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EV SxA250 powered cabinet and intermittent high frequency static noise with no input signal applied. The power transformer output is steady and the capacitors test good.

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This kind of noise can be a failing power output transistor, had the very same issue with a Sansui receiver, replaced all four power transistors and noise went away, why all four? I was told that due to small differences in the components from different manufacturer's it was best to replace them as a set, slight diff in bias was the reson given to be specific.

Posted on May 27, 2009

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Posted on Jan 02, 2017

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What's the difference between a surge and a spike in voltage?


A spike is an increase in voltage for 1-2 nanoseconds.
A surge is the increase lasts 3+ nanoseconds.

Feb 05, 2014 | Electronics - Others

Tip

Basic LCD Monitors troubleshooting guides


By Bud Martin
First if you can, try the monitor with other PC first to make sure it is not the PC problem.
Notes: We are dealing with high voltage that can kill you! so if you are not sure what you are doing, please have it fixed by the pro that has proper tools and safety equipment. Try to use GFI outlet and isolation transformer when work around the TV set and DO NOT DEFEAT THE GROUND PIN OF THE OUTLET/POWER CORD.

The monitor will have at least 2 circuits boards, one board will be the logic board where the video cable from PC is attached to, the second board used in most monitors today is the Power supply/backlight inverter board combinations. Some monitors will have separate power supply module and backlight inverter board.
The monitor should be connected to the running PC otherwise it will go into standby mode.
The operations of each board:

1) The Power supply board:
It takes the 120vac 60Hz and converts it to high voltage DC (around 160~170vdc filtered by the 80~150uf 250~450vdc cap) by the bridge rectifiers to be used by the switching power supply circuits that converts this DC voltage into high frequency (around 50~100 KHz) AC for driving the step down transformer. The outputs (usually 2 outputs) of the transformer will be rectified by the diodes to produce the regulated 5vdc for the logic board, and regulated 12~20vdc (12vdc is usually for screen up to 17inch, 16~24vdc for 18~24 inch screen).

The power supply circuits are always on (unless the monitor uses the power switch that actually disconnects the power from the outlet which is rarely used these days) which means that it is running 24/7 using the monitor or not, any spikes and surge will be fed into the monitor power supply.

Common problems:
Blown fuses, bad caps (leaking/bulging tops or bottom seals, please note that bad cap may look normal but it can have high ESR (Equivalent Series Resistance). The DC filter cap should be low ESR type for using in the switching power supply; general purpose electrolytic types will not last very long in switching power supply circuits. Poor solder joints, over heated components.

Testing:
Plug the monitor in but do not activate the power switch so the backlight inverter circuits will be off. Check the 5vdc and the 12~24vdc to make sure they are OK. They should be tested with the load, you can use 6V 1A (6watts) lamp for the 5vdc, and car lamps such as 1157 (12v 8watts lo/26watts high) turn signal brake lamp using high filament connection for testing the 12~18vdc (or use two 1157 in series for 19~24vdc) for the backlight inverter circuits.
If the power supplies are working, the output voltages should be steady at the rated voltages. The power supply will go into shut down if it detects too much current draw due to false in the power supply or short circuits in the backlight inverter or in the logic board.

2) The backlight inverter circuits:
It takes the 12~24vdc and converts it to high frequency AC to drive the inverter transformers CCFL (Cold Cathode Fluorescent Lamp) assemblies. The transformers will drive the CCFL by applying the start up voltage (around 1500~2000v), when the CCFL start conducting, the voltage will drop down to about 500~800v.
The inverter has detection circuits to detect open circuit if the lamp is not attached or does not fire up after the start up voltage is applied, it will go into shut down. It will also shut down if the lamps draw too much current due to ages (when lamp gets old it will draw more current).
The inverter gets two signals from the logic board, one is the backlight ON/OFF signal, the other one is the Dimming signal for the lamps.
Common problems:
Bad filter caps, resonant caps (in the inverter output circuits), blown transistors/IC, shorted or open transformer winding.
Testing:
You should have spare lamps for testing the inverter circuits.

3) Logic board:
The logic board get the signals from the VGA (ANALOG) or DVI (DIGITAL) and processes them and feed them to the LCD panel T-CON (Timing Controller) board on the back of the LCD panel.
It also sends out two signals (backlight ON/OFF and Dimming) to the inverter circuits when the monitor is on and getting the signals from the PC.
If the logic board does not get the signal from the PC, it will put monitor into standby mode.
The 5vdc feeding it is converted to 3.3v, 1.8vdc by the switching buck converters to run the processor.
The logic board also sends the 5vd or 12vdc power for the T-CON board, if the voltage is not there, you will see white/grey glowing screen only.
Not much repair you can do on the logic board unless you have the full service manual and surface mount repair station.

4) CCFL and Inverter circuits testing:
If you don not have the inverter and lamp tester boxes you may be able to do a simple test by using these steps:
If the screen flashes on for a second, you can disconnect all the lamp connectors and connect it into one of the transformer output connector and see if you will see the flash on the screen, if you do, then try it with another transformer output connector to see if it also get the flash on the screen.
Repeat the procedure with other 3 lamps. If all the lamps do flash on for seconds then more likely the lamps are OK. If lamp only flash on one of the transformer output then you will know that the problem in that transformer inverter circuits.
If none of the lamps flash at all then the problem is in the inverter circuits, power supply, or not getting the on signal from the logic board.

Bad caps
http://i.fixya.nethttp://i.fixya.nete17e9cc.jpg

Power supply/inverter board (L), Logic bd. (R)
http://i.fixya.nethttp://i.fixya.netbc19983.jpg'

Dead T-CON bd, blown fuse. Get glowing screen only.
http://i.fixya.nethttp://i.fixya.net4fbd9e1.jpg

T-CON board's fuse F101
http://i.fixya.nethttp://i.fixya.net8506e44.jpg

Inverter board surface mounted fuses, F1 and F2

http://i.fixya.nethttp://i.fixya.net1bf6596.jpg
Bad lamps (Blackened ends, burnt /poor soldering)

http://i.fixya.nethttp://i.fixya.net5c8952e.jpg

http://i.fixya.nethttp://i.fixya.net4e5e9a1.jpg

Bad LCD panel (solid vertical lines)

http://i.fixya.nethttp://i.fixya.netffe90fe.jpg

Bad LCD panel due to bad T-CON board
http://i.fixya.nethttp://i.fixya.netef48b18.jpg
Failed TV and Monitors:
http://s807.photobucket.com/albums/yy352/budm
http://en.wikipedia.org/wiki/Capacitor_plague
Make your own test lamps: http://www.badcaps.net/forum/showthread.php?t=19987

on Sep 25, 2010 | Computers & Internet

1 Answer

Subwoofer makes noise like an untuned TV regardless of volume knob


I would suggest your crossover unit has failed in the speaker cabinet. The crossover circuit board separates the low and high frequency content of your stereos audio signal. The low frequencies go to the bass unit (woofer) and the high frequencies go to the tweeter speaker. If the capacitor on the crossover goes open or near open circuit then noise is introduced into the sound system. Replace either the capacitor or crossover unit.

Jan 18, 2014 | Cambridge Audio Minx X300 - Powered...

1 Answer

Samsung 2233RZ going black after 1-2sec


First if you can, try the monitor with other PC first to make sure it is not the PC problem.

If it behaves in the same fashion, then most probably has dying power supply due to bad DC filter caps, just see the top side of the caps to ensure it has not bulged up distorted.See the images bellow
12_24_2012_5_33_15_pm.jpg OR


12_24_2012_5_34_01_pm.jpg

Then there is the logic board. Plug the monitor in but do not activate the power switch so the backlight inverter circuits will be off. Check the 5vdc and the 12~24vdc to make sure they are OK. They should be tested with the load, you can use 6V 1A (6watts) lamp for the 5vdc, and car lamps such as 1157 (12v 8watts lo/26watts high) turn signal brake lamp using high filament connection for testing the 12~18vdc (or use two 1157 in series for 19~24vdc) for the backlight inverter circuits.
If the power supplies are working, the output voltages should be steady at the rated voltages. The power supply will go into shut down if it detects too much current draw due to false in the power supply or short circuits in the backlight inverter or in the logic board.

The backlight inverter circuits:
It takes the 12~24vdc and converts it to high frequency AC to drive the inverter transformers CCFL (Cold Cathode Fluorescent Lamp) assemblies. The transformers will drive the CCFL by applying the start up voltage (around 1500~2000v), when the CCFL start conducting, the voltage will drop down to about 500~800v.
The inverter has detection circuits to detect open circuit if the lamp is not attached or does not fire up after the start up voltage is applied, it will go into shut down. It will also shut down if the lamps draw too much current due to ages (when lamp gets old it will draw more current).
The inverter gets two signals from the logic board, one is the backlight ON/OFF signal, the other one is the Dimming signal for the lamps.
Common problems:
Bad filter caps, resonant caps (in the inverter output circuits), blown transistors/IC, shorted or open transformer winding.

If you are confident with your skill then go ahead else go to an authorized outlet for repairing
Do write back if you face any difficulty while working on the monitor

Dec 22, 2012 | Computers & Internet

1 Answer

My Yamaha SW118 keeps cutting out (volume reduces to v low level) even when driven by 500W amp. Doesn't seem to be the amp but not sure if the speaker has it's own internal protection. Can anyone advise?


Poly Switch
All full-range loudspeakers are fitted with a self-resetting
poly switch that protects the high-frequency driver from
damage caused by excessive power.
If a loudspeaker cabinet loses high-frequency output, immediately
remove power from the unit and wait for two to three
minutes. They should allow the poly switch to reset. Reapply
power and check the performance of the high-frequency
driver before continuing with the power reduced to a
level that does not cause the poly switch to interrupt the signal.
On the SW115V/SW118V/SW218V sub woofer, the Poly
Switch protects the woofer and a similar routine should be
followed if its output is lost.

Aug 29, 2010 | Yamaha SW118-IV 18" Subwoofer Speaker

2 Answers

I am trying to find the output power, watts?


bad transformer. A $10 part at most electronic stores. U fried it when you dropped it. Happens all the time.

Jun 08, 2010 | Audio Players & Recorders

2 Answers

Where is the fuse inside the power supply model fsp200


The unit is only 200watt and the fuse cost about $2,Thats if there one built into it,
The replacement power supply is about $20-00 NZD
Probably 20minutes to fix (for a novice) depending on their skill level and tools available,

BEST ADVICE Replace it

Power is something you dont want to mess with because it can kill.
The power packs are replaceable but people arent.
Be very careful and dont mess with the power.

I am an Electrician and I respect power.Misterdj

Mar 24, 2010 | AOpen (FSP200-60SAV) 200-Watt Power Supply

2 Answers

How many watts is it


http://www.kenwoodusa.com/UserFiles/File/Global/Consumer/Manuals/kac528.pdf

Page 7 of the manual gives you all the different configurations of this amp, and it's MAX power. FYI; Kenwood rates their amps at MAX power, not clean. Hope this helps.

Sep 30, 2009 | Kenwood KAC-628 Car Audio Amplifier

1 Answer

Do you have instructions for wiring install on volfenhag GX8200??


Amplifier Class AB
Number of Channels 2
RMS Power (4 ohms) 120 watts x 2 channels
RMS Power (2 ohms) 200 watts x 2 channels
RMS Power (1 ohm) Not Stable
Bridged RMS Power 400 watts x 1 channel
Total RMS Power Output 400 watts
Peak Power Output 1000 watts watts x 1 channel
Minimum Impedance Unbridged 2 ohms
Minimum Impedance Bridged 4 ohms
THD at Rated RMS Power 0.1%
Speaker Level Inputs No
Preamp Outputs 1 pair
Built-in Crossover High-pass (HP), Low-pass (LP), Full (AP)
High-Pass Crossover Frequency 40 - 250 Hz
Low-Pass Crossover Frequency 40 - 250 Hz
Subsonic Filter N/A
Signal-to-Noise Ratio N/A
Channel Separation N/A
Bass Boost 0 - 18 dB
Bass/Gain Remote Yes
Fan Cooled Yes
Fuse Rating 20A x 2

Dec 24, 2008 | Volfenhag ZX-8200 Car Audio Amplifier

1 Answer

V12 MRV-1507 or Xplod? Amplifier - XM-ZR1252 good quality sound


Alpine is just a better brand in general. I have the older MRV-1507, sounds GREAT, i have had friends who has had the Explode line, but it was always a temporary system until they got something better, like the alpine or kenwood.

Aug 14, 2008 | Car Audio & Video

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