Re: 12V input to 19V@3A output converter
I know about those but I was more interested in building one myself. Found
a boost controller from Linear Technologies (LTC3786) that supports an
input voltage of 4.5-24V and output voltages up to 60V. There is a nice
example of a 12-14V input to a 24V@3A design with some minor adjustment
that should do what I need it to do.
Aruba...
Aruba
Senior Member
Last Activity: 10-27-2021, 04:40 PM
Joined: 05-25-2010
Location: North Andover, MA. USA
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Re: Viewsonic 20" VG2030wm
Thanks for the suggestion. I will check it out. I have already ordered
similar Vishay parts. Hopefully they will be arriving next week and I will give
an update when I have these FETs and the new caps installed.
Aruba...Leave a comment:
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Re: Viewsonic 20" VG2030wm
Thank you for the different part numbers. I checked with my usual sources and
none of them carry these parts. Do you know of a source where I can order
these parts ? All the electrolytic caps on the power supply are indeed HERMEI.
I will make sure to replace all of them before I power this unit back on.
Wah...Leave a comment:
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Viewsonic 20" VG2030wm
Found this LCD monitor in the hallway at work with a post-it note that
says "Dead". Took it into the lab and attached AC power and only the blue
light came on on the on/off button and nothing else. Opened it up and found
no visible bulging caps but did find two popped FET ICs. These should be the
inverter driver FETs with part# STM8306 printed on them. There are a total
of four of these ICs and only two are visibly damaged. The other undamaged
two although measuring ok may have seen adverse effects that probably
needs to be replaced... -
12V input to 19V@3A output converter
Would like to build a 12V to 19V@3A converter. Basically it takes a car
11-14V as input and provide a stable 19 +/-0.5V at 3A max to provide
power for the laptop/notebook. Any such boost converter circuit available ?
Aruba -
Re: Samsung Syncmaster 245BW
Isn't there an clear insulator sheet that goes in between the board and
the shield cover ? I think that is shown on the left hand side of your picture.
Do you see any arcing marks on the shield in the area you added the electrical tape ?
In any case the electrical tape seems to be providing you the needed
insulation and should work for the long haul but if you were curious and want
to know exactly where the arcing spot is we will need to dig into it a little
more.Leave a comment:
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Re: Samsung Syncmaster 245B
Yes the "big" 82uF, 450V cap measured 0 uF and caused the typical 380VDC bulk voltage to fluctuate and causing the flicker. It has been awhile since that
LCD monitor was fixed and when I do see the owner I ask him if it it still good
and he tells me it is still working perfect.Leave a comment:
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Re: Samsung Syncmaster 245BW
If you getting a steady 390V on pin 23 of the F9222L controller it means you PFC is
working correctly. The problem is then with the F9222L controller which is used to
develop the 24V output. The 5.3V output is developed from the 24V. If you don't have
the 24V output you will not get a 5.3V output.
A good place to start is to measure all the transistors, diodes and resistors connected
nearby the F9222L controller. Make sure they are not shorted or open and the resistors
are still of the correct value as marked on...Leave a comment:
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Re: Samsung Syncmaster 245BW
QM801 is specified as a KST2907 general purpose PNP SOT23 transistor.
Part is available at Mouser.
Aruba...Leave a comment:
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Re: Samsung 245 BN44-00195A Supply
Yes extreme caution should be taken whenever you are working on the
primary (HOT) side of the circuit. The beauty of the power factor correction circuitry is that the bulk cap on the typical 400VDC bus will always be around
400VDC when working correctly regardless of the input voltage which may be
at 100VAC (Japan), 120VAC (North America), 208VAC (North America) or
230-240VAC rest of the world. This is such that the current drawn of the
equipment is more sinusoidal in sync with the voltage...Leave a comment:
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Re: Samsung 245 BN44-00195A Supply
This monitor has a power factor correction circuitry on the front end and therefor you should see 380-390VDC on the 82uF, 450V cap. When you measured the voltage across
the 82uF cap and it was at 160V I am assuming you did this with a DVM. If the 82uF is
very low in capacitance the voltage might be swinging from zero to 380V and giving you
an RMS voltage of 160V on the DVM. If you have a scope you might want to see what
the "real" voltage waveform is on this cap. I suspect it might be swinging from zero to 380V...Leave a comment:
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Re: Samsung Syncmaster 245BW
Hi Bill,
I don't have an ESR meter or I could try this but could it be by default that
when the meter reads 0uF the meter displays 0 ohms ?
What does the meter read for ESR when one measures a 2 inch 20GA wire
(basically a short) ?...Leave a comment:
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Re: Samsung Syncmaster 245BW
Yes the 270uF cap I replaced the 82uF cap with was a little too big. It
was however only for me to confirm that the problem was with the bulk
capacitor. When I assembled it back together I actually used a 100uF, 450V
cap even though it was slightly taller it still fitted perfectly in the space.
Hope this cap replacement will fix your monitor as well. If not you can post
your findings and we will see if we can help.
I am using the 245BW monitor now to type this message. I have asked my
...Leave a comment:
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Re: Samsung Syncmaster 245BW
It was not as clear cut. The 5V was rock solid and the 24V was only fluctuating when the load was above 2A or so. With these symptoms
and not having seen a large bulk cap reduce its capacitance by more than 50% ever before it was not an obvious place to look. It was only through
persistance that the 24V was fixed and secondly that is is a nice big 24"
monitor. I couldn't see this monitor sitting in a corner collecting dust.
Oh I also liked your saying, so appropriate !...Leave a comment:
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Re: HP w20 LCD Display Inverter, running out of options.
I am confused. On your previous post you mention that the "yellow" 3.05V
turns to 0.58V when the monitor shuts off. On this post you say the 3.05V
goes to 0.61V and yet the monitor turns on. Am I reading this right ?...Leave a comment:
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Re: HP w20 LCD Display Inverter, running out of options.
A few questions:
- When you did the heating and freezing you say "without any success",
does that mean it still takes 1 hour before the monitor shuts down ?
- Does it take longer to shut down if the brightness is set at ~10% vs 90% ?
- Once it is shut down, can you turn the AC power off then back on immediately and
does it take yet another hour before it will shut down again ?
- Once it is shut down, does freeze spraying make it recover ?
- Are the main voltages...Leave a comment:
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Re: HP w20 LCD Display Inverter, running out of options.
Do you have access to a can of freeze (cold) spray ? This could narrow the
component or the area that is heating up and causing the shutdown. On the other
hand a heat gun with a narrow exhaust vent can help narrow the area of what is
causing the shutdown much faster than the 1 hour you are waiting now until it
happens. A hair dryer could help also if you do not have a heat gun. Once you find
the area or component you can alternate using the freeze spray can and the heat
gun and...Leave a comment:
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Re: Samsung Syncmaster 245BW
We are back ! Was busy at work so this monitor had to wait. For those that have not given up I have good news to report. If your 245B monitor problem is not related to QM802 or RB805 and you have a flickering monitor then the following might help you.
I did not have the 82uF, 450V bulk cap or sometimes referred to as the hold-up cap that allows a line dropout of maybe a 1/2 cycle to go by without
you noticing there was a line dropout but decided to remove it today and
measure it. I do not have an ESR meter but do...Leave a comment:
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Re: Samsung Syncmaster 245BW
Got some new TDA4863 - PFC controllers in and replacement of it did not fix
the problem. The flickering is still present and while measuring the power
factor it is only around 0.65 vs 0.97 that I was able to measure from a
co-worker's similar monitor. He is not willing to let me take it apart and take
measurements on the power supply board though
. I am kind of stuck
now as what to do next. I will recheck all the components around this
controller one more time and see if I may...Leave a comment:
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Re: Acer AL2423W: Recapped, Still Dead!
These zener diodes on the gate of the FET is used for protection. They are
typically "optional". I have seen schematics where these diodes are marked as
"NC" meaning no connection. The board is layed out with place setting(s) for
these diodes but they can opt out of not having to put them on based on
accelerated life testing, simulated lightning, overload and repeated on/off
cycle testing. But if they had failures during these test they can add these
diodes...Leave a comment:
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