HP1940 backlight
I have an HP1940 19" LCD monitor, and the backlight isn't working. I'm not sure if it's the bulb or driver. Is there a safe way to test? I have a multimeter and know how to use it. If the parts are inexpensive enough, I might repair it.
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Re: HP1940 backlight
You'll have to pull off the cover and post some clear focused photos of the power board using the "manage attachments" button. -
Re: HP1940 backlight
OK I'll do that when I get a chance. Can you tell if the bulb is burned out by looking at it or testing continuity/impedance/voltage across it?Comment
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Re: HP1940 backlight
If this is a Benq style board, it is likely one or more of the following.
1) inverter transformer pins MUST be resoldered
2) picofuse could be blown (open)
3) c5707 transistors are shorted
4) fu9024 fets are shorted
Take it apart and post pictures using the manage attachments functions and do not post inline or offsite.--- begin sig file ---
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Re: HP1940 backlight
You MAY be able to tell if you strip them out,but that happens, only if you have confirmed one or more is causing the problem, either because the lamp has failed ot the wiring has burnt out,normally on one of the return wires.
Your multimeter is of no use to test these, and you really need a test ccfl to determine if they are causing the fault.Comment
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Re: HP1940 backlight
Hey guys. I found what appear to be scorched transistors on the BenQ power supply board. (see attachments). Does anybody know how much these cost, and a good supplier? (preferably in Canada).Attached FilesComment
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Re: HP1940 backlight
Good luck finding parts in Canada. I ordered mine off ebay.ca. Just search for c5707 kit. It should be around $4 to $6 and you will likely get
4 - c5707s
2 - fu9024s
1 - 3A 125V picofuse
edit: The damage looks pretty bad. It might be beyond repair, but the cost is relatively low and it is worth trying to save a 19 inch monitor?Last edited by retiredcaps; 05-09-2011, 05:24 PM.--- begin sig file ---
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Re: HP1940 backlight
You probably won't find these in Canada, and if you do, they'll be marked up 800%
Ebay is your best bet.
Test the ones that aren't charred, they could be bad too.36 Monitors, 3 TVs, 4 Laptops, 1 motherboard, 1 Printer, 1 iMac, 2 hard drive docks and one IP Phone repaired so far....Comment
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Re: HP1940 backlight
On closer inspection with a bright light the damaged components are:
C5707 (x2)
D10PF (attached)
I found this repair kit on eBay for $5:
http://cgi.ebay.com/ws/eBayISAPI.dll...m=220778537253
(USA is much better than waiting a month for it to come from China!)
The board in the ad doesn't look like mine. Also, they provide a FU9024N and a 3A fuse. Mine is 5A (see attached). Is it the right kit?
Can any of these components be damaged by a soldering iron? What are the test values for the transistors?Attached FilesComment
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Re: HP1940 backlight
The FU9024N will work in place of the D10PF, I've done it, and lived to tell about it.
If you don't know how to test, or don't have the equipment, it might be just as easy to replace them all, they're cheap enough.
USA might be just as slow as China, lately shipments via Canada Post have been very slow, but it does vary, so you might get lucky.
The 5A fuse might explain the crispyness of the transistors. Hard to say what the original should have been, 5 seems high, but might be original. On the BenQ models I've done that have a similar circuit, it's always been a 3A.
You generally won't damage them with soldering heat during install, if you're any good at soldering. De-soldering them if you're not good, could damage, but they're already toasty anyway.Last edited by smason; 05-09-2011, 06:18 PM.36 Monitors, 3 TVs, 4 Laptops, 1 motherboard, 1 Printer, 1 iMac, 2 hard drive docks and one IP Phone repaired so far....Comment
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Re: HP1940 backlight
This company will sell you the entire board if you want to pay a little extra.
http://www.lcdrepair.us/Invpowersupply.htmlComment
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Re: HP1940 backlight
Nah, we don't buy boards here, we fix 'em!
That said, their prices look pretty reasonable.
I'm waiting to find a replacement transformer for a Dell monitor on my shelf. They'll sell the whole inverter for $20.00 Tempting, but I don't like the monitor *that* much, plus with shipping to Canada, it definitely won't be worth it.
I know I'll eventually find a donor monitor.36 Monitors, 3 TVs, 4 Laptops, 1 motherboard, 1 Printer, 1 iMac, 2 hard drive docks and one IP Phone repaired so far....Comment
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Re: HP1940 backlight
Just wind your own transformer! hehe J/K. There's monitors all over craigslist. You might even be able to pull a step-up xformer out of some other appliance.
By the way, check out this youtube channel and watch a crazy brit pump kV's and kA's into various devices and objects :P The coconuts are the most entertaining.
http://www.youtube.com/user/PhotonicinductionComment
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Re: HP1940 backlight
Brit, with a capital B please.......Comment
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Re: HP1940 backlight
Blimey!
I got my eBay repair kit today (shipped out May 5th) nicely packaged in a static shielded baggy. (Seller was "coreweave" for those wondering). I marked the connectors so I don't mix them up. I'll begin the repair when I get home from work tonight.
I have a couple of questions for you guys. Some of the traces have lifted away from the PCB. My plan is to just reflow the solder, leave as is, test the monitor, and if needed, add some wire segments and clean away excess rosin with isopropyl alcohol since they could be high-voltage circuits. What would you do?
The transformers look OK, but I should resolder them right? All four?
Thanks.
- JoeAttached FilesComment
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