Samsung HPS4253 no power, PSPF391A01A / BN96-03252A power supply repair

Repair service for Samsung PSPF391A01A / BN96-03252A power supply which is used in the following Samsung Models,

     HPR4272X/XAA, HPS4233X/XAA, HPS4233X/XAC SD03, HPS4233X/XAC SG04, HPS4233X/XAC SD01, HPS4233X/XAC SG02, HPS4253X/XAA, HPS4253X/XAC SD01, HPS4253X/XAC 0001, HPS4253X/XAC SD03, HPS4253X/XAC SG02, HPS4253X/XAC SG04, HPS4273X/XAA and SPS4243X/XAA

Typical failure symptoms that indicate power supply failure: No power. Totally dead, no standby LED and does not respond to buttons being pressed. TV shuts down immediately after being turned on. TV makes a clicking sound.

If you are interested in having a PSPF391A01A / BN96-03252A power supply or any other power supply repaired professionally contact johnpreher@gmail.com

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Samsung HPT5044 (HPT5044X/XAA) BN44-00162A power supply repaired.

To learn how I repaired this power supply email johnpreher@gmail.com

HPT4254X/XAA, BN44-00162A Professional Repair:
If you are interested in having a BN44-00161A, BN44-00162A or any other power supply repaired professionally visit http://www.preherservices.com.

Make Your Own Ring Tester

In this post I will share with you all the info you will need to make a homemade ring tester also called a FBT/LOPT tester, note FBT= Fly Back Transformer, LOPT= Line Output Transformer.

Although originally designed to test flyback transformers this tool is used more often today for checking the primary winding of SMPS transformers for shorted windings and also the primary and secondary windings of high voltage transformers found in inverter circuits along with other high Q inductive components.

Click here for the assembly manual for the original dick smith ring tester which is no longer in production. This manual includes a schematic and a parts list.

Below are some pictures of the beautiful ring tester my good friend Behzad made using the schematic and parts list from the included assembly manual.

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Gateway 2100 repaired

I felt it was time to post another case history.

Gateway 2100 LCD monitor, the monitor would turn on screen would flicker and then go black. After opening the monitor I found 1 capacitor, 47uF @16V with an ESR of 10 ohms(obviously bad) in the secondary side of the SMPS section of the SMPS/Inverter board. Looking at the inverter section I noticed two puffed and vented electrolytic capacitors both 220uF @16V, locations C301 and C302 that were obviously bad as well. Sorry but I did not record the location of the 47uF capacitor, but you can see where all the capacitors were located in the photos. I also noticed some darkened spots on the component side of the PCB, on the other side, the solder side of the PCB you could see that where the dark spots were is where the inverter circuit MOSFETs were located, U301, U302, U304 and U305.After testing the MOSFETs for shorts between gate to drain and gate to source to my surprise they tested good, but they did have major solder connection problems, the solder on their connections had completely broken down from heat. I re-soldered all the connections and replaced all the bad electrolytic capacitors and checked for any other problems with the monitor. After putting the monitor back together hooking up signal and turning it on, it worked like new.









If you are wondering why the transistors are identified with a U instead of a Q, as normally transistors are labeled with a Q and ICs are labeled with a U, well this is the case on some PCBs the designers will label transistor locations with U instead of Q and instead of labeling ICs as U they will just print IC.

Mail in repair service:
We offer mail in repair service on LCD monitors. We do the repair on the PSU/inverter board from the monitor in this post for $75.00 plus return shipping and handling. Click here to see our mail in repair service page for more information.

VIZIO L32 HDTV, No Backlight, Repaired

A VIZIO L32 HDTV came into the shop that would power on, the standby/power LED would go from amber to green and TV had audio but no picture. The back lights were not coming on, not even briefly. I opened the TV and powered it on. Next I checked all my secondary voltages on the SMPS to see if they were all present and within tolerance. Immediately it was apparent one of my voltages was missing, and it was the voltage to the inverter board. I disconnected the cable that connects the SMPS board to the inverter board to see if the voltage returned with the inverter board disconnected, so that I could verify it was the SMPS and not the inverter board that was failing. After disconnecting the cable and turning the TV back on the secondary output was still measuring 0V. I removed the power supply and checked the corresponding components for that output on the SMPS. I found the .027uF 630V MKP "bootstrap" capacitor location C9 was swollen and obviously bad. I check the rest of the surrounding components, for instance secondary diodes and filter capacitors and the Power MOSFETs on the primary side that are connected to the bootstrap capacitor. Everything was fine so I replaced the MKP capacitor with a .022uF 630V MKP from another board I had and put the TV back together. Upon turning the TV on it powered up the backlights came on and the TV is working great.

Bootstrap Capacitor Defined:

A N-MOSFET/IGBT needs a significantly positive charge (VGS > Vth) applied to the gate in order to turn on. Using only N-channel MOSFET/IGBT devices is a common cost reduction method due largely to die size reduction (there are other benefits as well). However, using nMOS devices means that a voltage higher than the power rail supply (V+) is needed in order to saturate the transistor and thus avoid significant heat loss.

A bootstrap capacitor is connected from the supply rail (V+) to the output voltage. If the capacitor is polarized then the orientation of the capacitor is as follows: Anode(marked with ‘+’)→(V+) and Cathode (marked with ‘-’)→Output. In other words, the capacitor should be between the output (source of an N-MOSFET) and (V+). Usually the source terminal of the N-MOSFET is connected to the cathode of a recirculation diode allowing for efficient management of stored energy in the typically inductive load (See Flyback diode). Due to the charge storage characteristics of a capacitor, the bootstrap voltage will rise above (V+) providing the needed gate drive voltage.

Hope you enjoyed this repair tip if you have any questions you can always email me john@preher-tech.com. Have a great day.

Professional Repair: If you are interested in having your power supply board repaired professionally then you may be interested in our mail in repair services. We can do the repair on this particular power supply for $150 plus the cost of return shipping and handling. Click here to see our mail in repair service page. You can also email contactus@preher-tech.com for more information.

Troubleshooting and Repairing LCD TVs. This 195 page easy to follow repair guide is only $20 dollars. Read more by clicking this link, LCD TV Repair Guide.

Samsung Syncmaster 906BW, LS19MEWSFY/XAA, Repaired

Samsung Syncmaster 906BW, LS19MEWSFY/XAA LCD monitor came into the shop today with no picture(really it was that the back lights were not lighting). Upon opening the monitor and removing the SMPS/Inverter PCB, I noticed 2 puffed and vented electrolytic capacitors right away. I checked all the rest of the electrolytic capacitors in the SMPS with my ESR meter to make sure no others were faulty and they all were within tolerance for both ESR and capacitance. I scanned the SMPS for bad solder connections and found none. Next I removed the 2 1000uF @10V electrolytic capacitors that were puffed at locations C109 and C110 and replaced them with 2 1000uF @25V electrolytic capacitors with a 125 degree Celsius temperature rating(not necessary to go up in temp. and voltage rating this much or at all but don't use anything less than the originals). After reassembling the monitor and turning the monitor on, it worked like new.

More information at preherservices.com

Samsung HPT4254 (HPT4254X/XAA) BN44-00161A Power Supply Repaired.

To learn how I repaired this power supply email johnpreher@gmail.com

HPT4254X/XAA, BN44-00161A Professional Repair:
If you are interested in having a BN44-00161A, BN44-00162A or any other power supply repaired visit preherservices.com

SMPS common failures

Most Common SMPS Problems,The following probably account for 95% or more of the common SMPS ailments:

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Supply dead, fuse blown - shorted switchmode power transistor and other semiconductors, open fusable resistors, other bad parts. Note: actual cause of failure may be power surge/brownout/lightning strikes, random failure, or primary side electrolytic capacitor(s) with greatly reduced capacity or entirely open - test them before powering up the repaired unit.
Supply dead, fuse not blown - bad startup circuit (open startup resistors), open fusable resistors (due to shorted semiconductors), bad controller components.
One or more outputs out of tolerance or with excessive ripple at the line frequency (50/60 Hz) or twice the line frequency (100/120 Hz) - dried up main filter capacitor(s) on rectified AC input.
One or more outputs out of tolerance or with excessive ripple at the switching frequency (10s of kHz typical) - dried up or leaky filter capacitors on affected outputs.
Audible whine with low voltage on one or more outputs - shorted semiconductors, faulty regulator circuitry resulting in overvoltage crowbar kicking in, faulty overvoltage sensing circuit or SCR, faulty controller.
Periodic power cycling, tweet-tweet, flub-flub, blinking power light - shorted semiconductors, faulty over voltage or over current sensing components, bad controller.
In all cases, bad solder connections are a possibility as well since there are usually large components in these supplies and soldering to their pins may not always be perfect. An excessive load can also result in most of these symptoms or may be the original cause of the failure. And don't overlook the trivial: a line voltage select switch in the wrong position or between positions (possibly by accident when moving the supply, particularly with PCs), or damaged.

More information at preherservices.com