HP L1906 Monitor

[Firestorm213]

Recently aquired a HP L1906 monitor that wouldn't power on at all.

Replaced three caps on the board and monitor comes right up. Picture is crisp and clear with no flickering.

However the buttons for the menu and power do not work. The monitor comes up in a power on state. Can not be shut off without unplugging the power. I have tested the buttons they do complete the circuit like they are supposed to.

Another intersting problem. Monitor will only recognize video signal if it is present when power is plugged in. If I disconnect the monitor cable while the power is still on the monitor goes blank as expected but when I plug back in the monitor cable the monitor remains blank.

The LED light on the monitor remains green rather a video signal exsist or not.

Any thoughts?

[smason]

Re: HP L1906 Monitor

Replace more caps?
It's possible that even if they look ok, more caps are bad. Symptoms can be almost anything, as ripply power can do weird things.

What brand are the caps in the power supply/inverter board?

What brand/series did you replace them with?

[retiredcaps]

Re: HP L1906 Monitor

Replaced three caps on the board and monitor comes right up. Picture is crisp and clear with no flickering.

1) Did you replace all the capacitors on the board or just the ones that were visibly damaged? What brand and make are the replacement caps?

2) Do you have a multimeter and do you know how to use it?

3) Post clear focused pictures AFTER reading

https://www.badcaps.net/forum/showthread.php?t=1868

Please do not post pictures inline.

Take your boards to a window on a sunny day, turn flash off, and use macro mode. Take a top down view of all your boards (front and back). Make sure the photo is legible so that we can read the PCB printing clearly. A shutter speed of 1/125 or faster will produce nice clear focus pictures. Try to get a photo that is 2000x2000 resolution or as close as possible.

Here is an example of the pictures we want.

https://www.badcaps.net/forum/showpos...94&postcount=1

[jetadm123]

Re: HP L1906 Monitor

I suggest you post some photos of the control button board along with some photos of the power supply and logic boards per the link below:

https://www.badcaps.net/forum/showthread.php?t=1868

In the mean time I suggest you try reseating the cable that connects the control board to the logic board.

[Firestorm213]

Re: HP L1906 Monitor

Things I have replaced so far. I replaced three capacitors, all were CapXon brand 1000uf 10v.

C824 & C822 were replaced with RLP brand1500uf 10v caps. C823 was replaced with nichicon brand 1200uf 10v. (Probably bad practice but I'm working with parts that I have avaialable)

I have a multimeter, see last pic, and I'm pretty familiar with it but don't doubt that you probably could teach me a thing or two.

Thanks for you help on this.

[retiredcaps]

Re: HP L1906 Monitor

Things I have replaced so far. I replaced three capacitors, all were CapXon brand 1000uf 10v.

C824 & C822 were replaced with RLP brand1500uf 10v caps. C823 was replaced with nichicon brand 1200uf 10v. (Probably bad practice but I'm working with parts that I have avaialable)

Never heard of RLP, but all the 3 original Capxon caps add up to 3000uF (if in parallel). But you replaced with 1500+1500+1200 = 4200uF.

I would try getting the right caps (3x 1000) from Panasonic, Ruybcon, or United Chemicon and then retesting.

These caps provide the 5V DC to the logic card. I'm guessing if the values are off, it may affect some of the functionality of the logic card?

BTW, excellent pics.

[kc8adu]

Re: HP L1906 Monitor

rlp is an ost series.

[retiredcaps]

Re: HP L1906 Monitor

Some other suggestions.

The video chip is found at as per dasjeetu (from yesterday - how timely)

https://www.badcaps.net/forum/showthread.php?t=11095

I have no experience in this type of chip interface, but they are documented in the first 7 pages. I'm not sure which pin you would have to monitor for the on/off switch. (BTW, jetadm123 wanted pics of the control button board).

If there is no voltage or incorrect voltage to that pin, then you can traceback each component to the source?

[viziks]

Re: HP L1906 Monitor

Hi,I have replaced these 3 caps on 20 such monitors and all have worked with only this replacement.
I have 1 more of this which has no Display.

I am looking for a schematic,I could find only AOC versions ,this says PX849A but I cant find any schematic.
It uses 2 FETs in Inverter Q104 D413 and Q105 D454 of which Q105 shows short between D and S in circuit but FET chck Ok on disonnecting Source (S) of FET.

Any help would be appreciated .
A schematic would be most helpful.

Samir

[selldoor]

Re: HP L1906 Monitor

@Viziks
https://www.badcaps.net/forum/showthread.php?t=39740


Also PX849A seems to be an L1706 have you got the wrong thread??
If so and your boards are not like those pictures above please start a new thread.