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

[wenter]

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

Those are schotty diodes, google testing of those.
can you get pitcures of your boards?
Al.

I already posted pictures earlier, but here is another set

[alexanna]

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

Those are schotty diodes, google testing of those.
can you get pitcures of your boards?
Al.

[wenter]

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

What is the part number for these 2 transistors? A reading of 0.32ohms suggests that are shorted, but an in circuit test may not be 100% reliable because other components may be affecting this reading.

To be 100% sure, you will have to measure them out of circuit.

I pulled the transistors out and measured their resistance

Feet # 1 2 3 Feet # 1 2 3
1-2 116.6 1-2 92.2
1-3 0 1-3 0
2-3 0 2-3 0

In diod testing mode

1+ 2- 233 1+ 2- 174
1+ 3- 0 1+ 3- 0
3+ 1- 0 3+ 1- 0
3+ 2- 235 3+ 2- 174
2+ 1- 0 2+ 1- 0
2+ 3- 0 2+ 3- 0

Part # are visible on the attached picture but just to make sure
FCH10410 and SRF1060C

[retiredcaps]

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

I also tested resistance on two transistors in the top right corner connected to the L shaped heatsink.

Transistor #1 (on the left)
1-3 0.32
1-2 0
2-3 85.8

Transistor #2
1-3 0.32
1-2 0
2-3 112.1

What is the part number for these 2 transistors? A reading of 0.32ohms suggests that are shorted, but an in circuit test may not be 100% reliable because other components may be affecting this reading.

To be 100% sure, you will have to measure them out of circuit.

[alexanna]

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

I received my startup cap today. Soldered it in and....nothing. Clicking sound from the area of big capacitor and blinking power LED.

Monitor still does not work

Can you guys point me what and how I should check?

Thanks for the photo,Sorry my suggestion did not work for you.
Follow Plainbills and retiredcaps suggestions on diagnosing your problem as they are much better than that I am at this.
Something I am wondering about the clicking noise you are hearing, Can you identify where its coming from, It has been suggested to use a cardboard paper towel tube like one of those ste???ascope things {have no idea on spelling} to try to isolate it. Something very simple you could do would be to reflow solder on the thru hole stuff in that area. I have found in some cases solder joints that look good to the eye can still give a problem.

Al.

[PlainBill]

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

I've just looked through this thread. What we REALLY need are good quality pictures of the top and back sides of the power supply / inverter card. The fact that 5 volts are present at the logic card makes me wonder about the rest of the voltages.

PlainBill

[wenter]

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

Check for secondary voltages to the logic card.

Connect all your boards together including grounding screws.

Set your multimeter to read DC voltage 20V range. Black probe in COM, red probe in voltage.

Plug in your monitor. You do not have to power up, just have it plugged in.

1) on the logic card, put your black probe on a ground screw on the logic board. This is your ground.

2) Put your red probe on the connectors. Some should read 5V, some maybe 12V 19V DC depending on the design, and some are 0V (ground).

If you don't see any of these voltages, we will have to do different tests.

On 2 of them was 5v, on 3 or 4 was 4.94.
There was no 12v neither 19v.

I also tested resistance on two transistors in the top right corner connected to the L shaped heatsink. I numbered pins 1-2-3 when looking at the back of transistors from power connector.

Transistor #1 (on the left)
1-3 0.32
1-2 0
2-3 85.8

Transistor #2
1-3 0.32
1-2 0
2-3 112.1

[retiredcaps]

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

I received my startup cap today. Soldered it in and....nothing. Clicking sound from the area of big capacitor and blinking power LED.

Check for secondary voltages to the logic card.

Connect all your boards together including grounding screws.

Set your multimeter to read DC voltage 20V range. Black probe in COM, red probe in voltage.

Plug in your monitor. You do not have to power up, just have it plugged in.

1) on the logic card, put your black probe on a ground screw on the logic board. This is your ground.

2) Put your red probe on the connectors. Some should read 5V, some maybe 12V 19V DC depending on the design, and some are 0V (ground).

If you don't see any of these voltages, we will have to do different tests.

[wenter]

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

I received my startup cap today. Soldered it in and....nothing. Clicking sound from the area of big capacitor and blinking power LED.

Monitor still does not work

Can you guys point me what and how I should check?

[wenter]

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

Sorry, I meant which brand and make of capacitor did you order?

I ordered couple Panasonics from DigiKey.

[retiredcaps]

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

I believe the small one in the red circle is a startup cap.

Sorry, I meant which brand and make of capacitor did you order?

[wenter]

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

Which one?

Did you ever test for secondary voltages?

I believe the small one in the red circle is a startup cap.

No, I did not try the voltages yet, I'll wait for cap to come, solder it in and assemble the monitor together to check all things out.

[wenter]

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

wenter.
is there any you could post a good close up of the back of your board around the area of Q6thru q12.Something with the so-8 apm9435 mosfets dose not look right on my board. I just need to verify
Thanks Al.

Here is the best shots I can make with my camera

[retiredcaps]

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

I ordered new startup cap - will post when it'll be installed

Which one?

Did you ever test for secondary voltages?

[alexanna]

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

wenter.
is there any you could post a good close up of the back of your board around the area of Q6thru q12.Something with the so-8 apm9435 mosfets dose not look right on my board. I just need to verify
Thanks Al.

[wenter]

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

Thank you guys

I ordered new startup cap - will post when it'll be installed

[retiredcaps]

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

blinking pled clicking noise?

Just to expand, from what I have learned, the little cap is sometimes called a startup/run cap.

It helps the SMPS startup. The SMPS provides your secondary voltages (5V, 12V, etc). If the startup cap is bad, sometimes you will hear the SMPS start/restart (or click).

My questions about the secondary voltage and mains voltage and your findings may have eventually lead to this startup cap, but alexanna just took the shortcut to it!

[alexanna]

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

The one on my board is 22uf 50v
Al.

[wenter]

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

blinking pled clicking noise?
Try replacing the small cap.Thats next to the large cap.Use low E.S.R.
Also look real close at all solder joints.
Al.

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?

[alexanna]

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

blinking pled clicking noise?
Try replacing the small cap.Thats next to the large cap.Use low E.S.R.
Also look real close at all solder joints.
Al.