LG Electronics TL-AT130M service manual Adjustment after Replacing Drum Assembly Video Heads

DECK MECHANISM ADJUSTMENT

7. Adjustment after Replacing Drum Assembly (Video Heads)

Purpose: To correct for shift in the Roller Guide and X value after replacing the Drum.

Test Equipment/ Fixture	Connection Point	Test Conditions	Adjustment Points
		(Mechanism Condition)
• Oscilloscope	• CH-1: PB RF Envelope	• Play the Blank Tape	• Guide Roller Precise
• Alignment Tapes	• CH-2: NTSC: SW 30Hz	• Play an Alignment Tape	Adjustment
• Blank Tape	PAL: SW 25Hz		• Switching Point
• Post Height Adjusting Driver	• Head Switching Output		• Tracking Preset
• Screw Driver(+) Type 5mm	Test Point		• X-Value

•RF Envelope Output Test Point

Checking/Adjustment Procedure
		Connection Diagram					OSCILLOSCOPE
Play a blank tape and check for tape curling or creasing around
the Roller Guide. If there is a problem then follow the procedure
	RF ENVELOPE OUTPUT TEST POINT
4. "Guide Roller Height" and 5. "Audio Control(A/C) Head
							CH1 CH2
Adjustment".		HEAD SWITCHING OUTPUT TEST
		POINT
			Waveform
			V1/V MAX E 0.7
				V1	V	V2
			V2/V MAX E 0.8
			RF ENVELOPE OUTPUT

Fig. C-7

8. Check the Tape Travel after Reassembling Deck Assembly.

8-1. Checking Audio and RF Locking Time during playback and after CUE or REV (FF/REW)

Test Equipment/ Fixture	Specification	Test Equipment	Test Conditions
		Connection Points	(Mechanism Condition)
		Connection Points
• Oscilloscope	• RF Locking Time: Less than 5	• CH-1: PB RF Envelope	• Play an Alignment Tape
• Alignment Tapes(with 6H	sec.	• CH-2: Audio Output	(with 6H 3kHz Color Bar
3KHz Color Bar Signal)	• Audio Locking Time:Less than	• RF Envelope Output Point	Signal)
• Stop Watch	10sec	• Audio Output Jack

Checking Procedure	NOTES:
Play an Alignment Tape then change the operating mode to	1)	CUE is the forward search mode
CUE or REV and confirm if the unit meets the above listed	2)	REV is the backward search mode
specifications.	3)	Refer to the Play mede

8-2. Checking for tape curling or jamming

Test Equipment/ Fixture	Specification	Test ConditionsVCR(VCP)(MechanismState Condition)
• T-160 Tape	• Be sure there is no tape jamming or curling at	• Run the CUE, REV, Play mode at the
• T-120 Tape	the begining, middle or end of the tape.	beginning and the end of the tape.

Checking Procedure

1) Confirm that the tape runs smoothly around the roller	2) Confirm that the tape passes over the A/C Head
guides, Drum and A/C Head Assemblies while abruptly	Assembly as indicated by proper audio reproduction and
changing operating modes from Play to CUE or REV.	proper tape counter performance.
This is to be checked at the begining, middle and end
sections of the tape.

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