VA902b Shakey jittery image

[blues]

Hi,

Newbie here, I have a viewsonic VA902b monitor that powers on and shows video output, but the screen looks shakey, jittery, like electrical interference. I chacked all cords and connections and replaced cords, all without resolution. Is this possibly a bad capacitor problem?

[retiredcaps]

Re: VA902b Shakey jittery image

Is this possibly a bad capacitor problem?

Yes, it could be. Take apart the monitor and have a look. Even if it is not, try reseating and cleaning every connector.

[blues]

Re: VA902b Shakey jittery image

I followed your advice, but still experience a problem. None of the caps look bloated or leaking to me. Any suggestions of where to start? I have a 40W iron and a multi-meter. I have attached some pictures, I hope they are clear enough and that I have followed the requirments for uploading.

[selldoor]

Re: VA902b Shakey jittery image

Hi - you have su'scon caps on the power board which is possibly the cause of unsteady voltages. Also on the back of the power board can you check the joints where the mains plug is - it just looks a bit odd in the picture - perhaps you can do a close up.
I dont know if you have worked on open boards before but there are voltages in the region of 300-400 volts so you need to be careful.
First can you measure the voltages at the connector at the top right in pic 2 and post your results. Then do it again with it all set up and working - take care that boards do not touch and you are working on a non conductive surface.

[blues]

Re: VA902b Shakey jittery image

Thanks. Total newbie here, wondering how to test with my multi-meter. Pins 1 & 2 are VCC5V. Do I touch the other end to GND pin 6? Also more pics attached.

[selldoor]

Re: VA902b Shakey jittery image

Yes - you can use 3 or 6 as ground

Set meter on Volts DC - red (positive )probe on pin being tested Black (Negative) probe on gnd.
Thanks for pics - mains pins look ok - trick of the light.

[blues]

Re: VA902b Shakey jittery image

Help can't find replacement cap for 100 uF 450V, anyone?

[selldoor]

Re: VA902b Shakey jittery image

Wouldnt worry about replacing if it doesnt look bulged or leaky the big ones are usually ok.
If it becomes necessary we will come up with a suitable alternative.

[retiredcaps]

Re: VA902b Shakey jittery image

Help can't find replacement cap for 100 uF 450V, anyone?

Lots over at digikey, but before replacing any caps, what are your voltage readings?

[retiredcaps]

Re: VA902b Shakey jittery image

Pins 1 & 2 are VCC5V. Do I touch the other end to GND pin 6?

I prefer to use a ground screw closest to the measurement point. That way, there is no risk of both probes touching and possibly shorting out something.

[jetadm123]

Re: VA902b Shakey jittery image

If you find no issues with the power board, then I would suggest replacing the 6 caps on your logic board. Since these caps have a higher capacitance valure and are physically smaller, they tend to dry out more quickly.

[blues]

Re: VA902b Shakey jittery image

Pins 1 and 2 both read .0005 or was it .005 for both pins with capacitor in-line and power off. I have not yet getermined the readings with power due to my poor lighting. I bought a decent worklamp today, hoping to get readings tonight.

[retiredcaps]

Re: VA902b Shakey jittery image

Circled in red are two voltage regulators.

1) Measure the DC voltage of bottom 3 pins (ignore the fat tab). Use a ground screw on the logic board for ground (black probe).

2) Report the part number and your measurements like

Part number = AL1117-33
pin 1 = 0.0
pin 2 = 3.3
pin 3 = 5.0

[blues]

Re: VA902b Shakey jittery image

Do I need to connect this board to the power board and plug in AC to measure the DC here?

[retiredcaps]

Re: VA902b Shakey jittery image

Do I need to connect this board to the power board and plug in AC to measure the DC here?

Yes connect both boards. All voltage measurements require the lcd to be plugged in and powered on.

[blues]

Re: VA902b Shakey jittery image

They are marked as follows:

Part number AL1117-33 (position of component is below, slightly left)
pin 3 = 5
pin 2 = 3
pin 1 = 0

Part number AS1117-18 (position of component is above)
Pin 3 = 5
pin 2 = 1
pin 1 = 0

The values are read on an analog meter and are not exact. Taken with power on the board.

[blues]

Re: VA902b Shakey jittery image

Sorry, didn't get your response until after I posted. Do you need me to re-take them with the LCD wires connected?

[retiredcaps]

Re: VA902b Shakey jittery image

They are marked as follows:

Part number AL1117-33 (position of component is below, slightly left)
pin 3 = 5
pin 2 = 3
pin 1 = 0

Part number AS1117-18 (position of component is above)
Pin 3 = 5
pin 2 = 1
pin 1 = 0

The values are read on an analog meter and are not exact. Taken with power on the board.

Voltage regulators are usually +/- 1% of their stated output. The suffix in the AL1117- part number denotes the expected output voltage. For example, AS1117-18 denotes 1.8V DC output.

With your analog multimeter readings, both regulators would be bad.

It would help to redo the readings with a digital multimeter.

[blues]

Re: VA902b Shakey jittery image

Part number AL1117-33 (position of component is below, slightly left)
pin 3 = 5.10
pin 2 = 3.30
pin 1 = 0.00

Part number AS1117-18 (position of component is above)
Pin 3 = 5.05
pin 2 = 1.24
pin 1 = 0.00

power was on all connectors connected.

[retiredcaps]

Re: VA902b Shakey jittery image

Part number AS1117-18 (position of component is above)
Pin 3 = 5.05
pin 2 = 1.24
pin 1 = 0.00

AS1117-18 is definitely bad and probably the cause of your shaky images.

The fixed 1.8V regulator is a highly used part so it should be available at your local favourite electronics store. If you have old junk boards, you can look there and reuse the old one. I found one on my old sound card.

Otherwise, order online, but ordering from digikey, mouser, etc is going to cost you $8 USD in just shipping/handling.