Compatibility Adjustment - Philips VR407/77 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 A/C 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, it is required to set the VCR
to the Jig RCU mode (the mode in which codes from
the Jig RCU can be received). (See SECTION 1 DISAS-
SEMBLY.)
Jig RCU
[Data transmitting method]
Depress the " " ( 3 ) button
after the data code is set.
CUSTOM CODE
43: A CODE
53: B CODE
DATA CODE
Fig. 2-3a Jig RCU
2.3.1 FM waveform linearity
•
Signal (A1) Alignment tape(SP, stairstep, PAL)
•
(A2) Alignment tape(LP, stairstep, PAL)
•
Mode (B) PB
•
Equipment (C) Oscilloscope
•
Measuring point (D) TP106 (PB. FM)
•
External trigger (E) TP111 (D.FF)
•
Adjustment part (F) Guide roller [Mechanism assembly]
•
Specified value (G) Flat V.PB FM waveform
•
Adjustment tool (H) Roller driver
(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) Set the VCR to the manual tracking mode.
(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 by the tracking opera-
tion. 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.)
(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
2-16
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