Teac A-400 - Monitor Performance; Specified Input Level Setting; Minimum Input Level Checks; Level Meter Calibration

4-1. MONITOR PERFORMANCE
NOTE
Place DOLBY NR switch to OUT position for this monitor
circuit alignment procedure.
4-1-1. Specified Input Level Setting
1. Connect an AF oscillator to the LINE IN jacks, through an
attenuator.
2. Connect a VTVM_ between the T.P. (test points) for
VR102/VR202 and ground on the REC/PB amplifier PC
board.
Load a TEAC MTT-505 test tape (blank) on the deck.
Adjust for -25dB on VTVM
(Specified RECORD control setting}
VTVM
—25dB(43.5mv)
OSCILLATOR
Place the deck in the PAUSE mode.
Apply a 400 Hz signal/—9 dB (274 mV) to the LINE IN jacks.
Turn the RECORD controls to obtain the reading of —25 dB
(43.5 mV) on the VTVM. Note the position of the RECORD
control as this is the specified RECORD control setting
referred to in subsequent procedures.
7. Connect the VTVM between the Dolby T.P. (test points) and
the ground on the REC/PB amplifier PC board.
8. Adjust VR102/VR202 to obtain 580 mV (2.5 dB).
oO or oo
4-1-2. Minimum Input Level Checks
9. Turn the RECORD controls fully clockwise.
10. Apply a 400 Hz test tone at minimum input level as listed
below to each input jack.
11. Check for (the specified value of) 580 mV (-2.5 dB) at the
Dolby test points using the VTVM.
INPUT Switch
Position
Input Jacks Minimum Input Level
19 dB +3 dB (61.5 mV ~ 122 mV)
-67 dB +3 dB (0.244niV~0.488mV)
-35 dB +3 dB (9.75 mV ~ 19.4 mV)
LINE IN LINE
Mic MIC/DIN
DIN MIC/DIN
4-1-3. Level Meter Calibration
“12. Set the INPUT Switch to the LINE position.
13. Set the AF oscillator for 400 Hz at —9 dB (274 mV) and set
RECORD controls to specified level. (same as set in 4-1-1)
14. Adjust VR103/VR203 for +3 VU (marked'with “O0”) on
the level meter on the deck.
VTVM
—2.5dB (580mv)
OSCILLATOR
OodoLey TP |
400Hz
ATTENUATOR
RECORD}: Max. Position
Minimum Input Level
DECK under TEST
(PAUSE mode) .
Fig. 27 Test Condition for Minimum Input Level Checks
T~398
14 NOTE:
TP.
(for
VRioz/VR202)
POOLBY
TRI
400Hz
ATTENUATOR
VRio2/VR202,
DECK under TEST
(PAUSE made)
i)
Adjust for -2.5dB on VTVM
VTVM
-2.5dB (S80mv)
OSCILLATOR
vRioz/VReoz
DECK under TEST
(PAUSE mode) T397
Fig.
26
Test
Condition
for
Specified
Input
Level
Setting
OSCILLATOR
Adjust
for
+3VU
on
Level
Meter
VRi03/VR203 + 3vu
LEVEL METER |
RECORD control : Specified Setting
DECK under TEST
{PAUSE mode) TOROS
Fig.
28
Test
Condition
for
Level
Meter
Calibration
400Hr
ATTENUATOR
For actual adjustment/test point locations, see page 21.