failure point in Viewsonic VT2230-M

[kturnerga]

I have a VT2230-M TV that displays the Viewsonic bird bitmap then displays no image though you can see the backlit screen (no words readable even if up close) . I cannot turn it off by the power button, which stays lit all of the time. All but one of the caps (630UF 35v) was replaced on the power supply. I think it is the main board. As the main boards are as rare as hen's teeth I wonder if there is a common failure point I can remedy easily or do I just need to wait for a decently-priced board? The caps look good on the main board and they looked good on the power board. This has me puzzled.

Thanks
KT

[budm]

Re: failure point in Viewsonic VT2230-M

If you can post the pictures of all the boards, that will help.
On the main board, I would check the voltages of the regulator IC's first.

[kturnerga]

Re: failure point in Viewsonic VT2230-M

I did not see any reg chips on the main board (the I/O board) but did see three or four on the power board. The yellow board is the power and the green is what I call the main board.

[selldoor]

Re: failure point in Viewsonic VT2230-M

Not sure if you are saying the backlights stay lit but no picture or backlights go out but can see faint picture. I would replace that last cap ? what brand/series caps did you use for replacements.
With it all connected up lease check the voltages on the connectors and list results
eg CN1
Pin 1 5v Actual 4.9v
Pin 2 5V Actual 5.1v
Pin 3 PSOn 1.2v etc etc

Try and do it once when it has reached its stable not working stage and with a few attempts when it is trying to come on. On the PSON be measuring it when you press the on button and report if it changes. Although low voltages being measured take care as parts of the board could be at 300-400 volts.

Q30 is a LD1117A Voltage regulator - can you test for shorts (see 2 seconds to black guide link below)and the voltages - use a ground screw for the negative probe and check the 3 pins
left to right - ignore the fat tab. Post results




Next as you did get a picture flash can you check the secondary windings on the inverter transformers POwer Off meter on ohms 2000. I m not sure which pins as you have not posted pictures of the bottom of the boards.

It may be just the 2 pins on their own at the end we cant see or

IF your transformers look like the one in this picture then it is beteen S1 and S2 If it is neither of these you will need to go around all the pins in turn 1 to 2 1to3 then 2 to3 2 to4 and so on until you have done them all. Unless you can find a part number and datasheet. You are most likely looking for between 400 and 1800 ohms

Read this (start at post 19)
https://www.badcaps.net/forum/showthread.php?t=10419

Please can you update you profile with country and mains voltage.

[kturnerga]

Re: failure point in Viewsonic VT2230-M

I get the Viewsonic logo for about five seconds then the backlight stays on with no pic or even a NO SIGNAL. I may test the regs or just replace them. I am leery of testing live gear though techs tend to do that on a regular basis.

USA; nation
110V AC

[retiredcaps]

Re: failure point in Viewsonic VT2230-M

I did not see any reg chips on the main board (the I/O board) but did see three or four on the power board.

Q30 is a voltage regulator on your main board. It looks like an LD1117A.

edit: oops didn't see that selldoor already had it covered in post #4.

[selldoor]

Re: failure point in Viewsonic VT2230-M

"I am leery of testing live gear"

Ok if your not going to do live testing, I can understand that but I think you are on the wrong forum. If you are going to replace parts without testing you may as well just replace the board.

[ben7]

Re: failure point in Viewsonic VT2230-M

Uh-oh! I see some fake Nippon Chemi-con caps in the PSU which look suspicious, they have X vents instead of the Y vent.

[retiredcaps]

Re: failure point in Viewsonic VT2230-M

Uh-oh! I see some fake Nippon Chemi-con caps in the PSU which look suspicious, they have X vents instead of the Y vent.

Great catch. Now that I look again, I should have noticed that.

[kturnerga]

Re: failure point in Viewsonic VT2230-M

"I am leery of testing live gear"

Ok if your not going to do live testing, I can understand that but I think you are on the wrong forum. If you are going to replace parts without testing you may as well just replace the board.

I'll be sure I'm not alone at home when I test it live should I tangle with the 110v by mistake.

I also bought the caps off Ebay (the fake Chemicons). Little did I know.
I tested the 1117; it does not have a short and the voltage (may have it bass ackwards) is Pin 1; 2.89v; Pin 3; 5v.
There is a mild whine from the area of the power supply as if that is meaningful.

[selldoor]

Re: failure point in Viewsonic VT2230-M

Ok, Im no tech and have 250 volts to contend with.Most of the testing is low voltage - you will usually be told if high voltage is involved.
Oddly your PS Board does not seem to be marked with High Voltage area - I have marked them roughly on the picture and you shouldnt touch heatsinks.

You could even make a card cap to cover most of it while you are working. Main board has only low voltages.

Whilst the caps will need replacing,good spot Ben7, you can continue with some tests.

You have not told us what pin 2 measured on the 1117a.

I suggest you do the inverter transformer secondary windings next,(see post 4). If they have gone and you cannot find replacements there is little point in replacing the caps.

[retiredcaps]

Re: failure point in Viewsonic VT2230-M

I'll be sure I'm not alone at home when I test it live should I tangle with the 110v by mistake.

Good precaution. I normally use insulated aligator clips when measuring something high voltage. That way, I can make the measurements hands free and have everything plugged into a power bar that I can safely switch on and off.

It also helps if you have a quality multimeter with some input protection.

I also bought the caps off Ebay (the fake Chemicons).

99% of the caps on ebay are fakes. It takes a trained eye and test equipment to know the fakes from the real ones.

Stick with name brand distributors like digikey, mouser, or the badcaps.net store where you are guaranteed to get the real goods.

[kturnerga]

Re: failure point in Viewsonic VT2230-M

Both transformers ohm at .2 on p1 and p2 and at 1 on S1 and 2.

[retiredcaps]

Re: failure point in Viewsonic VT2230-M

Both transformers ohm at .2 on p1 and p2 and at 1 on S1 and 2.

For S1 and S2, you want your manual multimeter set to the 2000 (2k) ohm scale. Report your readings with this new scale.