6-76
1. Select the 1/2 TRIG POSITION and set the Sec/Div setting to 1 ms on the test scope. Check for
the FPDNRD clock pulse to U861 at pin 3 (leads the trigger strobe rising edge about 120 JLs).If
missing, replace U70D.
4500 A13U700 pin 13 (FPDNRD):
2. Display REF1 and probe U751 pin 18, 16, 14, and 12. These should all be LO during the time
U751 is enabled. If not LO, it indicates either a problem in U700 or an invalid DC voltage level at
one of the U700 inputs. If one of these four diagnostic bits is HI and the supply pins, etc., are ok,
replace U700.
1. Check that the enable pulse to U751 (pins 1 and 19) is present and save to REF1. If not present,
check for an open between U862A pin 1 and U751 pins 1 and 19.
4400 DIAG BYTE A13U700:
If the 4 MHz clock is missing, troubleshoot the clock source. Restore the prior test scope setup as
for test 2110 (a good use for RECALL SETUP if using a 2430 as the test scope.)
1. Check that U861 pin 9 has a HI pulse.
If
not, select 50 ms/div and ENVELOPE acquisition mode
on the test scope; then, run test 4000 for the scope under test. At pin 12 of U700, check for a
strobe occurring near the falling edge of the trigger strobe. If the strobe is ok, replace U861. If
missing, test for 4 MHz at U700 pin 5 and replace U700 if the 4 MHz clock is ok.
4300 A13U700 pin 12 (WR TO HOST):
2. Check U861 pin 6 for a LO-to-HI transition from the strobe at U861 pin 1. If occurring, replace
U861.
1. Check U861 pin 1 for a negative strobe during the HI period of the trigger strobe. If not present,
replace U862.
4200 A13U861 pin 6 (FPDNRD):
2. Check U861 pin 9 for a HI-to-LO transition. If not occurring, replace U861.
1. Check U862 pin 1 for 0.2
JLS
negative strobe during the HI period of the trigger strobe. If not
present, replace U862.
4100 A13U861 pin 9 (FPINT):
Run tests 4100 through 4600 in CONTINUOUS mode. Use the CH 2 probe for the following checks
while the specific test is selected and running.
Set up the 2430 test scope as in Step 1 of the 2110 troubleshooting procedure.
NOTE
Since the Front Panel pP is being reset in this test, there is no way to HALT if one
chooses a CONTINUOUS loop mode and runs the tests from the front panel. However, to
allow access to these features for any possible troubleshooting, looping has not been dis-
abled. ONCE
A
TEST IS INVOKED IN CONTINUOUS MODE,
A
POWER OFF/ON CYCLE
MUST BE USED TO EXIT FROM THE FRONT PANEL. Via the GPIB, the tests may be
started and halted by sending the appropriate commands.
Table
6-6
(cont)
Maintenance-2430 Service
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