Hp 2159M Bad display

[Mr Bill]

The main 4A fuse was blown when i got this monitor. Changed out the fuse and this is what i see. I checked the fuse on the t-con and it measures 0.3ohm. The main board is full of capxon caps. Can a bad cap cause a display like this or am i looking at a failing lcd panel? I ordered a Peak Atlas 70 ESR meter on monday so when i get it i can check the capacitance and esr of the caps on the main board.

Just seeing if anybody has had any similar situations.

Thanks

Edit:
I did clean and reconnect the 30 pin cable going from the main board to the screen

[jetadm123]

Re: Hp 2159M Bad display

Could be caps. However, I suggest you try measuring the output of the voltage regulator, U201 (located right side middle of board). Use a mounting screw for your ground probe and measure voltage at each pin.

[retiredcaps]

Re: Hp 2159M Bad display

1) If you bring up the on screen menu, does it shows the same problem?

2) On the main board, there are two voltage regulators U201 and U202. They look like they have been replaced by someone because the tab doesn't fit the pcb silkscreen?

3) You should check U201 and U202 to see if they are outputting the correct voltage as well. It looks like U201 is a 3.3 and I can't make out U202 despite the excellent photo.

4) And yes, Capxon makes crap caps.

5) jetadm123 beat me re the U201, but not the U202!

[jetadm123]

Re: Hp 2159M Bad display

5) jetadm123 beat me re the U201, but not the U202!

Good catch!

[Mr Bill]

Re: Hp 2159M Bad display

Here are my results...

If i pull up the menu it looks nasty too.

The 2 voltage regulators (U201, U202) are part # AX1117, i uploaded the datasheet for you. Using the ground pin here are my results.

U201
V-in 3.301 volts
V-out 5.15 volts

U202
V-in 3.575 volts
V-out 1.796 volts

Both are the same part number. I also got the same readings using the ground pin on the connector coming from the power board.

[Mr Bill]

Re: Hp 2159M Bad display

Well...............

I went to turn my test computer off and now the display is perfect..

When i did the readings i taped cardboard to the back of the screen and then the power and main boards were taped to the cardboard. When i stood the monitor up to power off the computer the monitor slid a little bit on top of my tower. When i caught it my fingers "bumped" the vga d-sub connector.

And here we are.

I'm wondering if the vga cable i was using has a loose connection in it. I used a different cable and i'm pulling, wiggle, slapping and i'm not getting the crappy display now. I'm going to try the "suspect" vga cable on a known good monitor tomorow and see if i get the same results.

[Mr Bill]

Re: Hp 2159M Bad display

UPDATE

Its not the vga cable. Just messing around with the resolution it would go from good to bad then back to good. I'm thinking its in the mainboard itself.

The 2 voltage regulators are actually 2 different parts. (reading the entire datasheet helps )

U201 is the 3.3 volt out with a 4.8 volt input. I'm getting 5.15 volt in and 3.301 out.

U202 is 1.8 volt output with a 3.3 volt input. I'm getting 3.575 in and 1.796 out.

On both regulators i'm right in tolerance for the output but a little high on the input. I'm not sure if the .275 to .350 volt difference would define it as bad. It seems that if i turn the monitor on and off several times thats when it goes bad then back to good. So if i ever get my esr meter i'm going to start checking the capxon caps that are on the mainboard. If i find even 1 bad cap i'm just going to recap the entire mainboard.

[Scenic]

Re: Hp 2159M Bad display

Check each of those regulators (output voltage) when the image is messed up. One of them might be on its way out, but sometimes working normally.

I've seen that happen before. In my case, the 1.8V regulator for the main controller IC sometimes dipped down by 0.2V on the output, causing all kinds of glitchy-ness..

[sabre504]

Re: Hp 2159M Bad display

Hi had the same with a regulator on a board ok when cold on startup till you turned it off then no joy till you pushed down on it .
I assumed that the pressure helped make the connection but this was cured by replacing

[Mr Bill]

Re: Hp 2159M Bad display

I checked the outputs of the voltage regulators with the display distorted and i'm still getting 1.796v and 3.301v.

I did check every capxon cap in the main board and all of them had an esr of less than 1 ohm. I also checked the 5v going to the t-con from the main board on the lvds cable and i'm getting 5.04v. I then checked the fuse on the t-con and it measured 0.001 ohm with 4.97v going through it with the monitor on.

Now there apears to be 2 (maybe) mosfets that may drive the lcd panel (Q3 & Q4). On Q4 Putting my black probe on pin 7 of the lvds cable (ground), i'm getting 4.99v, 12.49v, 4.92v

And on Q3 i'm getting 4.92v, 0.000, 4.98v

I don't know if the missing 12 volts from Q3 could be my problem, i tried checking for shorts but i'm getting well over 30 ohms. The side of the tcon that these 2 mosfets are on is the more distorted side of the monitor.

The part numbers are
Q3
81 Y917

Q4
92 Y914

I tried finding a datasheet but i'm coming up empty.