Samsung CF21M Troubleshooting

5 Troubleshooting

5-1 Parts Level Troubleshooting

Notes: 1. If a picture does not appear, Click the Brightness and Contrast button on the front panel, and then increase the value

of Brightness and Contrast.

2. Check the following circuits.

• No raster appears: Power circuit, Horizontal output circuit, H/V control circuit, and H/V output circuit.

• High voltage develops but no raster appears: Video output circuits.

• High voltage does not develop: Horizontal output circuits.

5-1-1 No Power Supply

Check and replace FG601, D601,

D701, Q701, IC601 and ZD601.

Check the Voltage at

C607 plus polarity point.

Is the Voltage 400VDC?

with PFC : 400VDC

without PFC : it is different

according to input voltage

Yes

No

Check and replace

FG601, D601, D703.

IC601 Pin 1 waveform is right?

Yes

The secondary voltage of

T601 is right?

(Is it same the schemetic diagram)

Yes

Check IC651 (KA78R12) Pin 12?

•

Is the voltage 12VDC?

•

Yes

Done.

No

No

No

Check and replace

IC601, ZD601, D606, IC701.

Check TR, IC and biode

related to every B+line.

Appear 4VDC Pin 4 of IC651?

No

Check and Micom. (IC201)

•

Check and replace IC651.

•

Check every IC connected to 12V.

Yes

CF21M* 5-1

5 Troubleshooting

5-1-2 PFC Failure

Check the Voltage at IC701 Pin5.

The Voltage is around 10VDC?

Yes

1

Q701 Gate waveform is right?

Yes

Check the Voltage at D701 cathode.

The Voltage is about 400VDC?

Yes

Done.

5-1-3 DPMS Failure

Check signal source

H/V sync. video signal.

No

No

No

Check and Replace D702,

R711, ZD705, ZD706.

Replace IC701.

Replace Q701, D701.

WAVEFORMS

368 V (IC601, #1)

1

Make No H/V sync.

( That is power off mode).

LED blinks?

Does +12V Line off?

(Check the IC651 output Pin 2)

Yes

Does +14V_V Line off?

(Check the Q670 Collector)

Yes

Does the Q620 activate?

Yes

Done.

No

No

No

Check IC201 Pin 25

or replace IC201.

Check Q671, D670.

Check IC201 Pin 23

or replace IC201.

5-2 CF21M*

5-1-4 H_Deflection Failure

5 Troubleshooting

IC402 Pin 6 waveform is right?

2

Yes

3

Q454 drain

waveform is right?

Yes

4

Q401 gate, drain

5

waveforms are right?

Yes

Q402 base, collector

6

7

waveforms are right?

WAVEFORMS

No

No

No

No

1. Appear the Voltage 12VDCat
IC402 Pin 7 replace R451.

2. Check IC402 Pins 6~5, 7~6.

3. Replace IC402.

Check Q451, Q452, Q453,

ZD450, R467, D456.

Check Q250, Q251, IC250

Check +19V line.

Check and replace D402 and Q402.

Check DY connector connection.

IC402, #6

2

CH1 P-P = 10.96 V CH1 RMS = 6.180 V

Q401, Drain

5

Q454, Drain

3

Q402, Base

6

Q401, Gate

4

CH1 P-P = 11.6 V CH1 RMS = 6.944V

Q402, Collector

7

CF21M* 5-3

5 Troubleshooting

5-1-5 S Correction Failure

Check S1 ~ S5 signal.

Refer to the S-corrction table page?

S1~S5 signals are right at

each frequency block?

Yes

Check and replace

C411, C413, C414, C415, C416,

C417, C418, Q403 ~ Q407, Q408 ~ Q412

5-1-6 H_Lin. Failure

IC201 Pin 3 voltage varies with

different H_Lin. DAC values?

Yes

IC403 Pin 7, 8 voltage varies with

different H_Lin. DAC values?

Yes

No

No

No

Check and replace IC201.

Replace IC201.

Check +12 V line.

Check some parts around IC403.

Check L403.

5-1-7 Invariable H_Size

D250 Cothode voltage varies with

different H_Size DAC values?

Yes

IC402 Pin 6 output duty varies with

different H_Size DAC values?

No

No

Check and replace IC250, IC201.

Check some parts

around IC250, IC201.

5-4 CF21M*

5-1-8 Abnormal H_Size

5 Troubleshooting

WAVEFORMS

The Voltage waveforms at

7

Q402 Collector are right?

Yes

T402 pin 8 wareform is right?

8

Yes

Check some parts around

IC250 and IC402 Pin 1 and 2.

5-1-9 Side Pin or Trap Failure

IC250 Pin 24 output exists?

9

The waveform is right?

Yes

No

No

No

Repeat the troubleshooting

Guide of H_deflection failure.

Replace T402.

Check and replace IC250.

Q402, Collector

7

T402, #8

8

Check and replace IC402.

Check some parts IC402 Pin 2

and IC250 Pin 24.

5-1-10 Para. or Pin Balance Failure

IC250 Pin 24 output varies with

different DAC values?

No

Replace IC261.

WAVEFORMS

IC250, #24

9

CF21M* 5-5

5 Troubleshooting

5-1-11 Tilt Failure

Check tilt connector connection

IC201 Pin 5 output duty varies

with different DAC values?

Yes

IC403 Pin 10, 11 output varies with

different DAC values?

Yes

Check and replace CRT.

5-1-12 V Deflection Failure

Is 14V at IC301 Pin 2?

Is -14V at IS301 Pin 5?

Yes

No

No

No

Check and replace IC201.

Check and replace IC403.

Check and replace R312, R316.

Refer to 5-1-1 No Power supply.

WAVEFORMS

IC250, #23

10

IC250 Pin 23 output exists?

10

The waveform is right?

Yes

IC301 Pin 6 output exists?

11

The waveform is right?

Yes

Check V DY connector connection.

No

No

Check and replace IC250.

Check and replace some

parts around IC301.

IC301, #6

11

5-6 CF21M*