JVC HR-D540EE - Page 24

1.5
MAIN
PARTS
REMOVAL
AND
REPLACEMENT
Item
7
Checkpoints
Upper drum assembly
¢Symptoms: FM signal absent,
intermittent or weak on one ch-
annel; large difference in channel
output levels
Cause: Worn or damaged video
heads, poor response, etc.
SP CH-1
Fig. 1-5-1
DRUM TOP VIEW
Adjust
Roller driver
PTU94002
Hex driver
+
Fig. 1-5-4 S.T. Pole base
——
| Adjustment and Checks
Mounting direction
See Fig. 1-5-1.
(Symptom: no picture)
Fig. 1-5-2 Drum Position
After replacing, observe that upper drum hole
A is opposite the motor axis from lower drum
hole B.
Axis wobble
See Fig. 1-5-2.
(Symptom: jitter, poor FM
linearity)
PB FM: Main board TP206
DRUM FF: Main board TP411
FM linearity check
See Fig. 1-5-5.
picture noise)
PB FM: Main board TP206
FF: Main board TP411
Fig. 1-5-5 FM linearity
b.0.7,22065,22 0.65
a a a
(Symptom: vertical sync absent, U
—
Record and playback in SP mode.
Confirm absence of large difference between
channels. (Fig. 1-5-3)
“] Fig. 1-5-6 $.T. Pole base position
1) Play stairstep signal of the MH-2 Alignment
Tape. Confirm absence of obvious FM wave-
form loss and that operating the Tracking
yields the optimum point.
2) Refer to Fig. 1-5-4, adjust for loss at the le ft
edge (drum entry) of the FM waveform by
turning the guide roller of the supply pole
base. Similarly, adjust for loss at the right
edge (drum exit) by turning the guide roller
of the take-up pole base.
Note: If FM loss occurs on both channels ard
cannot be corrected by adjusting tbe
guide rollers, the lower drum needs
replacement.