Shure AUDIOMASTER 1200, Service Manual

Page: 13 / 30

To check LEDs, connect the cathode (notch or flat on flange,
tab on lead or short lead) of the LED to the negative terminal of a
standard 9 V transistor battery. Connect the positive battery
terminal through a 4.7 k resistor to the LED anode. Replace any
LED that does not light.
CAUTION
Do not check LEDs with an ohmmeter. The LEDs may be
damaged or erroneous readings may be obtained.
To check transistors, the ohmmeter should be set to the 100-
or 1,000-ohm scale. Transistors must be removed from the
circuit before testing. If all conditions in the following table are
met, the transistor may be considered free of any major defect;
if any of the following conditions are not met, the transistor
should be replaced. See Figure 3 for active component lead
codes.
OHMMETER CONNECTlON
OHMMETER READING
“Plus” Lead
NPN PNP
“Minus” Lead Transistor Transistor
Collector Emitter High High
Emitter Collector High High
Collector
Base High Low
Emitter Base High Low
Base Collector Low High
Base Emitter Low High
FERRITE BEADS
All low-impedance microphone connectors contain ferrite
beads (L101-L112, SHR-01). Be sure to replace any ferrite
beads removed during servicing.
SERVICE ILLUSTRATIONS
Immediately following the parts list on the pages that follow
are printed wiring board foil and legend drawings, and circuit
diagrams. Once a board has been located through the parts
location photo (Figure 1), the components on that board can be
located from the board drawing. The function of the part is
shown on the relevant circuit diagram.
OPTIONAL ACCESSORIES
The following optional accessories are designed for use with
the Shure 1200 AUDIOMASTER Powermixer.
Carrying Case . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A1200C
Input Expansion Module (2 channels,
2 each HI Z and LO Z inputs . . . . . . . . . . . . . . . . A1200MX*
Speaker Cable, 15 m (50 ft), with phone plugs . . . . . . A50SC
240 V Conversion Kit . . . . . . . . . . . . . . . . . . . . . . . . . RKC209*
Line Matching Transformer (LO Z to HI Z) . . . . . . . . . . . A95UF
Phono Preamplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M64A
*For installation by qualified service personnel only.
9