WORK INSTRUCTION
Testing of IC 30
1.
Perform physical inspection ( Visual Inspection stage )
1.1
Check :
•
All screws for tightness ( esp. H/S & IC fixing).
•
Capacitors for polarity.
•
Earth connection for good contact (XLR gnd to AC earth), including earthing of
RCA’s,
•
All wiring points for good contacts (Soldering and Crimping)
2.
Set up amplifier for test (Pre (PCB testing) ).
2.1
Connect amplifier to :
•
Variac (0 Vac)
•
Signal generator (Mic 1, no signal),
•
Resistive load (4ohm on 4ohm output).
2.2
Reset controls :
•
Volume controls to minimum,
•
Bass/treble control to center,
•
Phantom power switch to off,
3.
Power up (Pre (PCB testing).
3.1
Turn on power switch and adjust voltage to 230VAC. Watch current meter for
excess current draw.
3.2
Check DC power supply at fuse. Should be approximately. 7V ( + 1V )
3.3
Check DC voltage on mixer board. Should be approximately. 6V (Check on 8 No.
Pin of 1458).
3.4
Adjust variac to 240VAC. Check DC power supply. Should be approx. 15V
(+ 1V) loaded, no load (16.5V + 1V).
3.5
Check DC voltage on mixer board. Should be approx. (11V + 1V).
4.
AC Check (Final stage).
4.1
Set signal generator to (1mV) + 0.2mV. Turn up Mic1 volume control to full.
Watch for irregularities with output. Check sensitivity of input. – MIC 1mV
(+ 0.2mV) in 10.5Vrms out (2.6% THD).
4.2
Measure 100V line, 70V line, tol. 5%
4.3
Check tape output (0.4V + 100mV).
4.4
Check Bass control @100HZ = + 12dB (can get only upto 8V O/P with total swing
of (20 – 24dB) ) and treble @10KHz = + 10dB (tolerance. 10%) total swing (18 –
22dB).
