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**selldoor** · 01-16-2012, 01:57 PM

Re: Help fixing DAC-19M005 BF REV 01A

Why have you started a new thread?
You will need to post clear pictures of both sides of your boards.

**chico1st** · 01-17-2012, 08:06 AM

Re: Help fixing DAC-19M005 BF REV 01A

I posted this because so far I haven't found any threads which helped me, at the moment I am mostly curious if those voltage levels are acceptable, and if that noise means anything to anyone (the 1 second repetition makes it seem special to me).

I know electronics fairly well as a note.
And i forgot to mention i used Panasonic FC/FM for replacements
and i retract what I said about measuring 170VDC after the diode bridge, that makes perfect sense.

Pictures attached

Attached Files

**selldoor** · 01-17-2012, 10:10 AM

Re: Help fixing DAC-19M005 BF REV 01A

Hi - Good Pictures- I know very little about electronics - still learning.
Can you confirm which fuse is blowing - there are three.
With the power off can you test and report the resistances on the
inverter transformer (across the end pins) http://www.lcdparts.net/Images/Transformer/Seconary.jpg.

Also test and report the voltages on pins of CN5

**chico1st** · 01-17-2012, 11:54 AM

Re: Help fixing DAC-19M005 BF REV 01A

Awesome, Im just starting to learn about fixing electronics

Yup, there are 3 surface mount fuses and 1 through hole (F102), only F200 is blowing though which seems to power most of the 2nd 1/2 of the circuit.

For the secondary transformer, I measure 0.7Kohm across the end pins (1-8 and 4-5) like you asked me to measure, this seems very high.
And just for fun i measured across the transformer, its open between the two ends (1-4 and 5-8).
2-7 and 3-6 are very low ~0.2ohm or something

On the connector, I had a lot of 0 readings but I didnt have the mating board connected, just the inverter to the AC plug.
1-0V jumpy (1-2 was 0V steady)
2-0V jumpy
3-0V jumpy (3-4 was 0V steady)
4-0V jumpy
5- 0V jumpy
6- 0V jumpy
7-0V jumpy
8-15.1V steady
9-5V steady
10-5V steady
11-0V steady
12-0V steady
13-0V steady
14-0V steady
15-0V jumpy
16-0V jumpy

**selldoor** · 01-17-2012, 02:06 PM

Re: Help fixing DAC-19M005 BF REV 01A

Hi "0.7Kohm across the end pins (1-8 and 4-5)" that is good -both readings should be within 3%

I have been re-reading some of the threads and it keeps cropping up that the bad caps put pressure on the mosfets which short and take out the fuse. Perhaps you could re test the mosfets. It may be better to test out of circuit - there are videos on Utube and this link for a written test http://www.4qdtec.com/mostest.html

This an IN Circuit test posted by "Retiredcaps"
Mosfets
---------

If you have a manual range multimeter, set it to 200 ohms (two hundred). You can test a mosfet (Q, IC designation) "in circuit" by (power off and unplugged)

a) black on pin 1- red on pin 2 - record ohms
b) black on pin 1- red on pin 3 - record ohms
c) black on pin 2- red on pin 3 - record ohms

If any ohm reading is less than 30 ohm you might have shorted mosfet. Remove from circuit and repeat the tests to verify.

**retiredcaps** · 01-17-2012, 06:17 PM

Re: Help fixing DAC-19M005 BF REV 01A

See all the little SMD Q transistors on the backside as posts #94 to #99

https://www.badcaps.net/forum/showth...ight=4a&page=5

**jetadm123** · 01-17-2012, 07:47 PM

Re: Help fixing DAC-19M005 BF REV 01A

Originally posted by chico1st View Post

Hi there I have spent some time trying to fix my DAC-19M005 BF REV 01A in my AL1916W monitor.

My fuse blew and then reblew when I dropped in a 2A replacement.

On a different post you reported that the original fuse was marked "M" or "W" and someone responded that it was a 4A fuse. Why are you using 2A?

**retiredcaps** · 01-17-2012, 07:53 PM

Re: Help fixing DAC-19M005 BF REV 01A

Originally posted by jetadm123 View Post

On a different post you reported that the original fuse was marked "M" or "W" and someone responded that it was a 4A fuse. Why are you using 2A?

Which is exactly why we hate cross posting in different threads as per post#2.

**chico1st** · 01-17-2012, 09:50 PM

Re: Help fixing DAC-19M005 BF REV 01A

The person (selldoor) who responded said that the 2Amp should work and I ought to fix whatever is causing it to blow.

A 2Amp fuse will give your circuits better protection but may blow more often.

Ideally you need to know first what caused it to blow and if you dont youd better buy a few.

this made sense to me to try to find the cause but would you guys recommend to just try the 4A fuse?

You hate cross posting, ok I can stop, based on the fact that the 2A fuse should work I didn't know what was the cause of my failures.
Most other forums i wander around in want people to separate threads whenever possible to not create super long threads, but point taken I should keep them all under one thread.

I have 4 of these monitors to fix, should they all go in one thread? if i have issues on one of the others?

**retiredcaps** · 01-18-2012, 01:51 AM

Re: Help fixing DAC-19M005 BF REV 01A

Originally posted by chico1st View Post

this made sense to me to try to find the cause but would you guys recommend to just try the 4A fuse?

Most boards have a warning that says something like "Replace fuse with EXACT values". I don't go up or down when I replace a fuse. I replace it with the exact value.

You hate cross posting, ok I can stop, based on the fact that the 2A fuse should work I didn't know what was the cause of my failures.

There are maybe 5 or 6 regulars on this subforum and I'm one of them. I may be participating in 20 to 30 threads in one day. I don't get paid to do this so anything that makes my life harder, I'm just going to skip over the thread and move on.

Most other forums i wander around in want people to separate threads whenever possible to not create super long threads, but point taken I should keep them all under one thread.

We have had people in the past blast every subforum with the same question. Some regulars here have their own area of interest and never see the responses that are cross posted.

What is acceptable in one forum may not be the same in another forum. Each has its own "culture".

I have 4 of these monitors to fix, should they all go in one thread? if i have issues on one of the others?

If they are all the exact same monitor, then yes, keep it in one thread. For your sake and ours, work on one at a time and ask questions for one at a time. Asking us to keep track of 4 monitors that may or may not have the same problem is impossible when I'm participating in 20 to 30 threads daily.

Obviously, it is a free world and you are welcome to do whatever you want and I may not have anything to contribute. Just remember I took time to research your problem and make a suggestion in post #7 that very well could be the solution?

**chico1st** · 01-18-2012, 10:00 AM

Re: Help fixing DAC-19M005 BF REV 01A

Is there some point that I can probe to know if the backlight should work?
Possibly one of the voltages on CN200-CN203

**PlainBill** · 01-18-2012, 01:21 PM

Re: Help fixing DAC-19M005 BF REV 01A

Originally posted by chico1st View Post

Is there some point that I can probe to know if the backlight should work?
Possibly one of the voltages on CN200-CN203

In the top view of the power supply/ inverter the two top pins of that connector control the inverter. The legend is obscured in the picture. It is also possible to measure the voltages on certain pins of U200 - the inverter controller.

PlainBill

**selldoor** · 01-18-2012, 02:36 PM

Re: Help fixing DAC-19M005 BF REV 01A

Originally posted by chico1st View Post

Is there some point that I can probe to know if the backlight should work?
Possibly one of the voltages on CN200-CN203

Probe CN200 to CN203
I would say NO!!! - I doubt if your meter can stand it
Please read up on Inverter transformers output voltage and or CCFL Voltages and you will see what I mean. The 4 Warnings in this area of the board should give you a clue.

If you can get the correct voltage going into the Inverter Transformer and we have established that that appears to be ok then the voltages coming out should be ok.
Whether the CCFLS are ok is a different question- there are many examples of how to test a ccfl - (I use an old laptop others use another monitor where it is known the power supply is good or you can buy a ccfl tester.

You dont seem to want to follow the advice given on the forum?
Did you try a 4 Amp fuse?
Did you re test the Mosfets - there is some discolouration where Q206 goes through the board.?
Did you do the tests that retired caps suggested? Post7 i think

**chico1st** · 01-18-2012, 09:17 PM

Re: Help fixing DAC-19M005 BF REV 01A

ah i am following the advice, the 4A fuse is coming tomorrow from digikey and i plan to do the suggested mosfet test tomorrow before put I put the fuse in.

I just wanted to know what I could probe once the fuse is back in. I thought it would be a simple test to check if it was working before i plugged it to the ccfl.

**chico1st** · 01-19-2012, 01:11 PM

Re: Help fixing DAC-19M005 BF REV 01A

No luck.

I tested the mosfets in and out of circuit and they were fine, i followed the posted method, but just so everyone knows when doing these tests it is easy to charge the FET and thus read a shorted output between drain and source, until you discharge it by shorting drain and source. (like in this test)

I plunked the 4A fuse (F1459CT-ND) in and it blew when I turned on the monitor.

I suppose Ill look into those Q-Transistors next.

See all the little SMD Q transistors on the backside as posts #94 to #99
https://www.badcaps.net/forum/showthr...ight=4a&page=5

Is my 15.1V reading instead of 16.5V reading OK or is that a sign of something?

**retiredcaps** · 01-19-2012, 01:22 PM

Re: Help fixing DAC-19M005 BF REV 01A

Originally posted by chico1st View Post

Is my 15.1V reading instead of 16.5V reading OK or is that a sign of something?

In post #13, PlainBill made a subtle hint regarding the legend being obscured in the photo.

I always go by what is marked on the board.

On some impmentations of power supplies, the secondary voltages are not regulated. Once a stable load is applied, then the voltage follows what is marked on the legend.

**PlainBill** · 01-19-2012, 08:25 PM

Re: Help fixing DAC-19M005 BF REV 01A

Originally posted by chico1st View Post

No luck.

I tested the mosfets in and out of circuit and they were fine, i followed the posted method, but just so everyone knows when doing these tests it is easy to charge the FET and thus read a shorted output between drain and source, until you discharge it by shorting drain and source. (like in this test)

I plunked the 4A fuse (F1459CT-ND) in and it blew when I turned on the monitor.

I suppose Ill look into those Q-Transistors next.

Is my 15.1V reading instead of 16.5V reading OK or is that a sign of something?

One thing I do to save on fuses until the problem is found is to use a current limiter. My favorite is a 1157 automotive lamp. Using that as a temporary replacement for the fuse allows easier troubleshooting. If the lamp glows at full brightness, the problem is still present. If it glows brightly for an instant, then gets dimmer, the problem has been solved.

PlainBill

**chico1st** · 01-21-2012, 02:03 PM

Re: Help fixing DAC-19M005 BF REV 01A

OK so I dont know if I'm making progress or not but now my backlight flashes along with my green LED indicator on the power switch. Probably about once a second and turns off, it makes a ticking sound just like before, but when the backlight is plugged in the noise is much louder.

All of the other SMD transistors measured well so I think I will go looking for the cause of that noise, I know the poster of that problem said they measured well but ill look for this odd ticking noise first. I have a high speed scope I can use to try to find some voltage spike but I expect any spike to permeate most of the circuit.

After you mentioned that I should hook up a lightbulb across the fuse I realized I should just use my ammeter there

... totally forgot I had that.

2 questions:
can I run the board without having the CCFLs plugged in?
If the CCFLs were blown (shorted lets say) would the circuit power down and then retry to start up? that would explain this flashing.

**alexanna** · 01-22-2012, 08:18 AM

Re: Help fixing DAC-19M005 BF REV 01A

Originally posted by chico1st View Post

OK so I dont know if I'm making progress or not but now my backlight flashes along with my green LED indicator on the power switch. Probably about once a second and turns off, it makes a ticking sound just like before, but when the backlight is plugged in the noise is much louder.

All of the other SMD transistors measured well so I think I will go looking for the cause of that noise, I know the poster of that problem said they measured well but ill look for this odd ticking noise first. I have a high speed scope I can use to try to find some voltage spike but I expect any spike to permeate most of the circuit.

After you mentioned that I should hook up a lightbulb across the fuse I realized I should just use my ammeter there

... totally forgot I had that.

2 questions:
can I run the board without having the CCFLs plugged in?
If the CCFLs were blown (shorted lets say) would the circuit power down and then retry to start up? that would explain this flashing.

I think if you had that serious of a problem with a CCFL you would hear something other than a ticking noise.
I think this particular power supply is monitoring the 16volt rail, when you have the ammeter installed in place of F200 the SMPS realizes something is drawing excessive current and shuts down to try to prevent damage.
What you are experiencing sounds almost exactly a problem I was experiencing with a DAC-19m005 that I was working on. Have you read the thread that retiredcaps posted a link to?
Look at the schematic below it will show you the circuit.Even though you have tested these components for being shorted; they are still highly suspect for causing your problem.*I THINK* if you were to hook a scope up to check the signals you would find one that was not switching properly or holding on to long.
The Q transistors and mosfets are readily available, and are not that expensive; from what I have experienced on this board I would replace them.

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