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Syncmaster 206bw blinks on and off

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  • Flat Panel Monitors
  • Syncmaster
  • Peripherals
Last response: in Computer Peripherals
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January 5, 2010 3:53:42 PM

syncmaster 206 bw blinks on and off

More about : syncmaster 206bw blinks

Anonymous
February 2, 2010 12:53:56 PM

Same problem here :) 
Seems to get better once the monitor warms up.

I Suspect that this is a fault in the power supply/ inverter circuit,
probably due to a leaky electrolytic capacitor. The ON/OFF switch
or the power LED has nothing to do with it.

Computers, Monitors, Televisions (and most other modern appliances) no longer
use mechanical ON/off switches, in favor of an electronic circuit based on
digital logic and a relay.

The monitor has two separate power supplies:

1) An ultra-low power supply circuit which is ALWAYS on.
This circuit provides a small amount of power to the digital
logic chip which in turn controls the MAIN power supply through
a relay or some other form of indirect switching.

2) The main power supply, which provides operating power to the rest
of the monitor.
--
Both power supplies contain one or more of the following components:

a) A transformer (or external AC adapter) which provides electrical ground
isolation from the incoming AC line for safety reasons

and

reduces the operating voltage from 117 Volts AC to a lower and safer
level (e.g. 12 volts for internal consumption by the monitor).

b) A rectifier, which converts AC to DC.

c) Filter capacitors to smooth out the resulting DC.

d) Voltage regulators to make the DC more constant and precise.

e) The circuit may also contain over-current, over-voltage or other
automatic fault detection to protect the monitor from catastrophic
failure.

f) The monitor may also detect the lack of video input and automatically
shut itself of after a few minutes.
--
The reason I am telling you all this, is that the power supply control
logic in a modern monitor can get very complicated, but fortunately
these circuits a quite reliable, and not a typical cause of failure.
Also the entire circuit is typically implemented in a single silicon
chip with very few external components.
--
The one weak link in the system are the filter capacitors, which
consist of two sheets of ultra-thin metal foil wound up in a spool,
separated by some sort of an ultra thin insulator.

The larger the area of the two foils and the thinner the insulation
between them, the higher the capacitance:
i.e. the better the filter.

In the case of modern electrolytic capacitors, the insulation is only
a few atoms thick, often created by a chemical reaction between the
metal foil and special fluid bathing the spools. The whole thing looks
like a tiny, narrow but tall can of sardines.

For this reason, electrolytic capacitors are also polarized +/-.
If you insert them backwards into a circuit, they will explode
(literally !)

In the case of solid tantalum capacitors, which look like a tiny
teardrop with two leads coming out of it, this explosion can
be very loud and violent, like a shot-gun going off. The capacitor
gets totally vaporized, nothing left except two leads sticking out
of the circuit board, where the capacitor once was. I suppose that
the shrapnel an debris could severely damage your eyes on
a bad day. When ever I power up a circuit board, I always look
the other way.

If these capacitors are operated too close to their maximum
voltage or if they are overheated during normal operation,
the thin insulating layer will fail, resulting in leakage current.
The voltage will drop and the monitor will not work, or the
power supply control logic will detect the fault and fail to
operate.

Similarly, if the monitor is not used for a long time, the lack
of voltage will cause these capacitors to dry out.
Once again the insulating layer will fail.

Sometimes, a defective capacitor is obvious:
1) It is totally gone, exploded, vaporized right off the circuit board.
2) It is swelled up and leaking.
3) It is discolored...

But many times there is no physical indication at all!

In this case you need to get a service manual or at least a schematic
for the monitor and measure a few voltages around the power supply
circuit. This requires a good voltmeter, and perhaps an Oscilloscope.
The former is cheap, the later very expensive.

Ultimately you need some knowledge of electronics to identify
the bad capacitor, so you can replace it. Then you need good
soldering skills. The capacitors them-selves, are standard parts,
easily available, and dirt cheap.

If the monitor starts working after a while do NOT shut it off.
The capacitor may heal itself.
Good luck.
m
0
l
November 3, 2010 8:03:22 PM

It's caused by three bad capacitors. See the site for fixing it yourself. http://normsweb.com/tektips/sam206bw.shtml.

I just fixed mine last night. It works now like a new one.

Purchase the three capacitors at www.futurlec.com
(2) 1000uf 25v Radial 105oC Electrolytic Capacitor 2x$0.35 = $0.70
(1) 470uf 25v Radial 105oC Electrolytic Capacitor 1x$0.20 = $0.20
Shipping from Thailand (It only took about a week to reach St. Louis, MO) $4.00

Buy a soldering gun from Amazon.com, it comes with a coil of solder
Weller SP23LK Marksman 25 Watt Soldering Iron Kit = $14.55 w/ 7-years warranty
Shipping is free if your total purchase is over $25 with other items you need on the Amazon.

Therefore, your total cost is less than $20 USD. It will enable you to fix the problem once for all.

I noticed that the soldering gun need to be switched with a flat head first, (it comes with in the package), in order to soften the existing solder to remove the old and blown-off capacitors. Then switch back to needle style head at soldering gun to weld the new capacitors in place.

Please note that existing soldering is hard to be softened. You need to be patient to place the flat head soldering gun for a quite long time. The existing solder will be melted. At first I thought my gun is not hot enough to melt the old solder. So, be patient.

m
0
l
Related resources
April 6, 2011 3:18:43 AM

hi, the link doesn't work anymore, is it possible for you to send me a picture of the board with an indication of the defective capacitors? (i'm asking that, beacause i guess this picture was on the page). I'd like to repair my screen, i have no money to buy a new one and this one do a great job!

Thank you!
m
0
l
December 6, 2011 12:47:46 AM

The link does work, just make sure that you do not have a full stop . at the end of the link. (eg: .shtml not .shtml. )

if you still cant get there, goto normsweb.com, click on tektips, and scroll down to the 206BW link and click it.
m
0
l
!