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

[alexanna]

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

Yes I have a 005 board it has been scavenged of some parts ,But there should be enough left to trace the 5V and 12v circuits.
Look closely at the schotty diodes D103 and D102,One is a SBT100 and I am not sure of the other, but it will be similar. Search the data sheet as for as testing goes, you most likely will find these shorted.
Al.

[kingofcoins]

Re: Fixing a DAC-19M005 Power Supply - tracing down a short

Two things..
Ok, both my F101 and F200 have a zero reading to ground on one side, so I assume I have to start with the F101 since it also shows infinity across itself ?
Also do you have a component/wiring layout for a typical or similiar power supply board ?
well, Three...Happy New Year !

[alexanna]

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

yes on the power supply.
You're going to try to analyze the circuit ,trace it back from the fuse see if you can see a component that shows low resistance similar to the fuse .If you find one remove it from the circuit and retest the fuse to see if it's still shorted .I don't think we will find a wiring diagram.
Al

[kingofcoins]

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

You mean on the power supply board to find a sort ? Can you give me a primer on doing this tracking ? I haven't been able to track down a schematic for this model. Have you anything ?

[alexanna]

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

If You have problems tracing the circut to find the short,I'll try to look at my board sometime tomorrow.
Al

[alexanna]

Re: Fixing a DAC-19M005 Power Supply - fuses

Al... with the power supply board disconnected and power off I get infinity to ground on one side of F100, and 14 ohms on other side to ground.
And on F101 infinity to ground on one side, and 0+/- ohms on other side.
That F200 fuse btw reads 0 to ground one side, and 6 ohms to ground on other.
Any need now to join the logic board for this measurement?

No you don't have to hook anything else up.
Let the fun begin, You're going to have to trace the circuit.
Al.

[kingofcoins]

Re: Fixing a DAC-19M005 Power Supply - fuses

Al... with the power supply board disconnected and power off I get infinity to ground on one side of F100, and 14 ohms on other side to ground.
And on F101 infinity to ground on one side, and 0+/- ohms on other side.
That F200 fuse btw reads 0 to ground one side, and 6 ohms to ground on other.
Any need now to join the logic board for this measurement?

[alexanna]

Re: Fixing a DAC-19M005 Power Supply - more fuses

Good pics, good eyes, good minds and good guys..that's why I like this place...
Happy New Years Guys !
You too Al !

Al....> If you look back to my thread opening pic at post #10, it shows that CE 109 as the 'big' mistake I made when I first tried re-capping. This now is months later and my pic at post #27 shows the correctly installed new cap.
I didn't know this board had so many fuses...yes both F100 and F 101 are open.
Do you think these blew from my ccfl lamp trials? Or part of the original damage?
What else needs check prior to trying new fuses ?

I would bet during your testing something shifted and a power came into contact with a ground.
With everything powered off and for right now disconnect the logic board, check with your ohmmeter on both side of those fuses for a very low ohm reading to ground. If you're not finding any shorts try again with the logic board connected.
Al

[kingofcoins]

Re: Fixing a DAC-19M005 Power Supply - more fuses

Good pics, good eyes, good minds and good guys..that's why I like this place...
Happy New Years Guys !
You too Al !

Al....> If you look back to my thread opening pic at post #10, it shows that CE 109 as the 'big' mistake I made when I first tried re-capping. This now is months later and my pic at post #27 shows the correctly installed new cap.
I didn't know this board had so many fuses...yes both F100 and F 101 are open.
Do you think these blew from my ccfl lamp trials? Or part of the original damage?
What else needs check prior to trying new fuses ?

[alexanna]

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

I lost the 12V and 5v to the logic board, there seems to be fluctuating voltage to the inverter at the mosfets. I rechecked my soldering both with a 10x loupe, and by running continuity. The caps all seem to have an appropriate ESR. Bridge rectifier still has same readout as pre-repair.
The last time in I replaced those mosfets,...are they suspect again ? Whats best way to check them in circuit with a VOM ?

I was looking at the top view of the power supply.
Is CE109 installed correctly?
Al.

[alexanna]

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

Have you checked fuses F100 and F101 they are on the back of the power supply near the connector to the logic board?
Al.

[kingofcoins]

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

I lost the 12V and 5v to the logic board, there seems to be fluctuating voltage to the inverter at the mosfets. I rechecked my soldering both with a 10x loupe, and by running continuity. The caps all seem to have an appropriate ESR. Bridge rectifier still has same readout as pre-repair.
The last time in I replaced those mosfets,...are they suspect again ? Whats best way to check them in circuit with a VOM ?

[alexanna]

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

Thanks all 3 of you for checking in...I having a time with this one......or its just this time of year the supply has died...

Yes Rtech... I replaced all those components you speak of except my F200 has never blown

Retired/Al... I was unplugging one lamp at a time and leaving 3 on...but as you suggest I followed up using a test lamp plugging it in one spot at a time....first lamp no change, BUT when I tried in place of the second lamp the 12v power was lost...no noise, no smell, no signs,....SO I'm back to square one no lights, 161V at main, all fuses check OK, but no secondary DC voltage. Please list the items I should now recheck so I don't miss any...oh and my digital had to go back to the rat-shack so only have a VOM to use now.

Did you lose your 5V and 12v to the logic board or to the 12v to the inverter?
Re check all your soldering wiggle the capacitors look for movement on the solder pads.
Al.

[kingofcoins]

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

Thanks all 3 of you for checking in...I having a time with this one......or its just this time of year the supply has died...

Yes Rtech... I replaced all those components you speak of except my F200 has never blown

Retired/Al... I was unplugging one lamp at a time and leaving 3 on...but as you suggest I followed up using a test lamp plugging it in one spot at a time....first lamp no change, BUT when I tried in place of the second lamp the 12v power was lost...no noise, no smell, no signs,....SO I'm back to square one no lights, 161V at main, all fuses check OK, but no secondary DC voltage. Please list the items I should now recheck so I don't miss any...oh and my digital had to go back to the rat-shack so only have a VOM to use now.

[alexanna]

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

The normal faults on these,as they are also use in Viewsonic VA1912-4,can usually be solved by changing the following.
C204 and Ce101,also Q205 and Q206,and the fuse on the underside between C204 and Ce101.If you have done these,then it would seem to indicate a faulty CCFL,as suggested,or, I presume you have checked the resistance of the output transformer feeding the ccfl skts,and both secondaries are equal + or - 5% ??

Definitely check the ccfls and the inverter transformers as retiredcaps and Rtech, suggested.
Check out post # 299 of this thread. https://www.badcaps.net/forum/showth...1975nw&page=15
I wouldn’t think you f200 would be faulty because you’re seeing a flash of the back lamps, but transistors can fail in other ways besides a short.
the area I have circled is the area that I think Kahless was talking about.
Personally I don’t have any experience of these failing, It’s just something I have read
Al.

[Rtech]

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

The normal faults on these,as they are also use in Viewsonic VA1912-4,can usually be solved by changing the following.
C204 and Ce101,also Q205 and Q206,and the fuse on the underside between C204 and Ce101.If you have done these,then it would seem to indicate a faulty CCFL,as suggested,or, I presume you have checked the resistance of the output transformer feeding the ccfl skts,and both secondaries are equal + or - 5% ??

[retiredcaps]

Re: Fixing a DAC-19M005 Power Supply -parts are in

I've pulled the CCFL plugs one at a time and turned unit on and get the same on for a bit then off, so I think its not in the lamps, but a component providing the high voltage to them is blinking out.

Almost all lcd monitor inverter chips will purposely do 2 seconds to black if only one ccfl lamp/wiring is bad. That is, it is all or nothing approach when it comes to turning on the ccfl. Thus, if you only have one ccfl plugged at a time, the lcd will go 2 seconds to black.

The test that you have done is "valid" if the ccfl is completely cracked or the wiring is completely broken. Or if you can tell a noticeable difference in brightness.

So you could still have a ccfl lamp or wiring problem. The easiest way to eliminate the ccfl is to use a spare/good ccfl.

BTW....> I got my parts from Digikey ..ordered PM the 24th..here the 27th AM..you just can't beat them !

There are many days that I wish Canada had a better online experiences like in the USA.

[kingofcoins]

Re: Fixing a DAC-19M005 Power Supply - new pics

Here's the new pics after the restoration attempt

[kingofcoins]

Re: Fixing a DAC-19M005 Power Supply -parts are in

I've installed the new Mosfets at Q205 and Q206 , replaced the ruined cap, and repaired the traces and pads, and did some re-soldering....this was a no power, no lights unit, now to be used on a Chi Mei A190A2 LCD, which is like an Acer 1916 and others.
Now it powers up, the green led light stays on, the screen goes to normal desktop then goes black. Turning monitor off and back on repeats the '2 seconds to black' thing. The DC power stays on steady at 11.6V and 5.0v to logic board.
I've pulled the CCFL plugs one at a time and turned unit on and get the same on for a bit then off, so I think its not in the lamps, but a component providing the high voltage to them is blinking out.
Two other things of note I replaced CE107 cap near the with a 47uf x 50v used one from another power supply as the oem had a 3.6 ESR and the used one only 0.34. There is also a 33uf x 25v cap near the Q102 transistor that read a low ESR in circuit so I didn't change it out.
Am I now to diagnose the inverter circuit ?
Is that fuse F200 that has been a popular fault at issue here...?
Open to suggestions on what to check next, thanks !


BTW....> I got my parts from Digikey ..ordered PM the 24th..here the 27th AM..you just can't beat them !

[kingofcoins]

Re: that F102 resistor fuse

Retired...
Finally dawned on me when I measured that same resistor on a Westinghouse LCM 19v7 I'm fixing and got 100 ohms...that's three in a row the same value.
Looking at both of mine again I realized our 'orange' is actually brown, which means brown black brown gold is 100 ohms, and all of our F102 'fuses' are good.
Must be my eyes, or the "Holidays".

Cheers guys !