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Signal Input Assembly Trouble-shooting
EON Power10
A) Initial Setup
Connect board under test to a +/– 15V power supply at the designated connector pins.
Connect Porta-one Generator (or a function generator) output A to XLR input connector.
B) "Mic" LED Test
Turn Generator A off. Place Mic/Line switch, S1 in "Mic" position, power up board and
verify that "Mic" LED, D6, lights. If the voltage across D6 is greater tan 3V, replace LED.
If LED doesn't light check power supply (see "C" below) and check IC, U2.
C) Power Supply Test
Verify that +15V and –15V supplies are at the correct levels.
Check for shorts from +15V to ground, –15V to ground, and +15V to –15V. Check for opens
on +15V and –15V lines. Verify that D1 - D4 are not shorted.
D) Line Amp Gain Test
1) Place Mic/Line switch. SW1, in "Line" mode (switch out), set generator level at 1V P/P at
XLR input connector. Adjust volume control, R25, fully clockwise, set frequency to 400Hz.
2) Verify that voltage at output, pin 1 of J1 = 800mV P/P (+/– 100mV).
3) Verify presence of 400mV P/P (+/– 50mV) at pin 1 of U1.
4) Remove oscillator connection to XLR input. Verify resistance from pin 2 of J2 to pin 3 of
U1 = Pin 3 of J2 to pin 3 of U1 = 24.23K. If not, check for shorted sections of SW1. Verify
resistance from pin 2 to pin 1 of U1 = pin 3 of U1 to ground = 10K. If not check for opens and
shorts around U1.
5) Rotate Volume control counter clockwise while monitoring pin 2 (see schematic) of R25.
Voltage should gradually decrease to zero. If the level is intermittent or control does not
attenuate, replace defective potentiometer R25.
E) Line Amp Frequency Response Test
Advance volume fully clockwise and adjust for 800mV P/P at pin 1 of J1. Change Fre-
quency to 20kHz and verify a level of 750mV (+/– 100mV). Change frequency to 20Hz and
verify a level of 750mV (+/– 100mV).
F) Mic Amp Gain Test
Push Mic/Line switch, SW1, in. Set volume control, R25 fully clockwise. Adjust for 20V P/P
at pin 1 of J1. The input level to the board should be 20mV P/P (+/– 1mV). Verify that voltage
at pin 1 of U1 is equal to 150mV P/P (+/– 20mV).
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