Saturday, January 02, 2016

IBM 9512-AB1 TFT Monitor 715A917-1-4 Backlight Inverter Fix

Symptom, no backlight, but the LCD it self is OK.
Inverter board (left) and main board (right).
Inverter board close up.
From my observation, this board will works when hot but not when cold.
A lot of try and error to trace this but finally, found the culprit.
This cap value determine the 5001C PWM controller short circuit protection timing. As mentioned in the 5001C PWM controller datasheet, the timing must be much longer (generally 10 to 15 times) than the converter start-up period or the converter will not start.
Replace with Aluminum caps for testing...
Put it back in...
There you go :-)

Thursday, December 24, 2015

Replacing Haier L32A16 Backlight To LED


Get a white LED strip. 5 meters = USD7

Mount it...

 End result...

Friday, October 16, 2015

Noxxa Multifunction Pressure Cooker - No Power

Just to share how to fix Noxxa Multifunction Pressure Cooker no power issue.
Symptom: The front panel didn't light up. So let's open it.

Start check the simple things first, temperature fuse continuity? OK, any swollen capacitors? nope!

Next, power it up and check is there any output before (AC) and after the bridge (DC)? YES.

Regulator (7805) output? NO! Found it. Input is about 14V but no output

This is the power supply for the front panel circuit board.

 Desolder it out an do a quick test by it an 12v input

No output at all, compare with the new one

Put it back together again, plus a heat sink to the 7805 regulator. This might prevent it from overheating again, I hope so.

Finallly :-)

Friday, October 03, 2014

Samsung SyncMaster 732NW Power Supply Modification

A Samsung SyncMaster 732NW Monitor came in last 3 weeks into my workshop after getting struck by lightning. This is what happen to the power supply board.

A bad capacitor, several diodes shorted, a blown fuse and blown SMPS Power Switch. Luckily the digital board, LCD and back-light still OK.

This is the heart of SMPS, the chopper (PWM) controller with built-in SenseFET by Fairchild.

Too many parts need to be replaced. So here is the shortcut. :-)

From the schematic diagram, we can see that it requires 2 types of power sources, 15VDC and 5.1VDC. Desktop power supply will do the job. It can supply 12VDC and 5VDC. Lower but tested working fine. 5VDC for the digital board and 12VDC for the back-light inverter.

A quick modification using 4-pin peripheral power connector. Several bulky components removed from the heavily damaged primary section.

There you go...

Wednesday, May 21, 2014

Panasonic TH-P42X30K Plasma TV Power Board Fix

This is my own Plasma TV. Symptom, sudden power cut off. Power LED not lit at all when the side power button switched on. According to the service manual [ th_p42x30d_g_k_m_p_s_v_1.pdf ] , this is power board issue.

Trace further and narrow down the search to standby power section. Standby voltage (5V) is totally down.

B159-003 Power Board Block Diagram

This section on the B159-002 power board, component side.

B159-002 Power Board Component Side

This diode fails become short circuit, part of the secondary side of the transformer that feedback to FAN6754 PWM controller pin 2 (FB)

FAN6754 Typical Application schematics, not the actual schematics

It is B3100 diode that should be able to withstand 100V peak and 70V RMS reverse voltage


Replace this FML-G22S, the best I have currently, salvage from old PCB.
It can withstand 200V peak.

Now, I can see the 5V standby voltage. Put everything back together and test.

Will try to find the actual component soon (B3100) for replacement.

Friday, August 16, 2013

Replacing Dell E153FPC 15" LCD Monitor Backlight With LED

My old Dell E153FPC back-light recently failed to light up.Tracing lead me to the bad inverter circuit and broken CCFL back-light.

So replacing with an LED would be a great idea. Refering to Instructables, I'm planning to do the same thing but the LED flex/strip here cost more than a used/refurbished LCD monitor.

A cheap solution is by creating my own LED bar. 3 white LEDs in series with current limiting resistor. Calculated to works with 12VDC.

The CCFL backlights have been removed earlier but I did not snap any image during the process. Please Google for this. Next, test the LED back-light.

Does not look like what you expected? Wait until you turn it on.

Connect it to 12VDC source that can be found on the power supply board. A fuse added just in case. Use a detachable connector for easy troubleshooting later on.

Tadaa! although the light source does not emit its rays uniformly, but for me this is enough since I'm planning to use this monitor just for PC troubleshooting.

Finally, put them back together again. From now on, this monitor is no longer an LCD Monitor but an LED Monitor :-)

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