Gaurdall G-LCD19B

[sabre504]

HI have a problem with this unit .
Not sure if its a caps problem but thought someone may have a clue as to the problem.
Firstly when power is applied (12v 4a) the screen lights up so inverter working ok .
Took out lcd panel and tested on another unit and it works fine .
Disconnected the control switch panel and it still powers up so something is amiss on the control board.
Looked online but cannot find a data sheet for the board so just wondered if anyone had come across this board (VA-3700 VER:1.1) or a similar problem before.
Have uploaded a pic just so you can see it not a good one need batteries for camera had to use phone.
Any help or input appreciated

[pedro]

Re: Gaurdall G-LCD19B

HI have a problem with this unit .

And I'm sure that you'll eventually tell us what it is, but in the description you posted I can't detect one.

Not sure if its a caps problem but thought someone may have a clue as to the problem.
Firstly when power is applied (12v 4a) the screen lights up so inverter working ok .
Took out lcd panel and tested on another unit and it works fine .

So there's no problem there ....

Disconnected the control switch panel and it still powers up so something is amiss on the control board.

Why do you presume this. Many many monitors power up in the "ON" state without user intervention. With the front control panel disconnected, I'd expect it to "get up and go" normally.

Looked online but cannot find a data sheet for the board so just wondered if anyone had come across this board (VA-3700 VER:1.1) or a similar problem before.
Have uploaded a pic just so you can see it not a good one need batteries for camera had to use phone.
Any help or input appreciated

Pictures may help, but so far I'm in the dark as to what isn't behaving properly.

[sabre504]

Re: Gaurdall G-LCD19B

The monitor shows only white screen but as i said that tested ok on another unit.
The switches do nothing when connected but all the pins where the switch panel connects show voltage except the earth pin so the inverter runs constantly it is possible that someone has put in a new inverter board and not wired it correctly.
Have checked voltages on other parts to see if supply is going in and out but these have been checked against data sheets for the individual parts and not data sheet for the board.

I will post a pic of the whole set up when i get camera working

[sabre504]

Re: Gaurdall G-LCD19B

Just a quick pic till i get better one

[seanc]

Re: Gaurdall G-LCD19B

Have you ruled out the cable connecting the LCD to the main board?

[sabre504]

Re: Gaurdall G-LCD19B

Have checked the wires and they are working (have continuity from one end to the other s assume its ok

[jetadm123]

Re: Gaurdall G-LCD19B

You say you took out lcd panel and it tested good on another monitor. Was that monitor also the same model as the one in question? If yes, have you tried swapping the logic/video card from the "good" monitor to see whether or not the card is the problem?

[PlainBill]

Re: Gaurdall G-LCD19B

I'm assuming you have verified the external power supply is good. If so, a better picture is a good idea. I can identify two voltage regulators, and there is at least one and possibly two more candidates. verifying they are working would be the next order of business.

PlainBill

[sabre504]

Re: Gaurdall G-LCD19B

I have tried 2 seperate power supplies and get the same result.
I know i need better picture will do that tomorrow and will post

I tried the LCD panel in my Xerox unit as this has no screen but comes in handy for testing ,
but i dont have another of these boards cant even find one online it has no makers name or code just VA-3700 VER:1.1 and it is a single sided board there are no components on the back .

But have found the monitor its a professional IT and security monitor (bit of a mix) has 1 vga 2x s vid 2x bnc i think they are called and has a hard glass front quite a nice unit in all

[sabre504]

Re: Gaurdall G-LCD19B

Right better pic now

[jetadm123]

Re: Gaurdall G-LCD19B

Nice photo! At this point, you can do what PlainBill suggested and check the voltage regulators U14 and U21. They appear to be generic 1117-1.8 regulators made by several companies. They are 1.8V output. The large tab and middle leg are Vout (1.8v). Left leg is ground and right leg is Vin (5V?). Can't read the part number on U12, so I'm not sure if it's a voltage reg or not.

[PlainBill]

Re: Gaurdall G-LCD19B

I have tried 2 seperate power supplies and get the same result.
I know i need better picture will do that tomorrow and will post

I tried the LCD panel in my Xerox unit as this has no screen but comes in handy for testing ,
but i dont have another of these boards cant even find one online it has no makers name or code just VA-3700 VER:1.1 and it is a single sided board there are no components on the back .

But have found the monitor its a professional IT and security monitor (bit of a mix) has 1 vga 2x s vid 2x bnc i think they are called and has a hard glass front quite a nice unit in all

Excellent picture. There are a number of things that are unusual about this monitor. First of all, the blue connector - is that a standard high density DB15 (VGA) connector?

Next, I have identified 4 voltage regulators. I've circled them in red. The two on the left side (U21 and U14) are the more significant. They appear to be 1117-18 regulators. I've seen a high failure rate on these. The two on the right side should also be checked. The one on the extreme right appears to be a 5V bucking regulator; U12 may be a 3.3 volt regulator. I suggest using the screw next to the bucking regulator as the ground point.

I've been able to identify the function of several of the ICs including U15 (A/D video converter) and U22 (audio amp), but it is difficult reading the part numbers of U18, U12, and the one in the lower right appears to be obscured by a camera strap. What are they?

PlainBill

[sabre504]

Re: Gaurdall G-LCD19B

Hi thanks for help so far
U13 is 1506-50
1 input = 12.13v
2 out = 5.13v
3 Grnd
4 = 4.99 v

U12 is 1084-33pm

input = 4.99v
output =3.33

U14 1117-18

input = 3.33
output = 1.79

U21 1117-18

input = 3.33
output = 1.95

D3 GW 5819

under the strap is another resistor pack +
1 x 1AMN(Sames as Q3)

[retiredcaps]

Re: Gaurdall G-LCD19B

U21 1117-18

input = 3.33
output = 1.95

1.95V is a bit high for 1.8V regulator. Re-check U21.

[sabre504]

Re: Gaurdall G-LCD19B

Checked it 3 times and again with another meter and getting same readings on all previous measurements.

[PlainBill]

Re: Gaurdall G-LCD19B

Checked it 3 times and again with another meter and getting same readings on all previous measurements.

Check the voltage on the ground pin. It is possible to set these up as adjustable regulators by using a voltage divider to raise the output voltage above ground. 1.95 volts is well above the specified accuracy (1.8V +- 2%). If the ground pin is actually at ground, the regulator may be bad, or there is something else raising the voltage.

PlainBill

[sabre504]

Re: Gaurdall G-LCD19B

Checked the ground pin and there is no reading 0V.
Also placed the Neg probe on the ground pin and checked the output and it still shows 1.95v.
So have to buy a couple of these and replace it and take it from there just have to track some down if they are a common part to go wrong better get a few

[sabre504]

Re: Gaurdall G-LCD19B

Another thing i did check was D3 (Gw 5819) i think it is a barrier diode (not sure though) reading 5v at one end nearest power input (ringed in red) but 0v at the other

[PlainBill]

Re: Gaurdall G-LCD19B

Another thing i did check was D3 (Gw 5819) i think it is a barrier diode (not sure though) reading 5v at one end nearest power input (ringed in red) but 0v at the other

That was a mistake on my part. I was going to suggest you test it, then realized it's part of the 5V supply.

A far the 1.8 volt regulators, those are 'jelly bean' parts - very common, mad by many manufacturers. APX1117 and LM1117 are two variations. Just make sure you get it in the right package.

PlainBill

[sabre504]

Re: Gaurdall G-LCD19B

Thats ok plainbill it tested at 5v so assume that not a problem part.
As for the other part i had noticed that they can come in 3.3v and 5v but will track some down .
Once again i appreciate the help you and others have given me so far , and will update as soon as i get the parts and fit them then see what happens