Shure M367 Serie Guia Del Usuario página 8

WARNING
Only qualified service technicians
should perform these modifications.
Perform all modifications through solder points accessible on the
main PC board.
DISASSEMBLING THE M367
1.Remove the mixer top cover as previously described.
2.Carefully remove three multi–pin cable assembly connectors
from upper front PC board (nearest front panel). Remove the
three Phillips head screws securing the PC board. Remove up-
per front PC board.
3.Carefully remove four multi–pin cable assembly connectors from
upper rear PC board (nearest rear panel). Remove the three
Phillips head screws securing the PC board. Remove upper rear
PC board.
4.Perform modification (refer to appropriate following procedure).
Note that all modifications can be performed without removing
the main PC board.
5.Reassemble M367 by performing above steps in reverse, as-
sembling the Phillips screws in the order indicated on the upper
front and upper rear PC boards.
CHANGING OPERATOR VOLTAGE RANGE
The M367 and M367E can be internally modified for an alternate
operating range.
M367 Operation at 220–240 Vac:
Disconnect the ac power and remove the mixer top cover as de-
scribed above. Locate Voltage Selector switch S301 adjacent to
power transformer T301. Use a screwdriver to move the center dial
so "230" is opposite the indicator. Replace the top cover. Open the
rear–panel fuse compartment and replace the 0.125 mA, 250 V
fuses (operating and spare) with 0.063 mA, 250 V fuses of the
same size and type. Close the fuse compartment.
For M367E Operation at 100–120 Vac:
Follow the first two steps from the M367 Operation at 220–240
Vac instructions. Open the rear–panel fuse compartment and re-
place the 0.063 mA, 250 V fuses (operating and spare) with 0.125
mA, 250 V fuses of the same size and type. Close the fuse compart-
ment.
CHANGING LINE LEVEL OUTPUT IMPEDANCE TO
600 W
Locate resistor R621 (near IC U602 pin 8) on the main PC board
and remove it. Locate empty pads X621 (near resistor R621). Sol-
der a 430 Ω,
1
/ W resistor through the holes at X621.
2
CHANGING UNSWITCHED LINE OUTPUT TO MIC
LEVEL
Locate resistor R632 (near output transformer T601) and re-
move. Locate empty pads X632 (near transformer T601). Solder a
jumper wire through the holes of X632.
CHANGING MIXER AUDIO LEVELS IN HEADPHONES
(Pull/Monitor Switch Activated, DIP Switch S701
Position 4 Closed)
Locate empty pads X649 (near Phones potentiometer R648).
1
Solder a 68 kΩ, / W resistor through the holes at X649 to hear pro-
4
gram audio 12 dB down from standard headphones level with Pull/
Monitor switch on (pulled out). Solder a 24 kΩ,
8
INTERNAL MODIFIABLE FUNCTIONS
1
/ W resistor
4
through the holes at X649 to hear program audio 6 dB from stan-
dard headphones level with Pull/Monitor switch on (pulled out).
CHANGING LOW–CUT FILTER CORNER FREQUENCY
(3 dB down point)
To decrease corner frequency:
1.Calculate new capacitor value for lower low–cut corner frequen-
cy. Use the following formula:
C in µF= (85/frequency) – 0.33
Example: for 200 Hz corner frequency,
85/200 ≈ 0.43
0.43 – 0.33 = 0.1
For 200 Hz corner frequency, use a 0.1 µF capacitor.
Note: Capacitor must be non–polarized; ceramic or film type;
16V rating or higher.
2.Locate the following empty pads:
Pad Channel
X421 1
X431 2
X441 3
Find all pads near ribbon cable assemblies W811, W812 and
W813.
3.Solder a new capacitor through the holes of the empty pads for
each channel to be modified.
To increase corner frequency:
Note: Low–cut corner frequencies much higher than the factory
preset of 260 Hz may excessively attenuate desired low– to mid–
frequency program material.
1.Locate the following capacitors near empty pads:
Capacitor Pad Channel
C425 X421 1
C435 X431 2
C445 X441 3
2.Remove the indicated capacitor for each channel to be modified.
3.Calculate new capacitor value for higher high–cut corner fre-
quency. Use the following formula:
C in µF= (85/frequency)
Example: for 400 Hz corner frequency,
C = (85/400) = 0.21
For 400 Hz corner frequency, use a 0.22 µF capacitor.
4.Solder a new capacitor through the holes of the empty pads for
each channel to be modified.
SLOWING OUTPUT METER FROM "True VU"
BALLISTICS
Locate empty pads X691 (at left of VU meter M1). Solder a 100
µF x 6.3 V electrolytic capacitor through the holes of X691. Observe
capacitor polarity as marked on the PC board. The response time
is now 500 ms with no overshoot. To further slow the meter re-
sponse, use a larger capacitor value.
CHANGING MIC LEVEL OUTPUT IMPEDANCE
Locate resistor R631 (near output transformer T601) and re-
move it. Locate empty pads X631 (near T601). Solder desired val-
1
ue / W resistor through the holes of X631. For example, use a 150
4
Ω, W resistor for 150 Ω output impedance.
1
/
4
Pad Channel
X451 4
X521 5
X531 6
Capacitor Pad Channel
C455 X451 4
C525 X521 5
C535 X531 6