HP no backlight

[davg]

Re: HP no backlight

Any way, this is the resistance reading of the OZ9930 with the help of lestr:
https://www.badcaps.net/forum/showth...771#post280771
So I am not sure which reading is correct, yours or lestr.

Thanks budm neither am I not sure if the test method was the same because there are great differences.

[davg]

Re: HP no backlight

Thanks retirecaps here are the results for the diodes D116 .948 - .547, D111 .546 - 0L D107 .842 - 0L, D 108 .537 - .696, D114 .549 - 0L, D103 .543 - 0567, D101 .543 - 0L, D120 .547 -.951, D121 .547 - .951, D118 .549 - 0L, D105 .547 - .573, D109 .543 - 0L, D112 .543 - 0L, D113 5.37-.696.
D 116, 108, 103, 120, 121, 105, & 113 look suspect and I have not removed them?? I am checking the transistors first and will report when complete.

[davg]

Re: HP no backlight

Transistors Q101 S-G 0L S-D 20m G-D 0L Q109 S-G .98m S-D .92m G-D 4.62m Q107 EC 0L EB 99.2k CB 15.7m Q102 EC 29.5m EB 29.5m CB 0L Q103 EC 51K EB 31M CB 0L Q106 EC 99K EB 98K CB 197K Q108 SG .90m SD .90M GD 4.5m I have not removed the suspect ones and all test done as per your instructions post #19

[davg]

Re: HP no backlight

I have taken Q101 of the board an it would appear that it is shorted. S-G 0L S-D .67m G-D 0L Q101 is a 2N7000 same as Q109. I don't have a replacement so I can't try it

[retiredcaps]

Re: HP no backlight

Your readings would be a lot easier to read if they were like this

S-G - 0L
G-D - 0.5M
D-G - 0.7M

instead of everything on one line.

[davg]

Re: HP no backlight

Thanks retiredcaps I can see what you mean so sorry. Hope the attachment is easier?

[jetadm123]

Re: HP no backlight

I notice that on some of your resistance readings for transistors, you use "M" versus "m". What's the difference?

[davg]

Re: HP no backlight

I notice that on some of your resistance readings for transistors, you use "M" versus "m". What's the difference?

Just a slip of the finger caplock on?? No difference. My meter is auto and most of the readings were megaohms? I just borrowed a fluke 87 lll from my son and some of the readings are different "not much" Am I correct in thinking that Q101 is shorted because I am not reading 30 ohms or is this normal? I believe Q101 may be a switching transister?? Would that make a difference to the reading?

[davg]

Re: HP no backlight

I notice that on some of your resistance readings for transistors, you use "M" versus "m". What's the difference?

Delete

[retiredcaps]

Re: HP no backlight

If a reading is less than 30 ohms, then it is shorted.

[davg]

Re: HP no backlight

If a reading is less than 30 ohms, then it is shorted.

Thanks retiredcaps just wondering about switching action?? I will attempt to locate one locally but I suspect it will proberly be easier to go to China and bring one back lol

[jetadm123]

Re: HP no backlight

Am I reading your chart wrong? For Q101, you're showing 0L, 0L and 20M. "0L" means "out of range". In other words, I don't see anything that reads less than 30 ohms, indicating a short.

[davg]

Re: HP no backlight

Ha you are right what am I thinking and with Q101 removed the reading is
S-G - 0L
S-D - .67m
G-D - 0L
So I can re solder that back in and start over?? Shoot

[davg]

Re: HP no backlight

Any way, this is the resistance reading of the OZ9930 with the help of lestr:
https://www.badcaps.net/forum/showth...771#post280771
So I am not sure which reading is correct, yours or lestr.

I have rechecked the resistance on I101 using a fluke meter and they are more in line with lestr
pin 1 - 5.54m
pin 2 - 5.57m
pin 3 - GRN
pin 4 - 5.08m
pin 5 - 5.08m
pin 6 - 138 ohm (stable)
pin 7 - 123 ohm
pin 8 - 1.36m
Any concerns in these readings?

[budm]

Re: HP no backlight

Pin 7 is the big suspect right now since there is no any low resistance circuit connected to this pin at all (lestr was getting about 900K Ohms).
It can be c110 (.01uf) may be bad or internal IC at pin 7 is bad. Try removing C110 first, see if it is surface mounted or not? You can try lifting pin7 but that may be difficult to do.

[davg]

Re: HP no backlight

Thanks budm I am not sure I understand your request with respect to C110? C110 is not surface mounted and if I remove it do I try the board without it in place??

[selldoor]

Re: HP no backlight

Cant second guess that but have been looking at the pics. I am not sure
which is pin 7 but if you start at bottom left or bottom right in the attached as pin1then can you check that pin6 and pin7 are not conducting at the solder joints.
Clean the flux off if it is only flux.

[davg]

Re: HP no backlight

Thanks Selldoor that is pin 6 & 7 it was some flux and I cleaned it up still no difference

[budm]

Re: HP no backlight

There is something at pin 7 to make it show real low resistance (123 Ohms) at that pin, you can remove the cap C110 or lift pin 7 off the trace and measure the pin7 solder pad to see if you still get low resistance reading. We are trying to find out what is causing this low resistance reading since there is no component with that low value resistance connected to that pin7.

[davg]

Re: HP no backlight

Thanks budm with C110 removed pin 7 is still reading 123.9 ohms so should I try lifting pin 7?