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Compatibility Adjustment; Checking/adjustment Of Fm Waveform Linearity - JVC HR-J271MS Service Manual

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2.3 COMPATIBILITY ADJUSTMENT

Notes:
• Although compatibility adjustment is very important,
it is not necessary to perform this as part of the nor-
mal servicing work. It will be required when you have
replaced the audio control head, drum assembly or any
part of the tape transport system.
• To avoid any damage to the alignment tape while per-
forming the compatibility adjustment, get a separate
cassette tape (for recording and play back) ready to
be used for checking the initial tape running behavior.
• Unless otherwise specified, all measuring points and
adjustment parts are located on the Main board.
• When using the Jig RCU, set its custom code to match
the custom code of the VCR.
Jig RCU
[Data transmitting method]
Depress the "
after the data code is set.

2.3.1 Checking/Adjustment of FM Waveform Linearity

Signal
Mode
Equipment
Measuring point
External trigger
Adjustment part
Specified value
Adjustment tool
(1) Play back the alignment tape (A1).
(2) Apply the external trigger signal to D.FF (E), to observe
the V.PB FM waveform at the measuring point (D).
(3) Press the channel buttons (+, –) simultaneously to enter
the manual tracking mode. This also brings tracking to
the center (centre).
(4) Make sure that there is no significant level drop of the
V.PB FM waveform caused by the tracking operation, with
its generally parallel and linear variation ensured. Per-
form the following adjustments when required. (See Fig.
2-3-1a.)
(5) Reduce the V.PB FM waveform while pressing the chan-
nel buttons (+, –) during playback. If a drop in level is
found on the left side, turn the guide roller of the pole
base assembly (supply side) with the roller driver to make
the V.PB FM waveform linear.
If a drop in level is on the right side, likewise turn the guide
roller of the pole base assembly (take-up side) with the
roller driver to make it linear. (See Fig. 2-3-1c.)
" ( 3 ) button
CUSTOM CODE
43: A
CODE
53: B
CODE
DATA CODE
Fig. 2-3a Jig RCU [PTU94023B]
(A1)
Alignment tape(SP, stairstep, PAL) [MHPE]
(A2)
Alignment tape(LP, stairstep, PAL) [MHPE-L]
(B)
PB
(C)
Oscilloscope
(D)
TP106 (PB. FM)
(E)
TP111 (D.FF)
(F)
Guide roller [Mechanism assembly]
(G)
Flat V.PB FM waveform
(H)
Roller driver [PTU94002]
Digitized in Heiloo Netherlands
(6) Make sure that the V.PB FM waveform varies in parallel
and linearly with the tracking operation again. When re-
quired, perform fine-adjustment of the guide roller of the
pole base assembly (supply or take-up side).
(7) Unload the cassette tape once, play back the alignment
tape (A1) again and confirm the V.PB FM waveform.
(8) After adjustment, confirm that the tape wrinkling does not
occur at the roller upper or lower limits. (See Fig. 2-3-
1d.)
[Perform adjustment step (9) only for the models
equipped with SP mode and EP (or LP) mode.]
(9) Repeat steps (1) to (8) by using the alignment tape (A2).
INITIAL MODE
Max level
Min level
Proper waveform variation
Improper waveform variation
Fig. 2-3-1a
Roller driver
Guide roller (supply side)
Fig. 2-3-1b
1/21/2018
2-16

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