Saturday, January 30, 2010

Samsung LNT4661F, Repaired

Another repair from Preher-Tech.


Samsung LNT4661F-

Symptom:

Takes a while to come on, when it is on, there are red dots over the video.

Repair:

Replaced three 1000uF @16V electrolytic capacitors in the PSU. Location CS804, CV812, CV813.


Check out the ebook Troubleshooting & Repairing LCD TVs.

Friday, January 29, 2010

Magnavox 37MF321D37, No Power. Repaired

Another LCD TV repair from Preher-Tech.

Magnavox 37MF321D37-

Symptom:

No power.

Repair:

Replace electrolytic capacitors in PSU (likely puffed and vented), two
2200uF @50V and two 1000uF @50V.


Check out the ebook Troubleshooting & Repairing LCD TVs.

Thursday, January 28, 2010

LG RM-30LZ50 LCD TV Repaired

Here is the repair for an LG RM-30LZ50- LCD TV that came into our shop.

Symptom:

Irregular glittering speckles on screen.

Repair:

Remove C857, 220uF @16V electrolytic capacitor on main board
and replace with 470UF @16V electrolytic Capacitor.


Check out the ebook Troubleshooting & Repairing LCD TVs.

Wii Repair



New ebook released on Wii console repair. This is a really nice ebook that guides you through many Wii console repairs that can be completed right in the comfort of your own home. This great guide is only $19.99. Once you order you can download this guide immediately



Read more about this awesome guide by clicking here.

Monday, January 25, 2010

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

HPT4254X/XAA, BN44-00161A Professional Repair:
If you are interested in having a BN44-00161A, BN44-00162A or any other power supply repaired professionally then you may be interested in our mail in repair services. We can do the repair on BN44-00161A and BN44-00162A power supplies for $50 plus the cost of return shipping and handling. Click here to see our mail in repair service page.


HPT4254X/XAA, BN44-00161A Repair Kits:
Repair kits for the BN44-00161A and BN44-00162A power supply available from Preher-Tech.
Click here to visit our parts kits sales page.


Had a service call today for a Samsung HPT4254 (HPT4254X/XAA) Plasma TV. Customer said he went to bed with the TV on and when he woke up the TV was ticking, tick, tick, tick etc... no response when the power button was pushed and he had to unplug it to turn it off. When I arrived I plugged the TV in and it still had the symptom. After opening the TV , I removed the PSU(Power Supply Unit) and discharged the large filter capacitors in the primary side of the PSU and then checked the board for bad/cold solder connections, and checked the ESR of all the electrolytic capacitors on the board, and checked the fuses. All capacitors tested good, found very bad ring cracks on MOSFETs QX801 and QX802 and re-soldered these connections. I found that fuse F803 was open, so I checked the corresponding circuit including MOSFETS QS801 and QS802, both MOSFETs were shorted, one between gate and drain and one between gate and both drain and source. After replacing Both shorted MOSFETs and F803 the TV turned on and functioned normally. Hope this helps some of you that have the same failure with this model TV. MOSFETs QS801 and QS802 were both FQA13N50CF.

Note: See all updates below.



Update: 04/16/2011:

We have seen many more of this model TV with the same failure symptom as described above but with a different cause of failure and this cause of the failure seems to be most common so we are posting it now as we realize a lot of people are looking to fix this TV.

The components we are commonly finding have failed are,

F803 is open.

QX801 and QX802 are shorted or have totally blown.

RX802, RX803, RX832 and RX833 are open or have a seriously increased resistance.

RX804 and RX805 are open or have a seriously increased resistance.

DX803 and DX804 are open or completely blown.


Component values:

F803= 8A 250V Time Delay/Slow Blow 5mm X 20mm

QX801 and QX802= FQPF9N50C

RX802, RX803, RX832 and RX833= 20 ohm

RX804 and RX805= 10k ohm

DX803 and DX804= 1SS184T5LFT(this is the part we use for replacement)



Picture showing replaced SMD components on the bottom of the PSU.


HPT4254X/XAA, BN44-00161A Professional Repair:
If you are interested in having a BN44-00161A, BN44-00162A or any other power supply repaired professionally then you may be interested in our mail in repair services. We can do the repair on BN44-00161A and BN44-00162A power supplies for $50 plus the cost of return shipping and handling. Click here to see our mail in repair service page.


HPT4254X/XAA, BN44-00161A Repair Kits:
Repair kits for the BN44-00161A and BN44-00162A power supply available from Preher-Tech.
Click here to visit our parts kits sales page.



Update #2 05/09/11:

We have done many more repairs on BN44-00161A and BN44-00162A power supplies since the last update and have found another failure that happens on a small percentage of them.

Components that may have failed,

QS803, QS804, QS805 and QS806 one or more shorted(check for open junctions as well)

DS823 shorted(may be open as well) check between pin 1 and 3

RS859 may be open or have a seriously increased resistance

U804, if many of the components listed above are bad then you should also replace the Resonant Mode Controller IC



Component values:
QS803 and QS804= NPN 20V 2A SMD BJT(marking ZG)

QS805 and QS806= PNP 20V 2A SMD BJT(marking ZH)

D823= 18V 0.35W SMD zener diode(marking 8Y)

RS859= 4.7 ohm SMD resistor

U804= MC33067P power controller IC




Locations for both of the controller/sub PCBs




Location of power IC



Location of QS803, QS804, QS805, QS806, DS823 and RS859


HPT4254X/XAA, BN44-00161A Professional Repair:
If you are interested in having a BN44-00161A, BN44-00162A or any other power supply repaired professionally then you may be interested in our mail in repair services. We can do the repair on BN44-00161A and BN44-00162A power supplies for $50 plus the cost of return shipping and handling. Click here to see our mail in repair service page.


HPT4254X/XAA, BN44-00161A Repair Kits:
Repair kits for the BN44-00161A and BN44-00162A power supply available from Preher-Tech.
Click here to visit our parts kits sales page.



Don't forget to visit http://www.preher-tech.com and remember if you ever have any electronics related
questions you can always email contactus@preher-tech.com for support.


Friday, January 22, 2010

LCD TV Repair Guide

Well it took a long time, but I finally finished my guide on LCD TV repair. It's titled, "Troubleshooting & Repairing LCD TVs", and you can check it out at our website. This is a 195 page ebook download in PDF format. Check it out today by clicking here or on the photo below.




Sunday, January 17, 2010

PIC Microcontrollers

I personally am studying PIC programming, and really enjoying it. I think at some point in your electronics carreer or hobbie, if you really love electronics and experimenting with electronics you will want to start programming microcontrollers.


Microchip’s PIC microcontrollers are popular with developers due to their low cost, wide availability, large user base, extensive collection of application notes, availability of low cost or free development tools, and serial programming (and re-programming with flash memory) capability. Microchip has over 550 PIC MCUs in its portfolio.




Read more about 8-bit PIC Microcontrollers. Click here.

Friday, January 1, 2010

Happy New Year 2010.

Preher-Tech wants to wish all our blog readers, twitter followers, all that visit our website daily, all our local customers and anyone else that's helps to support our business. Hope this is a great year for all of us in the electronics repair and design business. Looking forward to a great new year.