LG / GOLDSTAR P934I
Service Manual

GOLDSTAR P934 I
Mechanism Adjustment Cont�d
Adjustment Points Tilt Adjustment Screw(C) Height Adjustment Screw(B) Azimuth Adjustment Screw(A) Adjustment Procedure/Diagrams 1) Initially adjust the A/C head assembly as shown in figure C-6-1, by using the height adjustment screw(B). 2) Play a blank tape and observe if the tape passes accurately over the A/C head without tape curling or folding. 3) If folding or curling does occur then adjust the Tilt adjusting screw(C) while the tape is running to resemble figure 0-6-3. 4) Confirm that the tape passes over the A/C head assembly as indicated by proper audio reproduction and proper tape counter performance. NOTE Ideal A/C head height occurs, when the tape runs between 0.2-0.25mm above the bottom edge of the A/C head core. the clockwise direction to eliminate tape the curling. (2) If folding is observed at the upper part of the T/UP post, then slowly turn the tilt adjustment in the counterclockwise direction to eliminate the tape curling. C. RF Fine Adjustment (only if the RF waveform differs from figure C-5-3). 1) Check the RF Envelope after confirming smooth tape transport path at the T/UP Guide/ Pinch Roller. D. Precise Adjustment (Azimuth adjustment) Test Equipment/Fixture Oscilloscope Alignment tapes Screw Driver(+) Type 5mm Test Equipment Connection Point Audio output jack Test Conditions VCR (VCP) State Play an alignment tape 1 KHz, 7KHz sections. Adjustment Points Azimuth Adjustment Screw(A) Tilt Adjustment Screw(C) Adjustment Procedure 1) Connect the probe of oscilloscope to Audio Output Jack. 2) Alternately adjust the Azimuth adjustment screw(A) and the Tilt adjustment screw(C) for maximum output of the 1 KHz and 7KHz segments, while maintaining the flattest envelope differential between the two frequencies.

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envelope. This method should allow the 30um head to be centrally located over the 60um tape track. 4) Tighten the A/C head assembly mounting screws. Specification RF Locking Time: Less than 5 sec. Audio Locking Time: Less than 10sec. Test Equipment Connection Points CH-1: PB RF Envelope CH-2: Audio Output RF Envelope Output Point Audio Output Jack Test Conditions VCR(VCP) State Play an alignment tape (with 6H 3kHz Color Bar Signal) Checking Procedure Play an alignment tape then change the operating mode to CUE or REV and confirm if the unit meets the above listed specifications. NOTES: 1) CUE is fast forward mode (FF) 2) REV is the rewind mode (REW) 3) Referenced to the Play mode 9-2. Check the condition between the Audio and Video Sync. (Lip Sync.) Test Equipment/Fixture Oscilloscope Alignment Tape Specification Less than ±16.6msec Test Equipment Connection Points CH-1: PB RF Envelope CH-2: Audio Output RF Envelope Output Point Audio Output Jack Test Conditions VCR(VCP) State Play an alignment tape Checking Procedure 1) Confirm that the period (A) in Fig. C-9-1 is within ±16.6m/sec. 2) If the result is abnormal, repeat adjustment #7. (X-Value adjustment) 3) Check before starting repairs The following faults can be remedied by cleaning and oiling. Check the needed lubrication and the conditions of cleanliness in the unit. Check with the customer to find out how often the unit is used, and then determine that the unit is ready for in spection and maintenance. Check the following parts. Table 2
Phenomenon Poor S/N, no color Tape does not run or tape is slack Inspection Dirt on video head or worn video head Dirt on pinch roller, belt o flywheel belt

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10. Maintenance/Inspection Procedure 1) Required Maintenance VCR(VCP) is much The recording density of a higher than that of an audio tape recorder. VCR(VCP) components must be very precise, at tolerances of 1/1000mm, to ensure compatiblity with other VCRs. If any of these components are worn or dirty, the symptoms will be the same as if the part is defective. To ensure a good picture, periodic inspection and maintenance, including replacement of worn out parts and lubrication, is necessary. 2) Scheduled Maintenance Schedules for maintenance and inspection are not fixed because they vary greatly according to the way in which the customer uses the VCR(VCP), and the environment in which the VCR(VCP) is used.But, in general home use, a good picture will be maintained if inspection and maintenance is made every 1,000 hours. The table below shows the relation between time used and inspection period. Table 1 (Do not move the cleaning patch vertically. Make sure that only the buckskin on the cleaning patch comes into contact with the head. Otherwise, the head may be damaged.) Thoroughly dry the head. Then run the test tape. If Isopropyl Alcohol remains on the video head, the tape may be damaged when it comes into contact with the head surface. 2) Clean the tape transport system and drive system, etc, by wiping with a cleaning patch wetted with Isporopyl Alcohol. NOTE (1) It is the tape transport system which comes into contact with the running tape. The drive system consists of those parts which moves the tape. (2) Make sure that during cleaning you do not touch the tape transport system with the tip of a screwdriver and no that force is that would cause deforming or damage applied to the system.

8. 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 Oscilloscope Alignment tape Blank Tape Post Height Adjusting Driver Screw Driver(+) Type 5mm Test Equipment Connection Points CH-1: PB RF Envelope CH-2: NTSC: SW 30Hz PAL :SW25Hz Head Switching Output Test Point RF Envelope Output Test Point Test Conditions VCR(VCP) State Play the blank tape Play an alignment tape Adjustment Points Guide Roller Precise Adjustment Switching Point Tracking Preset X-Value Checking/Adjustment Procedure Play a blank tape and check for tape curling or creasing around the roller guide. If there is a problem then follow the procedure 5. �Guide Roller Height� and 6. �Audio Control(A/C) Head Adjustment�. Connection Diagram

5-2) Greasing 1) Greasing guidelines Apply grease, with a cleaning patch. Do not use excess grease. It may come into contact with the tape transport or drive system. Wipe any excess and clean with cleaning patch wetted in Isopropyl Alcohol. 2) Periodic greasing Grease specified locations every 5,000 hours.

7. X-Value Adjustment Purpose: To obtain compatibility with other VCR(VCP). Test Equipment/Fixture Oscilloscope Alignment tapes Screw Driver(+) Type 5mm Post Height Adjusting Driver Test Equipment Connection Point CH-1: PB RF Envelope CH-2: NTSC: SW 30Hz PAL :SW25Hz Head Switching Output Test Point RF Envelope Output Test Point Test Conditions VCR (VCP) State Play an alignment tape Adjustment diagrams

9-3. Check for tape curling or jamming Test Equipment/Fixture T-160 Tape T-120 Tape Specification Be sure there is no tape jamming or curling at the begining, middle or end of a T-160 tape. VCR (VCP) State Run the CUE, REV play mode at the beginning and the end of the tape. 9. Check the Tape Travel after Reassembling Deck Assembly. B. Confirm that the tape passes smoothly between the T/UP guide and the Pinch Roller (Using a mirror or the naked eye). 1) After completing step A. (Preliminary Adjustment), check that the tape passes around the T/ UP post without folding at the top or bottom. If folding is observed, due the following: (1) If folding is observed at the lower part of the T/UP post, then slowly turn the tilt adjustment in 9-1. Check Audio and RF Locking Time during playback and after CUE or REV (FF/ REW) Test Equipment/Fixture Oscilloscope Alignment tape (with 6H 3kHz Color Bar Signal) Stop Watch Checking Procedure 1) Confirm that the tape runs smoothly around the roller guides, drum and A/C head assemblies while abruptly changing operating modes from Play to CUE or REV. This is to be checked at the begining, middle and end sections of the cassette. 2) Confirm that the tape passes over the A/C head assembly as indicated by proper audio reproduction and proper tape counter performance.

Dirt on video head or in tape transport system Color beats Dirt on full-erase head Low volume or distorted audio Dirt on audio/control head No Fast forward or rewind or Dirt on belt rotation is slow

Vertical jitter, horizontal jitter

Waveform

4) Supplies Required for Inspection and Maintenance 1) Grease Kanto G-31 1 G or equivalent 2) Isopropyl Alcohol or equivalent 3) Cleaning Patches 5) Maintenance Procedure 5-1) Cleaning 1) Cleaning video head First use a cleaning tape. If the dirt on the head is too stubborn to remove by tape, use the cleaning patch. Coat the cleaning patch with Isopropyl Alcohol. Touch the cleaning patch to the head tip and gently turn the head(rotating cylinder) right and left.

Adjustment Procedure 1) Loosen the fixed mounting and X Value adjustment screw. 2) Allow the mechanism to run long enough for auto tracking to complete it�s cycle. 3) Move the A/C base laterally in the direction as shown in the diagram to find the center of the peak that allows for the maximum waveform