Viewsonic VG1930WM no power, repaired

I just finished repairing a Viewsonic VG1930WM that had no power, no standby LED, completely dead. I opened up the monitor and checked the output voltages from the power supply and both were present and stable. I verified that the 5V was still present at the main board. Next I checked the output from the 3.3V and 1.8V linear voltage regulator ICs on the main board and the 3.3V regulator's output was considerably low around 2.2V, the output from the 1.8V regulator was also very low but it gets its input from the 3.3V regulator so it makes sense that the 1.8V regulators voltage was low. I replaced the 3.3V regulator after verifying it was faulty and the monitor was still dead when I plugged it in to check voltages again, the 3.3V regulator's output was now within tolerance so I again checked the output from the 1.8V regulator and it was still low about 1.2V, so I then replaced the 1.8V regulator and when I plugged the monitor in to check the output from the 1.8V regulator I saw the standby light turn on, the voltage output from the 1.8V regulator was now within tolerance and the monitor turned on and functioned flawlessly.

Preher-Tech's mail in repair service:
http://preher-tech.com/mailinrepairservice.aspx

Also don't forget to visit http://www.preher-tech.com/

Viewsonic VX910 no power, repaired

Recently did a repair on a Viewsonic VX910 that had no power, no standby LED, totally dead. Upon opening the monitor I could see that someone had already replaced all the electrolytic capacitors in the output filter circuitry, but for this type of failure I normally don't suspect the filter capacitors anyways. I plugged the monitor in to check for any output voltages from the PSU and I could here a faint chirping coming from the power supply, this is always a good indication of a shorted output diode or faulty components in the feedback circuitry, the power supply is continually trying to start up and then shutting down,over and over. As I suspected there was no output from the power supply. I pulled the power supply and the first thing I checked was the dual schotttky diode D660 and one of the diodes in the dual package was shorted. The original diode was a MBR10100CT dual schottky diode, I replaced it with a B20100G dual schottky diode. After replacing the dual diode the monitor powered on and worked once again.







Preher-Tech's mail in repair service:
http://preher-tech.com/mailinrepairservice.aspx

Also don't forget to visit http://www.preher-tech.com/

Philips 37MF321D/37, 37MF331D/37, 715T2056-1 Power Supply Repair

We have been receiving quite a few 715T2056-1 power supplies for repair from Philips 37MF321D/37 and 37MF331D/37 LCD TVs. The failure symptom is typically that the green standby/power indicator led blinks constantly and the TV will not turn on. The most common reason this particular power suppy fails is the 2200uF 25V capacitor at location 2074 has puffed and vented or has a significantly high ESR, some of the other electrolytic filter capacitors on the secondary side of the power supply may have a high ESR as well. The 9.1V 0.5W zener diode(BZX79C9V1 is used for replacement) at location 6079 is commonly shorted, but may also be open as well. The SMD 2.2 ohm 0.125W resistor at location 3045 has opened and is usually burned often damaging the copper trace on the bottom of the PCB. Parts are available from http://www.mouser.com/. If you have any questions regarding this repair or any other electronics related questions please feel free to email me john@preher-tech.com.











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 $50 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.


Remember to visit http://www.preher-tech.com/

HPT4234, HPT4254,HPT4264, No power, Clicking, Repaired

If you have a Samsung HPT4234, HPT4254 or HPT4264 that does not turn on and only clicks or intermittently shuts down and starts clicking and you are looking for information on how to repair the power supply, see our post on how to repair the HPT4254 power supply which also applies to the HPT4234 and HPT4264 power supplies by clicking here.

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 $50 plus the cost of return shipping and handling. Click here to see our mail in repair service page.

Take care and remember to visit http://www.preher-tech.com/

Samsung HPT5044 (HPT5044X/XAA) no power, clicking, repaired.

Samsung HPT5044 (HPT5044X/XAA) no power, clicking, repaired.

This repair was basically a very similar repair to one we often do on the HPT4244 power supplies, but we wanted to give this one it's own post so that people searching for info on the HPT5044 with the failure of no power only clicking when attempting to turn the TV on or also intermittent power and clicking, would be able to easily find this info when searching online. The HPT4244 power supplies that we have been receiving for repair come in with an open fuse at location F803, shorted MOSFETs at locations QS801 and QS802 and open SMD dual package diodes at locations DS801 and DS802. QS801 and QS802 are both AV218N50 MOSFETs, but we substitute with FDA18N50 MOSFETs. F803 is an 8A 250V time delay/slow blow fuse. DS801 and DS802 are both 1SS184T5LFT, UFR dual package common cathode SMD diodes. All parts are available from http://www.mouser.com/.








Click here to read the repair info on the power supply from the HPT4254 which is extremely similar. There is some good info in this post including other components you will want to test if MOSFETs QS801 and QS802 are not shored or F803 is not open as these boards have multiple failures that can happen.


Professional Repair:
If you are interested in having this 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 $50 plus the cost of return shipping and handling. Click here to see our mail in repair service page.


Remember to visit http://www.preher-tech.com/.

Testing HV transformers in LCD TV inverter circuits

This article is from the Preher-Tech May 2011 newsletter. In this article I show you how easy it is to test LCD TV inverter transformers.

Click here to download the article "Testing HV Transformers in LCD TVs"

Also if you are interested in receiving articles like this sent to your inbox each month the join the Preher-tech newsletter by clicking here.

Don't forger to visit http://www.preher-tech.com/

The BLUE Ring Tester

Preher-Tech is now selling the BLUE ring tester fully assembled by us and in kit form as well.

Click here to visit our sales page and get more info.

The BLUE ESR Meter

Preher-Tech is now selling the BLUE ESR Meter fully assembled by us and in kit form as well.

Click here to visit our sales page and get more info.

Sharp Aquos LC32D43U no power

Here is an article from this month's newsletter about a repair we did on a Sharp Aquos LC32D43U that had no power or standby light, totally dead. Click here to download the article "Sharp Aquos LC32D43U No Power"


Professional Repair:
If you are interested in having this 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 $50 plus the cost of return shipping and handling. Click here to see our mail in repair service page.

Repair Kit:
We also have a repair kit for the power supply available for $35.00 which the parts necessary for this repair and includes USPS priority shipping within the contiguous United States. Click here to visit our repair kits page and purchase this kit.


For more repair and other electronics related articles join the Preher-Tech newsletter by clicking here.


Remember to visit http://www.preher-tech.com/

Electronics repair training videos

Click here to visit Randy Fromm's YouTube page and see more of his great videos.

Also click here to see Randy Fromm's Arcade Schools training programs.

Randy Fromm's Arcade School offers a wide range of video training programs, from beginning electronics to advanced microprocessor repair.