Dell 21N21E2 Electrical Adjustments, Constant Voltage, VCO Coase L1, VCO Fine L1, AGC Voltage

ELECTRICAL ADJUSTMENTS

1. ADJUSTMENT PROCEDURE

Read and perform these adjustments when repairing the circuits or replacing electrical parts or PCB assemblies.

CAUTION

•Use an isolation transformer when performing any service on this chassis.

•Before removing the anode cap, discharge electricity because it contains high voltage.

•When removing a PCB or related component, after unfastening or changing a wire, be sure to put the wire back in its original position.

•When you exchange IC and Transistor for a heat sink, apply the silicon grease on the contact section of the heat sink. Before applying new silicon grease, remove all the old silicon grease. (Old grease may cause damages to the IC and Transistor).

Prepare the following measurement tools for electrical adjustments.

1.Oscilloscope

2.Digital Voltmeter

3.Pattern Generator

On-Screen Display Adjustment

1.In the condition of NO indication on the screen. Press the VOL. DOWN button on the set and the Channel button (9) on the remote control for more than 2 seconds to appear the adjustment mode on the screen as shown in Fig. 1-1.

35	H POSI OSD	120
36	V POSI OSD	57
37	H POSI TEXT	119
38	V POSI TEXT	57
39	H POSI 60	34
00 CUT OFF			VCO Status -
	9- EXT
			MMM

Fig. 1-1

2.Use the Channel button (0-9)or Channel UP/DOWN button on the remote control to select the options shown in Fig. 1-2.

3.Press the MENU button on the remote control to end the adjustments.

NO.	FUNCTION	NO.	FUNCTION
00	CUT OFF	20	TINT
01	RF AGC	21	SHARP
02	AGC GAIN	22	CONTRAST CENT
03	R DRIVE	23	CONTRAST MAX
04	R CUTOFF	24	CONTRAST MIN
05	G DRIVE	25	COLOR CENT
06	G CUTOFF	26	COLOR MAX
07	B DRIVE	27	COLOR MIN
08	H POSI (50)	28	M R CUT OFF
09	V POSI (50)	29	M G CUT OFF
10	V POSI (60)	30	M B CUT OFF
11	V SIZE (50)	31	CVBS OUT
12	V SIZE (60)	32	APR THRESHOLD
13	VCO COARSE	33	BELL FILTER
14	VCO FINE	34	BANDPASS
15	VCO COARSE L1	35	H POSI OSD
16	VCO FINE L1	36	V POSI OSD
17	BRIGHT CENT	37	H POSI TEXT
18	BRIGHT MAX	38	V POSI TEXT	Fig. 1-2
19	BRIGHT MIN	39	H POSI (60)

D-1

2. BASIC ADJUSTMENTS

2-1: CONSTANT VOLTAGE

1.Place the set with Aging Test for more than 5 minutes.

2.Connect the digital voltmeter to TP501.

3.Set condition is AV MODE without signal.

4.Adjust the VR501 until the DC voltage is 117 ± 1.0V.

2-2: VCO

1.Place the set with Aging Test for more than 10 minutes.

2.Connect the oscillator (38.9MHz) to TP001.

3.Activate the adjustment mode display of Fig. 1-1and press the channel button (13) on the remote control to select "VCO COARSE".

4.Press the VOL. +/- button on the remote control until the "OK" appear on the screen. If the "OK" is not displayed, select the "+" side on the changed from "+" to "-".

5.Press the Page UP button once to set to "VCO FINE" mode.

6.Press the VOL. +/- button on the remote control to select the 5 step down point from the upper limit on the "OK".

(Example: In case of the "OK" range 30~41, select 36.)

2-3: VCO COASE L1, VCO FINE L1

1.Place the set with Aging Test for more than 10 minutes.

2.Connect the oscillator (33.95MHz) to TP001.

3.Activate the adjustment mode display of Fig. 1-1and press the channel button (15) on the remote control to select "VCO COARSE L1".

4.Press the VOL. +/- button on the remote control until the "OK" appear on the screen. If the "OK" is not displayed, select the "+" side on the changed from "-" to "+".

5.Press the Page UP button once to set to "VCO FINE L1" mode.

6.Press the VOL. +/- button on the remote control to select the 5 step down point from the upper limit on the "OK". (Example: In case of the "OK" point 30~41, select 36.)

2-4: AGC VOLTAGE

1.Place the set with Aging Test for more than 15 minutes.

2.Receive the UHF (63 ± 1dB).

3.Connect the digital voltmeter to pin 5 of CP101.

4.Activate the adjustment mode display of Fig. 1-1and press the channel button (01) on the remote control to select "RF AGC".

5.Press the VOL. +/- button on the remote control until the digital voltmeter is 2.55 ± 0.05V.

2-5: FOCUS

1.Receive a 70dB monoscope pattern.

2.Turn the Focus Volume fully counterclockwise once.

3.Adjust the Focus Volume until picture is distinct.

2-6: CUT OFF

1.Set condition is AV MODE without signal.

2.Using the remote control, set the brightness and contrast to normal position.

3.Place the set with Aging Test for more than 15 minutes.

4.Activate the adjustment mode display of Fig. 1-1and press the channel button (00) on the remote control to select "CUT OFF".

5.Adjust the Screen Volume until a dim raster is obtained.