continue as long as you use it even with screen saver. but if you let it sleep then we are back at turn off and on I did find the large cap 100md 400 volt to be bad
I CHECKED EVERY THING SUGGEST BY YOU HELP PLEASE
sincerly j.r. Smith

my

That's unusual, since the large cap very seldom fails. It's usually the small caps that fail. What you're describing is a very good example of a problem caused by bad caps. While the caps you measured capacitance wise may have checked ok, they could still have a high ESR, which could cause the problems you're seeing. There is one small cap mentioned on the previous posts of this thread that if failing, can cause startup problems.

[SMITHWHO]

Re: Need help DCLCD 19" LCD Monitor - I already replaced caps

[QUOTE=SMITHWHO;141121]

dclcd 19" monitor turn monitor on boot up window log comes on. then goes black if i turn the monitor off then
on the screen comes on for second or two then black
if i turn the monitor off and then on screen comes on for
a second or two
if after many on and off trys it will come on and stay on
it will continue as long as you use it even with screen saver. but if you let it sleep then we are back at turn off and on I did find the large cap 100md 400 volt to be bad
I CHECKED EVERY THING SUGGEST BY YOU HELP PLEASE
sincerly j.r. Smith

my