Technics RS-M226 - Page 6

RS-M226
ITEM MEASUREMENT & ADJUSTMENT
Set the tape selector to Normal, and load the test tape (QZZCRA)
Adjust the attenuator to reduce the input signal level by 20dB
Adjust the AF oscillator to generate 50Hz, 100 Hz, 200Hz, 500Hz, 1 kHz, 4kHz, 8kHz and 10 kHz
(ooo
signals, and record these signals on the test tape
Playback the signals recorded in step 6, and check if the frequency response curve is within the limits
shown in the overall frequency response chart for normal tapes (fig. 11).
(If the curve is within the charted specifications, proceed to steps 8, 9 and 10.)
If the curve is not within the charted specifications, adjust as follows,
Adjustment (A):
When the curve exceeds the overall frequency
response chart specifications (fig. 11) as shown
in fig 13.
fe ee +6dB
+
one = t ct —4dB
—t—4—f ett 608
rae
1 — gap
VkH2 2kHz 4kHz 8kHz1OkHz
Fig. 13
1) Increase bias current by turning VR9
(L-CH) and VR10 (R-CH).
(See fig. 1 on page 3.)
Repeat steps 6 and 7 to confirm
NO
(Proceed to steps 8. 9 and 10 if the curve
1S now within the charted specifications in
fig. 11.)
3) If the curve still exceeds the specifications
(tig. 11), increase bias current further and
repeat steps 6 and 7
8. Switch the tape selector to CrO:.
change test tape to QZZCRX, and
record 50Hz. 100Hz. 200 Hz,
500Hz, 1 kHz, 4kHz, 8kHz, 10kHz
and 12.5 kHz signals
the signals and check if the curve is
within the limits shown in the overall
frequency response chart for CrO»
tapes (fig. 15).
9. Switch the tape selector to Metal.
change test tape to QZZCRZ, and
Then, playback
Adjustment ‘B):
When the curve falls below the overall frequency
response chart specifications (fig 11) as shown
in fig. 14,
4 Ti+ 408
re) ttt + 208
> HOB
3 —150B
Toy ~ 208
i = H 4dB
Pree teed +t tt eae
roy | 8 dB
LkH2 2kHz 4kHz 8kHz10kHz
as, |
oe i +4 54B
Fig. 14
1) Reduce bias current by turning VR9 (L-CH)
and VR10 (R-CH).
2) Repeat steps 6 and 7 to contirm
(Proceed to steps 8. 9 and 10 if the curve is
now within the charted specifications in fig
11)
3) If the curve still falls below the charted
specifications (tig. 11), reduce bias current
further and repeat steps 6 and 7
50Hz 100Hz 200Hz
Overall frequency response chart (CrO2, Metal)
PTT
1kHz 2kHZ 4kHz uly
\12.5 KHz
kHz
0
Fig. 15
record 50Hz. 100Hz, 200Hz, 500Hz. 1 kHz, 4kHz, 8kHz, 1OKHz and 12.5 kHz signals
playback the signals and check if the curve 1s within the limits shown in the overall frequency response
chart for metal tapes (tig. 15).
positions.
* Read voltage on VTVM and caiculate bias current by following formula:
Bias current (A) =
Value read on VTVM (V)
10 (Q)
Then,
10. Confirm that bias currents are approximately as follows when the tape selector is set at different
around 350A (Normal position)
around 450zA (Cr02 position)
around 700A (Metal position)
\ measured at TP1 (L-CH) and TP2 (R-CH)
@® Overall gain
Condition :
+ Record/playback mode
* Tape selector
seanee Normal position
* Input level controls --- MAX
* Standard input level;
MIC «+--+ —72+4dB
LINE IN--- —-24+4dB
Vv
position.
ATT to LINE IN.
A
0.45V.
Using test tape, make recording.
P
OUT on VTVM becomes 0.45V.
Test equipment connection is shown in fig. 16.
ace UNIT into record mode, and tape selector to normal
Supply 1 kHz signal (—24 dB) from AF oscillator, through
djust ATT until monitor level at LINE OUT becomes
layback recorded tape, and make sure the value at LINE
AF oscillator
LINE IN
Record/playback
head
Test tape
Fig. 16
Record mode
Test tape
Playback
mode
ytym
Oscilloscope