HP no backlight

[jetadm123]

Re: HP no backlight

Ah, I misunderstood your initial voltage readings for on/off. Looks like the main board is sending the correct 3.24V to turn on the backlights. Disregard my initial comments regarding I308.

Going back to Q104 and Q105. What voltage readings are you getting when you measure pin 3 (S1) on Q104 and Q105?

[davg]

Re: HP no backlight

Thanks jetadm123 Pin 3 (S1) Q104-Q105 both read 26.2v Black lead on ground screw red lead on pin 3, connected to running PC

[jetadm123]

Re: HP no backlight

Good. At least we know those transistors have access to power to perform their switching actions.

In the top middle of your power supply photo:

With power off and monitor unplugged, try checking transistors Q106 and Q107.

With your meter set to 200 ohms, place your meter probes across:

E-B
B-C
E-C

Reverse your leads and perform the same checks again.

You may have to set your meter to a higher resistance setting to see a valid reading.

[davg]

Re: HP no backlight

Q106 reading EB 51.7 k BC 151k EC 99k both ways Q107 EB 99.4k BC 16m EC 16m reversed EB 99.4k BC 16.5M EC 16m (meter set to auto)

[jetadm123]

Re: HP no backlight

Doesn't look like anything is shorted. Looks like we will have to move on to the ccfl controller, I101. Fortunately, it's only 8-pin. Measure the voltage at each pin. What's the part number of I101? Note: I have to run some errands and will be gone several hours.

[davg]

Re: HP no backlight

The markings on (I101) is Line 1- OZ9930D, Line 2- 43279731G Line 3- 0505A The voltage readings are as follows: With the indicator mark north and pin 1 immediate left and pin 8 immediate right Pin 1- 2.4v pin 2- 0.08v pin 3- 0.01v pin 4- 0.01v pin 5- 0.01 pin 6- 3.8 pin 7- 1.9v pin 8- 0.05v

[jetadm123]

Re: HP no backlight

I'm in a holding pattern right now because I can't seem to locate a data sheet for the OZ9930.

[davg]

Re: HP no backlight

I have searched and can't seem to find one either. Closes I could find was OZ998 Thanks

[retiredcaps]

Re: HP no backlight

I'm in a holding pattern right now because I can't seem to locate a data sheet for the OZ9930.

https://www.badcaps.net/forum/showthread.php?t=8907

may help?

[jetadm123]

Re: HP no backlight

Thanks retiredcaps. It does shed a little light on the subject by identifying which pin is which. Only problem is that we still don't what the minimum voltage(s) are required to make the OZ9930 run correctly.

[budm]

Re: HP no backlight

Did anyone find the place to download the spec sheet?

[davg]

Re: HP no backlight

According to that drawing It would appear I should have 5v on pin 7 and I am recording 1.9? or is something else in that circuit effecting that voltage?

[retiredcaps]

Re: HP no backlight

VDDA, in other OZ9 datasheets, is typically 5V DC. If it is low, then it could be that the OZ9 pwm is some sort of protection mode (over voltage, open lamp protection).

I suggest measuring the secondary windings (in red and yellow) on the inverter transformers to see if open is open. Post your resistance measures for both colors.

[budm]

Re: HP no backlight

OK, after looking through my HP pictures collections, this HP VS17 uses the same power supply/inverter board as VS19/D.
Here is the service manual, the sch seems to match your board. It also has good explanation how it works.

[davg]

Re: HP no backlight

Thanks retiredcaps these two points are reading .458k and .454k
Thanks budm great information and will require much study. Great troubleshooting section. Don't put away your HP pictures yet because I have a HP f2105 that I have been trying to find a service manual for if I may be so bold??

[jetadm123]

Re: HP no backlight

Thanks budm for the service manual, it helps a lot.

davg- on the VS19 service manual, go to page 15 for troubleshooting the inverter circuit and try taking some of the recommended voltage measurements.

[budm]

Re: HP no backlight

davg, I hope if you do not mind, I post your pictures of the boards on my Photobucket.
By the way, the HP F2105 are know for having bad lamp assemblies and bad LCD panel (vertical lines), I had done 5 of them, all with bad lamp assemblies.
http://s807.photobucket.com/albums/y...HP/HP%20F2105/

[davg]

Re: HP no backlight

Thanks jetadm123 I have been away but will get some readings as soon as I get back on track. Question on the trouble shooting page check voltage on pin C112 is that across the cap c112?
Thanks budm truly appreciate it. This f2105 do have lines but they are shadows of the objects on the desktop and a very slow refresh rate. Takes the mouse for ever to move from one point to the other? I will start another thread on that one later

[jetadm123]

Re: HP no backlight

I see what you mean. Since they say "pin", it sounds more like a test point, but I'm not sure. However, I think most members agree it's an inverter problem and I would go on to the next step, checking pin 6 of I101. You read 3.8V versus the suggested 5V (I don't know what the min VDD is for the OZ9930). The flowchart says to check R105 and C112. I think it's a typo and they meant C102 instead of C112, since C112 is not part of the VDD circuit.

[budm]

Re: HP no backlight

Can I get the resistance reading of each pin of the PWM IC OZ9930 and Ground?