Fixing a DAC-19M005 Power Supply - check my DX:

[ned1]

Re: Fixing a DAC-19M005 Power Supply - check my DX:

So whats the part number for Q201 it says K7.2 on the part

[viziks]

Re: Fixing a DAC-19M005 Power Supply - check my DX:

Thanks ,I found the schematic and parts list as pointed out by you.

[alexanna]

Re: Fixing a DAC-19M005 Power Supply - check my DX:

Hello Guys I have a blown FET Q206 and resistor R210 burnt.
I understand from previous posts that R210 is 10ohms ,was wandering which transistors are Q201,203,204 and 209.
Also can "blackrider1" please post the schematics again as the Megaupload site has been taken down.

Thanks
Samir

Post 74 has the parts list for the transistors.And post 83 shows the schematic

[viziks]

Re: Fixing a DAC-19M005 Power Supply - check my DX:

Hello Guys I have a blown FET Q206 and resistor R210 burnt.
I understand from previous posts that R210 is 10ohms ,was wandering which transistors are Q201,203,204 and 209.
Also can "blackrider1" please post the schematics again as the Megaupload site has been taken down.

Thanks
Samir

[hucker55]

Re: Fixing a DAC-19M005 Power Supply - check my DX:

whare can ge a parts list

[PlainBill]

Re: Fixing a DAC-19M005 Power Supply - check my DX:

Yes I did measure these when they were in circuit, when I removed them from the board I used a pair of side cutters to cut the leads so there is no way I can measure now.
I wonder if this inverter circuit is similar to the royal oscillator we see in some of the Dells, and one half of it was staying on to long causing excessive amperage?
Maybe if PlainBill has some time he could give some idea what may have happened.
Here are the Digi-Key part numbers I used
MMBT4403-TPCT-ND
MMBT4401TPMSCT-ND
568-1369-1-ND

I'll have to look into it further, but at first glance it's not a Royer oscillator. At first guess, I'd suspect some sort of parasitic oscillations that weren't damped because the filter caps were bad.

PlainBill

[alexanna]

Re: Fixing a DAC-19M005 Power Supply - check my DX:

Good work! I suspect you tested Q201,03,04 and 08 while they were still in circuit? It would be interesting to see how they test out of circuit.

Yes I did measure these when they were in circuit, when I removed them from the board I used a pair of side cutters to cut the leads so there is no way I can measure now.
I wonder if this inverter circuit is similar to the royal oscillator we see in some of the Dells, and one half of it was staying on to long causing excessive amperage?
Maybe if PlainBill has some time he could give some idea what may have happened.
Here are the Digi-Key part numbers I used
MMBT4403-TPCT-ND
MMBT4401TPMSCT-ND
568-1369-1-ND

[blackrider1]

Re: Fixing a DAC-19M005 Power Supply - check my DX:

I´m glad to ear you fixed it too. I got different datas when testing the new ones out of the PCB and when they were soldered to it. That´s because I replaced components that seems to be ok. I had them, so, why not?
I´m sure that one ( or more) of the last I replaced was causing the problem. I kept them, so, I´ll try to test them and find out wich one is wrong.
Thanks again.

[jetadm123]

Re: Fixing a DAC-19M005 Power Supply - check my DX:

I have success to report also. I replaced Q201 Q203 Q204 and Q208,And this solved the problem.
None of these components Showed up as a short when they were tested.
I'm definitely not to try to analyze the inverter circuit, but I am wondering if one of the transistors or FETs was holding the circuit on to long causing a problem.
Thanks blackrider 1 for the schematic it did help me to find a problem area.

Good work! I suspect you tested Q201,03,04 and 08 while they were still in circuit? It would be interesting to see how they test out of circuit.

[alexanna]

Re: Fixing a DAC-19M005 Power Supply - check my DX:

Well, finally I got it working. According to the DAC-19M005 datasheet, I decided to follow the line from 16,5 V to the backlights transformer (from F200 ahead), and replaced Q204 (it was burnt, as you can see in the first picture),Q201,Q203 and Q208 ( Q203 and Q208 were okay but I replaced them too).
And Q200,Q202 ,ZD200 (weird meassures when testing),Q207 and D216 (They were okay too).
And finally, not necccesary but I did it, Q209 and Q210.
And now, it´s working.

PS: I replaced for the first time all caps (2 bulged and others),Q205 and Q206and ,although they were okay, F200,R210 and R206.
Thanks

I have success to report also. I replaced Q201 Q203 Q204 and Q208,And this solved the problem.
None of these components Showed up as a short when they were tested.
I'm definitely not to try to analyze the inverter circuit, but I am wondering if one of the transistors or FETs was holding the circuit on to long causing a problem.
Thanks blackrider 1 for the schematic it did help me to find a problem area.

[blackrider1]

Re: Fixing a DAC-19M005 Power Supply - check my DX:

Well, finally I got it working. According to the DAC-19M005 datasheet, I decided to follow the line from 16,5 V to the backlights transformer (from F200 ahead), and replaced Q204 (it was burnt, as you can see in the first picture),Q201,Q203 and Q208 ( Q203 and Q208 were okay but I replaced them too).
And Q200,Q202 ,ZD200 (weird meassures when testing),Q207 and D216 (They were okay too).
And finally, not necccesary but I did it, Q209 and Q210.
And now, it´s working.

PS: I replaced for the first time all caps (2 bulged and others),Q205 and Q206and ,although they were okay, F200,R210 and R206.
Thanks

[blackrider1]

Re: Fixing a DAC-19M005 Power Supply - check my DX:

Yes (#84):
"Recapped all the caps, changed Q206 and Q205, replaced F200 (although it was ok. I did it a continuity test. Why you guys do a GND-ONE TO OTHER SIDE test?) Replaced Q204 (it was burnt), Q208 (Not neccesary but I ordered them too), R210 and R206 (they were ok too)
All fuses seem to be ok (continuity test), I have 5V and 13,8 V at logic board connector (CN5).
All jumpers ( 0 SMD) are ok. "

That´s all I´ve changed.
Remember that my board hadn´t any blown fuse, just Q204 lokked like burnt.

[alexanna]

Re: Fixing a DAC-19M005 Power Supply - check my DX:

The very common failures of this board were capacitors, 2 Mosfets on the front of the board and the inverter fuse. Have you done anything with those?

[blackrider1]

Re: Fixing a DAC-19M005 Power Supply - check my DX:

An interesting thing:
To check what lamp flashes, I turned off the lights in the room, and now, i can´t see anything flashing. After checking if I moved something or not, I realized that is not a flashing backlight, : It is the change of luminosity of the panel, when off ( completly dark) and when on ( a little more gray) This change of tonality look like a small and short flash but you can see that just with light in the room, not in the dark.
So, no backlights at all. Sorry for this mistake.

[alexanna]

Re: Fixing a DAC-19M005 Power Supply - check my DX:

The power staying steady, With the back lamps flashing have me scratching my head!
Can you see if all the lamps are flashing or if it’s just one pair? It would probably best if you had some CCFLs that are not inside a panel

[blackrider1]

Re: Fixing a DAC-19M005 Power Supply - check my DX:

1,48V when green power led, with no pc connection and goes down to 0V when orange power led

[blackrider1]

Re: Fixing a DAC-19M005 Power Supply - check my DX:

Pin 6 --1,48V, a few seconds afters powering the monitor on.
According to the datasheet of the IC inverter, is ok, I think

[alexanna]

Re: Fixing a DAC-19M005 Power Supply - check my DX:

Pin 6 of the controller looks like it's the on/off pin, what is the voltage do you get on it?

[blackrider1]

Re: Fixing a DAC-19M005 Power Supply - check my DX:

At the logic board connector I get
5 V pin ---5 V
13.8 pin ---15 v

At pin 10 of the inverter controller ---- 4,8--4,9 V . It goes up and down ( maybe my pulse ) but not more than 4,9 v

Thanks

[alexanna]

Re: Fixing a DAC-19M005 Power Supply - check my DX:

From the way you describe your problem I am wondering if the backlight on signal is coming and going, to start, I would check it at the logic board connector, if that stays constant check and see what voltage is at pin 10 of the inverter controller