Samsung PN50B450B1DXZA Specifications download pdf (Page 14)

In this issue and next month’s issue, we examine basic troubleshooting for Samsung Plasma TVs.

First, Take the VITAL SIGNS: Vs, Va, Vsc, and Ve (on most models)

When you walk into a doctor’s office, the first thing they do is check your vital signs. You should do the same when trou-

bleshooting Plasma TVs. You can take a Plasma TV’s vital signs - the Vs, Va, Vsc, and Ve voltages - in less than 5 min-

utes. Not only will this help you make the immediate repair diagnosis, but will also prevent failures in the future. (Redos!)

Look for the Label

These “vital sign” voltages are so important that their values are printed on a sticker inside the back of each panel. The

values are specifically set for each panel. A label example is below:

Note that the new 2010 models have additional failsafe circuitry that shuts down the start up sequence in approximately

3 seconds if there is an over voltage or an under voltage/high current condition (a short). However, you still have plenty

of time to check the readings. Simply hook up your volt meter before you turn on the TV, and be ready to take your read-

ings.

Let’s look at some of these voltages and what they do.

Vs – The Sustain Voltage

Operating at approx 200 volts (sticker example, 212V), the sustain voltage is generated by the SMPS (Switching Mode

Power Supply) and is used by both the Y-Main and X-Main assemblies to help produce the sustain drive signal to the

plasma cells of the panel. Without the Vs voltage, the drive signal cannot exist and the cells cannot light.

Repair Scenario 1

Symptom: No Video, dark screen. TV shuts off after 3 seconds.

Troubleshooting: Measuring Vs reveals no voltage.

Repair: Remove all power and isolate the Y-Main and X-Main from the Power Supply Vs by removing their associated

connectors, and then check for a short condition with an ohm meter. (Note that the Vs is fed to the X-Main via the Y-Main

in the new models). Replace the shorted Assembly. Also check the operation of Vs at the SMPS by powering the TV on

with the connectors still removed to determine if the power supply is operational. In most cases, a switching mode power

supply will not be damaged even by a shorted Vs.

Page 14

Volume 4, Issue 10 Consumer Electronics Newsletter Samsung Tech Talk

Plasma TV Repair Made Simple

Charles Russo

Trainer—RTSC

NTSC NTSC/PAL

Va Vsc Vs Ve

55 -190 212 100

Rev. 2.0

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Samsung PN50B450B1DXZA Specifications Page 14