Lexicon LXP-5 Service Manual

LXP-5 Service Manual
Performance
Verification
1 . Set oscilloscope for 2.5v/div (w/XIO probe) and a 1 mSec/div time base.
2 . Connect scope probe to U1 pin 4.
3. Vary the Variac output level between 104VAC to 125VAC while monitor¬
ing U1 pin 4 on oscilloscope. This level should remain in a logical high
condition (+5V).
4. Continue to monitor U1 pin 4 with oscilloscope and slowly reduce Variac
output to 85 VAC. Pin 4 signal level should go to a logical low condition when
the Variac output passes through the 100 - 85VAC range, if this test fails,
make certain that transformer AC output (across C25) is between 9.0-
11 .OVAC with 120VAC input. If AC transformer is OK, suspect LXP-5 power
down reset circuitry failure.
5. Return Variac to 120 VAC.
Using the frequency counter, measure the clock frequencies at the following
points:
Signal Name
Location
Meas
Tolerance
ZCLK
U4 /pin 6 4MHz
±0.5%{3980000-4020000 Hz)
MIDICLK
U3 /pin 9 500kHz
±0.5% (497500 -502500 Hz)
Brown Out / Power Down
Test
Clock Measurements

Lexicon LXP-5 Specifications

General

Brand	Lexicon
Model	LXP-5
Category	Recording Equipment
Language	English