SAMSUNG 793DF Service Manual Troubleshooting

5 Troubleshooting

5-1 Parts Level Troubleshooting

Notes: Check the following circuits.

• No raster appears: Power circuit, Horizontal 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 D601 and FH1

Chirping noise exists?

No

Repeating start?

No

1

IC601 Pin 1 waveform is right?

Yes

C627 Voltage is 13 V ± 0.5V?

Yes

Yes

No

No

Check and replace IC601.

Check and replace D606.

Check and replace IC601.

Check and replace IC201,

IC301, IC401, Q590, Q490,

and 12V regulator circuit.

WAVEFORMS

332 Vpp (IC601, #1)

1

Yes

Normal operation?

Yes

Verify voltages.

Done

LE15V*/LE17LS/LE17LT/
LE17KS/LE17KT/LE17JS/LE17JT

No

Replace main board.

5-1

5 Troubleshooting

5-1-2 DPMS Failure

Check signal source

H/V sync. video level.

Make no H/V Sync. (power off mode)

LED blinks?

Yes

+12 V line off?

Yes

2

IC601 Pin 1 output

voltage exists?

Yes

No

No

No

Check IC201 Pin 40.

Check IC201 Pin 5/Pin 6 and

Q624, Q625 operation.

Refer to 5-1-1 no power supply.

WAVEFORMS

332Vpp (IC601, #1)

2

Done

5-2 LE15V*/LE17LS/LE17LT/

LE17KS/LE17KT/LE17JS/LE17JT

5-1-3 H_Deflection Failure

5 Troubleshooting

Does PWM output signal appear

3

at Pin 28 (B_DRV) of IC401?

Yes

Does horizontal pluse signal

4

appear at Pin 26 of IC401?

Yes

Does 110 Vp-p signal appear

5

at Collector of Q401?

Yes

Check Q590, Q490 and T401.

No

No

No

Does DC 12V appear at

Pin 29 of IC401?

Yes

Check IC401.

Check IC401.

Check Q401.

No

Check 12 V line.

WAVEFORMS

12 Vpp (IC401, #28)

3

2.00V (IC401, #26)

4

5-1-4 S Correction Failure

Check S1 ~ S3 signal.

S1~S3 signals are correct at each

frequency block?

Yes

Check and replace Q451, Q452,
Q453, Q454, Q458, Q457, Q456,
Q455, D451, D452, D453, D454.

No

Check and replace IC201.

78 Vpp (Q401, Collector)

5

LE15V*/LE17LS/LE17LT/
LE17KS/LE17KT/LE17JS/LE17JT

5-3

5 Troubleshooting

5-1-5 H_Lin. Failure Check and Replace L441 (Fix Type)

5-1-6 Invariable H_Size

IC401 Pin 28 voltage varies with

different B_DRV DAC values?

Yes

Q590 gate output duty varies with

different B_DRV DAC values?

5-1-7 Abnormal H_Size

IC401 Pin 24 output duty

varies with different B+ offset

DAC values?

Yes

6

Q490 collector

waveform is right?

No

No

No

No

Check and replace IC401.

Check some parts around Q590,

Pin 14~16 of IC401.

Check and replace IC201, IC401.

Check and replace Q411,

Q412, Q413, and Q414.

WAVEFORMS

1300 Vpp (Q490, Collector)

6

Yes

Check components

around D405 and L411.

5-4 LE15V*/LE17LS/LE17LT/

LE17KS/LE17KT/LE17JS/LE17JT

5-1-8 Side Pin or Trap Failure

5 Troubleshooting

7

IC401 Pin 24 output exists?

Yes

Refer to 5-1-7

abnormal H_Size

.

5-1-9 Para. or Pin Balance Failure

IC401 Pin 24 output varies with

different DAC values?

No

Replace IC401.

No

Yes

Check and replace IC401.

Refer to 5-1-7

abnormal H_Size

WAVEFORMS

0.44 Vpp (IC401, #24)

7

.

5-1-10 Tilt Failure ( Only 17” Function)

Check tilt connector connection

IC201 Pin 20 output duty varies

with different DAC values?

Yes

Q323 Base output varies with

different DAC values?

Yes

Check and replace Q321 and Q322.

No

Check and replace IC201.

No

Check and replace Q323.

LE15V*/LE17LS/LE17LT/
LE17KS/LE17KT/LE17JS/LE17JT

5-5

5 Troubleshooting

5-1-11 V Deflection Failure

13V and –10V lines are on?

Yes

No

Refer to 5-1-1 no power supply

WAVEFORMS

2.5 Vpp (IC401, #23)

8

IC401 Pin 23 output exists?

8

Yes

9

IC301 Pin 6 output exists?

Yes

Check DY connector connection.

No

No

5-1-12 V Size or Position Variation Failure

IC401 Pin 23 output varies with

different DAC values?

No

Check and replace IC401.

Check and replace

components around IC301.

Check and replace IC201 and IC401.

50 Vpp (IC301, #6)

9

Yes

Check and replace IC301.

5-6 LE15V*/LE17LS/LE17LT/

LE17KS/LE17KT/LE17JS/LE17JT