CT331HBZX Samsung CRT TV [NTSC] - How to enter service mode, adjustments and Circuit diagram

Applicable to Samsung CT331HBZX- CT501EBZX - CT331EBZX - CT501HX - CT331HBX - CT5066BZX - CT331HX - CT5038ZX - CT3366BZX - CT3338ZX [Chassis K15A]

Used ICs: KA2131(Vertical amp) – KA350765R(SMPS-STR) – KA21638(chroma-jungle) – Z8933412PSC(Micom) – 24C020(Memory) – LA4425(audio output amplifier)

FBT OPTION

14” = AA26-300005H, 20” = AA26-300005F, 21” = AA26-30005F

Service Mode Menus

Since there are no VRs in the K15A chassis, all adjustments after parts replacement must be done in the Service Mode. Service Mode adjustments are necessary when either the EEPROM (IC902) or the CRT is replaced.

Entering the Service Mode

Press the following transmitter keys while in STAND-BY mode:

MUTE > 1 > 8 >2 > POWER

“Factory Mode Menu” is displayed.

Enter Service Mode using the Volume + / - keys.

Select a mode to be adjusted, using the channel down key.

Change the data with “Volume + / -- “ keys.

Return to the Service mode by pressing MENU.

Return to the Factory mode via the MENU key.

Press POWER to enter the Stand-by mode.

SMPS and deflection circuit diagram [Click on the pictures to zoom in]

Chroma jungle schematic

Micom schematic

PWB

Adjustment in Option Mode

This adjustment is necessary whenever the EEPROM is replaced. Input data (as marked on the back cabinet).

Select “SET OPTION” by pressing the Channel “Dn” key twice.

Press the Volume + / -- keys to enter the set Option mode.

Press MENU to go back to the factory mode.

Select RESET with channel “Dn” key.

Press volume + key. [Power Off].

Service Mode Adjustments

1. The Pattern Adjustment is done only in the factory. Do not attempt to readjust it.

2. Refer to 4-2 for other adjustments.

3. Set OPTION data.

Service Mode Adjustment Ratings

General Alignment

Usually, a color TV needs only slight touch-up adjustment upon installation. Check the basic characteristics such as picture height, focus and a horizontal and vertical sync.

Observe the picture and check for good back and white details. There should be no objectionable color shading: If color shading is present, demagnetize the receiver. If color shading persists, perform purity and convergence adjustments.

Power Supply Check

A: Power plug is connected; “Stand-by” mode
B: Power On when “Power ON” button is pressed
C: Power On by FBT Each supply is marked on its lead-in wire.

Fail Safe Circuit Check (FS) (OPTION)

1. The fail-safe check must be the final step in servicing.
2. Turn the power switch ON and adjust customer controls for normal operation.
3. Temporarily short pin X to pin R on the main board (RX06, RX04) with a jumper wire.  Raster will disappear.
4. The TV must remain in this state even after removing the jumper wire. This shows that the failsafe circuit is working properly.
5. To recover picture and sound, temporarily turn off the TV and allow the failsafe circuit more than 30 seconds to reset. Then switch power ON to produce normal picture and sound.

IC902 Replacement

1. When IC902 is replaced, all values are reset to “Initialized MICOM Data” and readjustment is necessary.

2. Press the POWER button 10 seconds after plug-in.

RF-AGC Adjustment

1. Input a PHILLIPS pattern.

2. Set the input signal to 60 dB.

3. Enter into the AGC in the service mode.

4. Adjust AGC until color bar noise disappears.

Sub-Contrast Adjustment

1. Input a gray scale pattern. Use a pattern generator (PM5518).

2. Short D208 to switch off the ABL feed-back.

3. Check CN201 R-OUT with an oscilloscope.

4. Set RC, BC, GC data to 0 in the Service Mode.

5. Adjust SCT to 2.40 ± 0.1Vp-p

6. Remove the short across D208 and restore ABL.

Sub-Tint Adjustment

1. Input a rainbow pattern.

2. Check CN201 B-OUT with an oscilloscope.

3. Adjust STT in the service mode until the 6th peak is the highest and the 5th and 7th peaks have equal heights.

Sub-Color Adjustment

1. Do sub-color adjustment after the SubContrast and Sub-Tint adjustments.

2. D208 should still be shorted. The ABL should still be switched OFF.

3. Input a color bar pattern. Use a pattern generator (PM5518).

4. Check CN201 R-OUT (use an oscilloscope).

5. Ensure that the RC, GC and BC data are 0.  BG are 140 and GG should be 90.

6. Adjust SCR to 2.4 ± 0.1Vp-p (black and red levels).

7. Remove the short across D208 and restore ABL.

White Balance Adjustment

LOW-LIGHT ADJUSTMENTS
1. Input either a lion head or “pure white” color pattern.
2. Operate the receiver for 30 minutes.
3. Check the data in the service mode:
RC, GC, BC are 0 and SB is 16; Steps BG are 90 and GG are 140.
4. Enter the horizontal line mode by pressing the MUTE key.
5. Adjust the screen VR on the FBT until a dim colored line (red, green or blue) appears on the screen.
6. After pressing the MUTE key, go to RC,BC or GC with channel UP|Dn, keys. After putting a dim colored line (red, green or blue) in the horizontal line with MUTE key, adjust color with volume Up|Dn , keys.
7. Exit the horizontal line via the MUTE key.

HIGH-LIGHT ADJUSTMENTS
1. Input a high-light pattern
2. Adjust GG,BG in the Service Mode.
3. Recheck in low light.

Sub-Brightness Adjustment
1. Input a Toshiba pattern.
2. Warm up the receiver for 10 minutes.
3. Enter the Service Mode and set SB to the point where the 5th point is brighter in the gray scale.

Vertical Size Adjustment
1. Input a lion head pattern.
2. After the vertical center adjustment, enter into the service mode.
3. Adjust VA so that the each top and bottom of the screen is 4.0. If the top and bottom values are different, adjust VA so that the sum of the two values is 8.0.

Horizontal Size Adjustment
1. Receive a lion head pattern.
2. Enter into the service mode.
3. Adjust HS to symmetrized right and left

When CRT Is Replaced
Do the following adjustments after the basic purity and convergence adjustments.
1. White Balance
2. Sub-brightness
3. Vertical Size
4. Horizontal Size
5. Fail safe (should be the final step).