Gaurdall G-LCD19B

[sabre504]

Re: Gaurdall G-LCD19B

Yes all the volts appear right until you get to 1.8 regs.
So as i say try a change of caps start with the 16v 10uf.
Mind you am eyeing up the guts of my Xerox 19" wondering if i could rig them up in the casing if all else fails

[seanc]

Re: Gaurdall G-LCD19B

All sounds OK to me!

[sabre504]

Re: Gaurdall G-LCD19B

Thats a volt reg getting 4.99 on the 5v side and 3.3 on the other

[seanc]

Re: Gaurdall G-LCD19B

Tried the caps above that, to the left and right of some sort of black component?

[sabre504]

Re: Gaurdall G-LCD19B

Should have said
all bigger caps are 16v 100uf
3 small caps 16v 10uf

[sabre504]

Re: Gaurdall G-LCD19B

Volts across legs 12.23

[seanc]

Re: Gaurdall G-LCD19B

Measure the voltage going across the cap above the VGA connector.

[sabre504]

Re: Gaurdall G-LCD19B

Hi see you were near

well think i might change them all got nothing to lose, but will hold off till tomorrow see if can find anything else with a bit of prodding about.
Not holding out much hope as i think apart from caps have been thro everything apart from the chips

[seanc]

Re: Gaurdall G-LCD19B

Ahah, you now have a location showing - you're somewhere near me

So yes, the caps could be causing this problem.
I had a 17" monitor with external 12v PSU, the monitor had gradually taken longer and longer to turn on, then wouldn't turn on at all.

Investigated the PSU - putting out 12v as expected, tested with another just in case - still dead.

Tested ESR of the small 100uf 16v caps, starting nearest the power jack - very high ESR.
There were about 3 caps in parallel there, I changed those 3.
Worked fine afterward

[sabre504]

Re: Gaurdall G-LCD19B

Well the parts arrived fitted and still showing 1.95v.

Just debating with myself whether the caps could be doing this as i seem to be getting voltage readings off the top of the caps (not sure if this is usual never done it before ).

[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

[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

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

[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

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

[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

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)

[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

[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.