Hi McFischer,
I have a vp171b, like the one you describe in a recent post with the slow and hard to start power supply problem.
Can you tell me what the solution was to that problem?
Thanks
mcfischer
Member
Last Activity: 11-16-2021, 03:22 PM
Joined: 12-11-2008
Location: Kansas City
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Re: ViewSonic VP171b takes a long time to turn on
I have acquired a dozen or so of these "slow start-up" VP171b monitors.
I concur that the problem is in the 12V power supply. Some of them use the common 3842 IC used for years in smps designs. Pin 7 is power in. Starts up when voltage reaches about 16v, depending on the version (some low voltage versions lower startup volts).
Commonly the smps uses a "trickle" resistor from primary B+ (160+V) for startup, and a "run" winding from the smps secondary to keep running.
No "trickle"... -
Re: acer AL2416w HELP
I have fixed some of these by replacing 8-10 caps and the shorted FETs on the inverter board. There are two groups of 4 100uF 35v elect. glued together that need replacing. You can check the surface mount FETs with an ohmmeter for shorts. There are two other caps on the board that are usually high esr.
MikeLeave a comment:
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Re: Gateway FPD2485W 24" LCD Fuse Blown, caps the cause?
I just fixed one an hour ago. Complaint was "Flashes and dies". Powered up and lit up the bulbs for several minutes until ... (quiet snap) then dead.
Fuse open. ohmmeter showed a short across the big cap. It was the smps FET had shorted. The BIG cap esr was over 100 ohms. Replaced big cap, FET and Fuse and all is good.
MikeLeave a comment:
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Re: Samsung 930b monitor (need help with problem)
The fuse is the brown plastic cylinder next to the AC jack.
MikeLeave a comment:
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Re: Daewoo L700C 17” LCD – power supply problem?
Oops. My last post recommended replaciing the big cap if LESS that 2 or 3 ohms. That is backwards. Lower esr is good. I fixed a Samsung yesterday that had those symptoms (noise when high current but worked) ESR of the big cap was higher than 100 ohms. I use a currect monitor and saw an increase in current draw with the noise.
MikeLeave a comment:
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Re: Daewoo L700C 17” LCD – power supply problem?
I recommend checking the ESR of the big cap (AC input). If lower than 2 or 3 ohms replace it or just replace it.
MikeLeave a comment:
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Re: Dell 1703fps dark screen but power lt steady
The inverter board you have is made by Lien Chang and is notorious for frying a transformer, disabling half the lamps. You can often see the black soot at the inside edge of the transformer, between the lamp sockets. They use a hard black "potting" material to insulate the secondary voltage that makes removal difficult unless you have a dremel grinder.
I have not fould a source for the transformer. I do rob them from other Lien Chang inverters like one used in some 15" HP 1530s.
MikeLeave a comment:
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Re: Hyundai B91a (backlight Problem )
I think you should sub the backlights and try the heat test. Your symptoms steer me toward suspecting weak bulbs or bad connections to the bulbs. Reminds me of the Dell 19" model that would work for a long time then shut off the backlights. Cycle power and it works again for a while, sometimes for a shorter time until shut down. All cured by replacing backlights.
MikeLeave a comment:
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Re: Hyundai L90D+ inverter mosfet problem
I got 7 of the L91D in with one mosfet shorted. APM9932. SMD caps are all OK. judging fromm ESR readings I guess they are 1 uF or close.
Not easy to find these FETs. However, I just finished a batch of 40 IBM 9417-hb7 made by Samsung with fried mosfets and some shorted zeners.
They use SI4532DY (mouser 512-SI4532DY; $0.37 in hundred) Current rating is lower than the APM9932 but they do the same job. Customer was in a hurry so I used these in the Hyundai's. Temps are normal, all 7 have been in burn-in all day. Unless one fails...Leave a comment:
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Re: Gateway FPD1530 works for a second then dark
Bill,
Yes the two electrolytics. I replace them with 2.2 uF just to feel better. Been doing this stuff a long time and I think it may help in the long run.
I have fixed more than 50 this past 2 years, same caps....
MikeLeave a comment:
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Re: Gateway FPD1530 works for a second then dark
I fixed many of these by replacing the 2 1Uf caps at the top edge of the board (between the bulb sockets)
MikeLeave a comment:
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Re: Gateway fpd1530--Did I kill it?
I have fixed many of these. Always the same fix.
Replace the two 1Uf caps on the edge of the power board, between the lamp plugs. I use 2.2 Uf and after over a year no recalls on 50+ units.
Monitor MikeLeave a comment:
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