Monitor not turning on, board looks burnt

[tsume]

I have a Viewsonic 19" display. The board marked Mirage Electronics Co, LTD PI-190DTLB has a scorch mark on it and two caps that looked bulging. I replaced the caps, but the display still will not power on at all. No power indicator light, no display, nothing. I checked the fuse and it's working. This problem happened twice in the past where the monitor would just randomly not power on, but usually it would work fine the next day.

This poster took pictures of this exact board which has the scorchmark in the same exact spot:
https://www.badcaps.net/forum/showthread.php?t=9464
The capacitors that were bulging that I replaced were the two within the yellow oval. Would the transistors labelled 3055 6G underneath the scorch marks be the potential issue, and if so is there a part number I can order from digikey to replace them? I'm totally lost on this one.

[retiredcaps]

Re: Monitor not turning on, board looks burnt

1) Please post pictures of your power and logic board. There may be problems specific to your board so that is why we like to see pictures of your board.

Please use the manage attachments button to add pictures like the other thread.

2) Do you have a multimeter? If yes, do you get any voltages on CON203? Report what you get for each pin.

[tsume]

Re: Monitor not turning on, board looks burnt

Since my first post, I have replaced the two transistors with AOD442 and still am having the same issue. Per request, I have posted the best pictures I can get of the board in this reply. To answer question 2, I am not reading any constant voltage on any of the pins on CON203. The numbers on my multimeter occasionally jump up to read between 1-2 volts but only for a second then it goes down to less than 0.1. I do hear a sound like a capacitor discharging about once every second but I cannot tell which cap it is. When the monitor is all put back together, the speakers make a quiet "pop" sound about once every second in sync with the capacitor sound. This starts as soon as power is connected - pressing the power button has no effect and indeed it happens when the only thing connected to the board is the power cable.

[retiredcaps]

Re: Monitor not turning on, board looks burnt

I am not reading any constant voltage on any of the pins on CON203.

Your photo is a bit blurry and we cannot make out the legend for CON203.

Can you list each pin and the measured voltage? Something like this?

pin 1 - legend says 5V, measured 3.4V
pin 2 - legend says GND, measured 0.0V

The "small cap" (C206 from the other thread with a better picture) just below the big cap in your picture plays an important part of the SMPS startup process. These caps can be bad without visible signs of bloating.

[delaware74b]

Re: Monitor not turning on, board looks burnt

^x2 on C206. I believe that cap is used to start-up the standby voltage section.

Also, your output caps (lower left corner of your second photo) look like Fujiiyyu's. Replace all caps except for the primary cap (I'd use Panasonic FM or FC's) and test output voltages.

[jetadm123]

Re: Monitor not turning on, board looks burnt

Sounds like your power supply is trying to start, but can't. Try measuring the voltage across the large 450v? cap, C201. If you're in the USA, you should read approx. 165 VDC. If you get this voltage, then measure the voltage across the cap that retiredcaps mentioned, C206. What is the voltage? FYI- C206 is connected to pin 6 of the PWM controller, IC201.

[PlainBill]

Re: Monitor not turning on, board looks burnt

Since my first post, I have replaced the two transistors with AOD442 and still am having the same issue. Per request, I have posted the best pictures I can get of the board in this reply. To answer question 2, I am not reading any constant voltage on any of the pins on CON203. The numbers on my multimeter occasionally jump up to read between 1-2 volts but only for a second then it goes down to less than 0.1. I do hear a sound like a capacitor discharging about once every second but I cannot tell which cap it is. When the monitor is all put back together, the speakers make a quiet "pop" sound about once every second in sync with the capacitor sound. This starts as soon as power is connected - pressing the power button has no effect and indeed it happens when the only thing connected to the board is the power cable.

Classic symptoms of a problem with the SMPS controller.

1. Replace the small electrolytic cap next to the SMPS transformer (The SMPS transformer is T201).

2. If you replaced the cap, try unsoldering one end of F203.

3. If it still doesn't work you most likely have a shorted diode on the output of the SMPS.

PlainBill

[sabre504]

Re: Monitor not turning on, board looks burnt

Hi all this is the same board as used in the phillips x19

Parts i have used to repair on these

MTD3055VLT4 N-Channel Power MOSFET 60V/12A, DPAK
(compare these to what you have used )

4 x 680uf 25v Caps
2 x 470uf 25v Caps
3 x 220uf 25v Caps
1 x 10uf 50v Cap
1 x 22uf 50v Cap

Hope this helps

[tsume]

Re: Monitor not turning on, board looks burnt

pin 1 - says BLON (ELON or 8LON maybe, hard to read) - 0
pin 2 - says GND - 0
pin 3 - says GND - 0
pin 4 - says BRI - 0
pin 5 - says +5V - 3.5
pin 6 - says +5V - 3.5
pin 7 - says GND - 0
pin 8 - says GND - 0
pin 9 - says 14V - 14
pin 10 - says 14V - 14

C201 (big cap) - multimeter doesnt go above 200, cap says 450v, so i didnt try it.
C206 (little cap) - 11-13v, it fluctuates
The caps at the bottom left are all Fujjiyyu except the black one.

I will get a replacement for C206 and post back the result.

[retiredcaps]

Re: Monitor not turning on, board looks burnt

pin 1 - says BLON

BLON is correct. backlight on, I believe.

pin 5 - says +5V - 3.5
pin 6 - says +5V - 3.5
pin 9 - says 14V - 14
pin 10 - says 14V - 14

As you can see the 5V rail is not coming up properly which means the logic card isn't getting the correct voltage it needs to operate

C201 (big cap) - multimeter doesnt go above 200, cap says 450v, so i didnt try it.

The 450V cap is the maximum rated. Like jetadm123 wrote, it is likely only to be 165V DC across that cap, but since your multimeter only goes to 200V, it was a wise choice not to measure it because some power supplies have a PFC which would put it around 320V DC.

C206 (little cap) - 11-13v, it fluctuates
The caps at the bottom left are all Fujjiyyu except the black one.

The C206 fluctation is a sign that the cap could be bad.

Fujjiyyu doesn't have a great reputation on this site so most here will suggest you recap all the electrolytic caps except the largest one which rarely, but not never, fails.

Members here will recommend Panasonic FR, FM, and FC caps (in that order of preference).

[tsume]

Re: Monitor not turning on, board looks burnt

The C206 fluctation is a sign that the cap could be bad.

Replacing C206 resolved the issue.

Will also look at replacing all the Fujjiyyu caps so I don't have future problems. Thanks everyone for all the assistance!

[retiredcaps]

Re: Monitor not turning on, board looks burnt

Replacing C206 resolved the issue.

Will also look at replacing all the Fujjiyyu caps so I don't have future problems.

Good to hear. Yes, replace all those caps and you should have a problem free monitor for years to come.

[electronza]

Re: Monitor not turning on, board looks burnt

Replacing C206 resolved the issue.

Will also look at replacing all the Fujjiyyu caps so I don't have future problems. Thanks everyone for all the assistance!

Just to say that I had the same issue on a Packard Bell Maestro 220Wdv monitor with the same invertor board part number PI-190DTLB.
Replacing C206 solved it for me too.
Thanks for the help!

[Pauldesign]

Re: Monitor not turning on, board looks burnt

Originally Posted by tsume
Replacing C206 resolved the issue.

Will also look at replacing all the Fujjiyyu caps so I don't have future problems. Thanks everyone for all the assistance!

I concur with Tsume and electronza

The same PSU, the same issue and the same solution!

I was even told by the LCD plastic label Manufacturer (Sahara) to buy a new monitor as the PSU is obsolete and can't be repaired nor replaced.

Thanks to the forum owners and to those that posted on this issue and related issues; you guys just saved me some money, time and frustrations