Thanks to all the helpful posts about blank monitor problems. I have dual 1955 monitors, one died & was replaced in warranty. The 2nd (original) just died (a bit over 3 yrs old). Fuse PF801 blew (BEL MS 5). Q805 (8-pin MOSFET on bottom side) Si4431 CDY was toasted, burns under it and 2 traces burnt & lifted off of PCB. I cleaned the carbon burned spot under Q805, added some tiny Kapton tape pieces (for insurance) and replaced the 4431. ( the "lifted" traces were still useable). Found one shorted C5707 (Q809) and replaced it (and the good one near it) with 2SC5707 transistors. Re-soldered LOTs of bad joints around the transformers & caps. Put it together. It blinked on momentarily, but still had a problem (blank screen). Searching some more I found a bad transistor Q803 (near the bad Q805) was burned and tested bad. The SOT-23 transistors marked "WO4" are NPN 3904 transistors (MMBT3904 or equivalent)). The ones marked "to6" are PNP 3906 transistors (MMBT3906 or equivalent). I didn't find any other bad ones. Problem solved! Monitor works great! I plan to open up the newer monitor and check the solder joints in it, too.
HP 1955 / BENQ 48.L1A02.A00 repair
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Re: HP 1955 / BENQ 48.L1A02.A00 repair
Originally posted by bobbythThanks to all the helpful posts about blank monitor problems. I have dual 1955 monitors, one died & was replaced in warranty. The 2nd (original) just died (a bit over 3 yrs old). Fuse PF801 blew (BEL MS 5). Q805 (8-pin MOSFET on bottom side) Si4431 CDY was toasted, burns under it and 2 traces burnt & lifted off of PCB. I cleaned the carbon burned spot under Q805, added some tiny Kapton tape pieces (for insurance) and replaced the 4431. ( the "lifted" traces were still useable). Found one shorted C5707 (Q809) and replaced it (and the good one near it) with 2SC5707 transistors. Re-soldered LOTs of bad joints around the transformers & caps. Put it together. It blinked on momentarily, but still had a problem (blank screen). Searching some more I found a bad transistor Q803 (near the bad Q805) was burned and tested bad. The SOT-23 transistors marked "WO4" are NPN 3904 transistors (MMBT3904 or equivalent)). The ones marked "to6" are PNP 3906 transistors (MMBT3906 or equivalent). I didn't find any other bad ones. Problem solved! Monitor works great! I plan to open up the newer monitor and check the solder joints in it, too.
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Re: HP 1955 / BENQ 48.L1A02.A00 repair
Manufacturers of computer components usually don't offer parts just complete replacement when under warranty.
These monitors are going on 6 years old now even if parts were available they aren't anymore.
Besides the new board would be made with the same crappy solder joints and caps as the old one it would just fail again.Elements of the past and the future combining to make something not quite as good as either.Comment
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