Received an HP L1906 - no power. Popped off the back and found several bulging caps. Recapped the power/inverter and power came on - but not backlights. LCD shows faint image - swapped lights to test and still nothing. Connector to logic board - brightness measured 2.67v, on-off 3.25v, 5.17v on 5v connection. Voltage measured near inverter is 24v. Where should I check next? Thanks
Hp L1906 Monitor
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Re: Hp L1906 Monitor
Do all tests with power off and lcd unplugged. All tests can be done "in circuit". Set your multimeter to 200 ohms (if manual).
For the yellow components, measure the resistance between pins 1-2, 1-3, and 2-3.
For the red components, look up the part number and find its datasheet. Then test source-drain, source-gate, and gate-drain.
Any reading under 30 ohms suggests a shorted component. To verify, desolder and retest.
PS. Excellent clear focused pictures.--- begin sig file ---
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Re: Hp L1906 Monitor
The 4 pin dip circled in the middle is the PWM IC for the inverter circuit. Don't worry about that.
The driver transistors are the 4 pin dips closest to the inverter transformers.
Get their part numbers and look up the data sheet for a pinout so you can test them.Elements of the past and the future combining to make something not quite as good as either.Comment
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Re: Hp L1906 Monitor
Finally had time to sit down and check things out. Items in red, P607 BD6F2P at Q104 & Q105 - checked pin 1 to all other pins, the only pin that did not appear open was 1 to 3, 15 ohms on Q105, 33 ohms on Q105. Q102,103,106,107 Transistors, K-610 C945p - appear bad, measured resistance between E & C, don't think there should be any - B to C was able to measure both directions. Q101, 108, 109 Mosfets 2N7000 G08 - not sure how to test these - they are marked S-G-D - tried to energize not sure I have the correct type of meter - just reading resistance seemed they were all high. Anyway, with a little help on what to order I would replace the transistors and mosfets. ThanksComment
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Re: Hp L1906 Monitor
Finally had time to sit down and check things out. Items in red, P607 BD6F2P at Q104 & Q105 - checked pin 1 to all other pins, the only pin that did not appear open was 1 to 3, 15 ohms on Q105, 33 ohms on Q105. Q102,103,106,107 Transistors, K-610 C945p - appear bad, measured resistance between E & C, don't think there should be any - B to C was able to measure both directions. Q101, 108, 109 Mosfets 2N7000 G08 - not sure how to test these - they are marked S-G-D - tried to energize not sure I have the correct type of meter - just reading resistance seemed they were all high. Anyway, with a little help on what to order I would replace the transistors and mosfets. ThanksWhatever I do, I consider it a success, if in the end I am breathing, seeing, feeling and hearing!Comment
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Re: Hp L1906 Monitor
Thanks - how about the transistors and MOSFET's. Where's the best place to try to learn/translate the numbers/markings? I pulled up the data sheet on C945p transistor but don't totally understand all the terms to then order the correct thing from Digi-Key - but did give it a shot. ThanksComment
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Re: Hp L1906 Monitor
Use findchips.com--- begin sig file ---
If you are new to this forum, we can help a lot more if you please post clear focused pictures (max resolution 2000x2000 and 2MB) of your boards using the manage attachments button so they are hosted here. Information and picture clarity compositions should look like this post.
We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings.
Please do not post inline and offsite as they slow down the loading of pages.
--- end sig file ---Comment
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Re: Hp L1906 Monitor
Thank you, that does help. The only source for the transistor lists them at $9.00 each - can they really be that much?Comment
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Re: Hp L1906 Monitor
i love ebay sometimes..
http://cgi.ebay.com/220422965955
http://desc.shop.ebay.com/i.html?_nk...LH_TitleDesc=1Comment
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Re: Hp L1906 Monitor
You can purchase the C945 from a number of sources. You can order 1 or 2 from the large parts houses for approx 10 cents each and pay $8.00 S/H or go to ebay and purchase a 100 for $3.00 w/ free ship!
http://shop.ebay.com/?_from=R40&_trksid=m570&_nkw=c945Comment
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