Question about HP L1955 19" LCD Monitor

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Hp l1955 mosfet traces lift, need diagram

Try to replaced famous, known burned MOSFET, traces lifted off the board, no idea where the leads supposed to go, any one can help,? thanks

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I seriously doubt that HP made that monitor, it came from either a contract house or a major manufacturer. I suspect HP doesn't even have service manuals for that product either.
Maybe, maybe, you can ferret out the true maker via the FCC number which it may or may not have; I've noticed that there are a flood of various consumer and industrial items sold without the once mandatory FCC approval and consequently, no number either.
FCC ID site 
Even if you can find the maker's name, they may consider the content to be proprietary; during my active years of service work, I have been turned down dozens of times when trying to buy service literature.  

Posted on Nov 01, 2008

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Mosfet keeps exploding

Well its clear you have a nasty short somewhere, problem is with no schematics for this set how will you find the problem much less get the correct part?

Might be better to shop for a different board to replace this board with.

Dec 11, 2012 | Samsung HP-T4254 42 in. Plasma Television

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Hp 625 no power on

Test your PSU power supply unit or replace it if your power supply units fan is not working your PSU is faulty WARNING: Before you start troubleshooting remember that you are dealing with electricity that can KILL. - rules

Test all power and data leads that attach to your hard drive IDE,SATA
The leads from your MOTHERBOARD TO YOUR HARD DRIVE make sure they have secure dust free connections and are not faulty. Any bad or faulty power or data lead or connection can cause a computer not boot up.
Motherboard and a Hard Drive any leads between them will fail before your motherboard or your hard drive if its a flat ribbon 40 pin type IDE replace it this will be the first to fail. Make sure your graphics card is securely seated with no dust built up or in the socket if you remove your graphics check the socket to make sure its dust free restart your computer then reinstall it this should activate found new hardware wizard Make sure all leads that are attached to your drives dvd\cd floppy have secure dust free connections and are not faulty or just replace them they could be faulty a computer needs Power and Data to travel through every working device and to continue its cycle and have an end so any faulty leads will end up with a computer error even something as small as a faulty power lead or fan lead can cause you problems computers need all of the data and electrical current to travel through every working device and to have an end to be able work properly Make sure ram modules and cmos batteries have dust free secure seatings and cmos battery has charge some motherboards cmos batteries are soldered in Check you CPU make sure its securely seated and has thermal grease Hope this helps.

Dec 10, 2012 | HP Computers & Internet

1 Answer

I've replaced the mosfet rjh3047 because short-circuited. the new one is gone as well shorted. thing else I can check?

you must have some diagram b) must test some around components like capacitor+diode+resistor+ic+Trafo , that will be in short circuit this will provoke the short in your MOSFET transistor.

God bless you

Oct 15, 2012 | Samsung LJ92-01393A BN96-04594A...

1 Answer

I have dell inspiron n5030. The power adapter light turns off when connected to laptop and hence not charging the laptop.

Bad Power MOSFETs.

Using the HP Pavilion dv6000 and Pavilion dv9000 series Notebook PC's, for an example,

General example of the -> package type, of the Power MOSFET/s used,

The 'legs' (8) on the sides are Leads. This particular style is known as a J-lead.

Using the Fairchild Semiconductor International - Power MOSFET - FDS6679 as an example,

$1.01 USD

Another component that may go bad are the Ceramic Capacitors, and near the Power MOSFET/s.
Looking at the first link, Mayohardware, look down at the second photo. AO4407

To the right of the Yellow circled AO4407 Power MOSFET, is a Ceramic Capacitor. Small rectangular shape with a wide dark band in the middle.

They burn, bubble, and blister just like the Power MOSFET's do.


Oct 08, 2012 | Dell Inspiron N5030

2 Answers

Pioneer MOSFET 50wx4 troubleshooting

MOSFETs are not always easily checked with a DVM, their contact resistance is very high between the gate and drain or source leads, b ut you can get reasonable assesment. When testing, use highest resistance range.

Gate to Source ,Gate to Drain resistance is normally more than 1 meg Ohm, 500,000 ohm is marginal but acceptable. The polarity of test leads will yeild the lowest readings for N channel MOSFET when the positive test lead is attached to Gate. When reversed, readings should be higher.

Source to Drain, Drain to Source should be greater than 1 Meg Ohm either polarity or test leads. Lowest acceptable is 1 Meg Ohm.

Otherwise if you have a transistor tester that will test regular Junction Fets or JFETs, that will work most of the time, but you may have to remove them from the circuit to test them accurately, especially if you recieve no indication of condition in circuit.

Normal failure mode of MOSFETs is to burn open.

If the amp went silent, test the caps, replace off the electrolytics and tantalums in the finals/output stage.

If one chanel failed, check the preamp and drivers. If the speaker voice coils burned out- replace the output capacitors.

You may need to power up the amp- do not leave them unloaded, if nothing else use a wirewound cement resistor of 8 to 16 ohms. Then you can start with a pair of headphones, attach test leads to the contacts so you can trace the sound path in the amplifier to listen for distorted signals- conventional Class A, B, AB and C audio amplifier designs have locations where you are hearing part of the sound wave, and they will sound muffled and indistinct, the key is if that distorted wave continues through the amp, and you have the other channel to use as a baseline for compairison.

Feb 12, 2012 | Pioneer Car Audio & Video

1 Answer

I have got tft hp l1908w with powersupply problem. it is not powering on and the main capacitor is not discharging after i replaced mosfet

The SMPS is not triggering and driving the MOSFET and so this makes the +B voltage build up on the main capacitor to HOLD on without drain as there is no switch frequency to drive the MOSFET.
Please try and trace the feedback to the MOSFET, can be the SM transformer, the feedback circuit or also a short on the secondary side.

Jul 12, 2011 | HP L1908W 19" LCD Monitor

1 Answer

HI I have a FSP200-61GT SPI switching power supply with a burned out Mosfet on the high voltage side. There is a (I think)a .5 or 1 watt resistor on both sides of the mosfet. But they test good, my problem...

Please give motr of the devices fixed on same heat sink. Search for SMPS IC like FPS or similar, search their application notes and the datasheet of the nMOS. then you can get idea. without those data Solution is impossible.

Jan 27, 2010 | HP and Compaq Pavilion Replacement 200w...

1 Answer

Mosfet check

1. Switch your multimeter to the Diode test position.
The following steps are for an N-Channel MOSFET.
Hold the Black lead to the MOSFET's source terminal.
2. Touch the GATE terminal momentarily with the Red lead.
3. Then touch the DRAIN terminal with the Red lead without touching the GATE terminal with your fingers.
The multimeter should show a low reading now. (The MOSFET is now ON)
4. With the RED and BLACK leads still connected to the DRAIN and Source terminals of the MOSFET, now touch the GATE terminal with your finger. The Multimeter should immediately show an open cct. (The MOSFET is now OFF)
This is a very simple way to test a MOSFET.

Jan 13, 2010 | Epson >>> IM800 DARK GRAY 733 MHZ CPU...

2 Answers

Power up problem with alesis rs300 (ra300)

you have more than likely damaged some transistors.
the resistors have burned because of excessive current.
there are 2 typesof transistors,bipolar and mosfet
a bipolar transistor has 3 pins.1) base 2)emitter 3)collector.
an NPN is tested with the + meter lead on the base , and a PNP transistor with the - lead on the base.
base to collector should read .5 to .6 v drop in one direction and open in the other with a digital meter on the diode check function.
base to emitter about the same,but slightly higher than the collector.
if base to collector is .5v then base to emitter is .52 or is always higher than the base collector number.
between emitter and collector will read open in both directions.
if there is a short on any lead combination,the transistor is blown.
npn transistors operate on the positive rail power supply,and pnp on the negative rail.
typically a 150 watt amp will run + - 65vdc.
the transistors running on the plus side are npn and on the negative pnp.
most pnp output transistors are green.,but some are black,
so we must go by the numbers on the transistors, eg.A1076 is a pnp,B755 is a pnp and all transistors that have a C or D eg. D424 are NPN transistors. all A and B numbers are PNP and all C and D numbers are NPN.
MOSFET transistors have 3 pins 1)gate 2)drain 3)source
the source goes to power like the collector does. the drain is like the emitter,and the gate switches it on like the base does.
testing a mosfet is a different procedure.
a mosfet with k then a number e.g. k135 is a positive device like npn.
a mosfet with j and a number e.g. J50 is a negative device like pnp.
a mosfet reads open source to drain both directions.
for a positive (k number device) the plus meter lead goes on the source.,the black meter lead on the drain. on the diode test function.
jump a wire from the source to the gate for 1/2 second and remove the jumper while leaving the other two meter leads connected to the source and drain.The mosfet should switch on and the meter should show a short.that means the mosfet switched on.About 5 seconds later,the resistance from drain to source should go open.
for a p channel mosfet,it checks the same,except that the black meter lead goes on the source and gate .
a mosfet will stay switched on longer than the voltage applied to the gate,if it is driving a high impedance device such as a meter.
a bipolar transistor will not stay on when voltage is removed from the base lead.
i hope this has been of some help.

Sep 09, 2009 | Alesis RA-150 Amplifier

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