Shure M367 important safety instructions Internal Modifiable Functions

INTERNAL MODIFIABLE FUNCTIONS

NOTE

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 proce- dure). Note that all modifications can be performed without removing the main PC board.

5.Reassemble M367 by performing above steps in reverse, assembling the Phillips screws in the order indicated on the upper front and upper rear PC boards.

CHANGING LINE LEVEL OUTPUT IMPEDANCE TO 600 Ω

Locate resistor R621 (near IC U602 pin 8) on the main PC board and remove it. Locate empty pads X621 (near resistor R621). Solder a 430 Ω, 1/2 W resistor through the holes at X621.

CHANGING UNSWITCHED LINE OUTPUT TO MIC LEVEL

Locate resistor R632 (near output transformer T601) and remove. 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). Solder a 68 kΩ, 1/4 W resistor through the holes at X649 to hear program audio 12 dB down from standard headphones level with Pull/ Monitor switch on (pulled out). Solder a 24 kΩ, 1/4 W resistor through the holes at X649 to hear program audio 6 dB from standard 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 frequency. Use the following formula:

Cin μF= (85/frequency) - 0.33

Example: for 200 Hz corner frequency,

85/200 9 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.

Pad	Channel	Pad	Channel
X421	1	X451	4
X431	2	X521	5
X441	3	X531	6

2. Locate the following empty pads:

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	Capacitor	Pad	Channel
	C425	X421	1	C455	X451	4
	C435	X431	2	C525	X521	5
	C445	X441	3	C535	X531	6
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. Ob- serve capacitor polarity as marked on the PC board. The response time is now 500 ms with no overshoot. To further slow the meter response, use a larger capacitor value.

CHANGING MIC LEVEL OUTPUT IMPEDANCE

Locate resistor R631 (near output transformer T601) and remove it. Locate empty pads X631 (near T601). Solder desired value 1/4 W resistor through the holes of X631. For example, use a 150 Ω, 1/4 W resistor for 150 Ω output impedance.

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