Teac A-650 - Tape Efficiency Tests; Erase Efficiency Measurement

6-4-9. ERASE EFFICIENCY
Specification: 65 dB (minimum) Preparations:
SPKR AMP
OSCILLATOR
VTVM
IkHz FILTER
O O
o
1.
Connection
Fig. 6-18
2.
Switch Setting:
3.
DOLBY NR
LIMITER
BIAS
EQ
OUT OUT
OUT
1
1
4.
5.
6.
(I)
R
rewind
7.
(2)
(3)
rewind
(4) R
(5)
Erased
r I Signal
T-465
Erase Efficiency Check Procedure
Fig. 6-19
30
R
L
3
I
A
LINE:
MIC:
DECK
under TEST
]R
U
□ R
~l L
NOTE
To measure erase efficiency, a 1 kHz
narrow bandpass Biter should be used.
The test signal delivered from the AF
oscillator should be tuned to the filter
used.
OSCILLOSCOP E
o
(( J) o
play and compare
_____ £
OUTPV'
IL I
L 'V,
ATTENUATOR
erased
5
Control Setting.
OUTPUT: Specified Setting (See 6-2-2)
Specified Setting (See 6-3-2)
Minimum Setting
record
Load
tape.
Apply and record a 1 kHz signal
at +1 dB (0.869 V) for several
seconds ....................................... (I)
Rewind the tape to the mid-point
of the recording and remove the
signal from the LINE IN jacks.
(2)
Place the deck in the record mode
and record through this previously
recorded portion with no input
signal applied ............................. (3)
Rewind the tape to the starting
point of the 1 kHz signal recorded
portion ....................................... (4)
Play the tape and read the indica 
tion on the VTVM to obtain the
output level of both the unerased
portion and the erased portion of
the recorded section ............... (5)
Measure the output level differ 
ences between the 2 portions.
Numbers in parentheses correspond to
steps in Fig. 6-19.
a TEAC MTT-505B test