6-38
8. Check pin 9 (SWOUTA) for an active signal when one of the Auxiliary Front Panel buttons is
pressed (bezel, SELECT, STATUS, MENU OFF). Otherwise, a HI is being shifted out of serial shift
register U700. If the SWOUTA signal does not show a square pulse when one of the buttons is
pressed, troubleshoot U700.
7. Check pin 22 (AOUT2) for an active return signal from the Auxiliary Front Panel INTENSITY pot
and Front Panel BNC connectors. Individual signal voltage levels may be checked using the Front
Panel MUXTEST if the signal line is active. If switching levels are not present on the AOUT2 signal
line, troubleshoot s-to-t multiplexer U600.
6. If the SW/OUT signal line is active, the Switch Scanner circuitry is working. If it is not active,
troubleshoot t-ot-B decoder U903 and serial shift register U904 for correct operation.
5. Check pin 25 for active return signal from the Front-Panel Switches.
4. If the return signal line is active, go to Step 5. If it is not active, showing the different voltage lev-
els from the Front Panel pots, troubleshoot Front Panel Pot Scanner U902 (an B-to-t multiplexer).
Problems with a single pot output rather that a total failure of the Pot Scanner may be checked
out using the MUXTEST mentioned in Step 2.
3. Check pin 24 for active AOUTOreturn signal from the Front Panel pots.
2. If the signals checked in Step 1 are active, go to Step 3. If these signals are not actively switching,
perform the Front Panel MUXTEST to check that the J.lPdrives the MUXSEL signal lines in a tight
looping routine. In the MUXTEST, only the MUXSEL signal output lines are being driven. No out-
put will be seen on the
s7[
or SHCLK lines (pins 29 and 30 respectively).
1. Check pins 26, 27, 28, 29, 30, and 15 for active output signal switching. These signals are all
asynchronous, so a stable display pattern is not possible (without going to SAVE mode on the test
scope).
NOTE
Whenprobing around the Front PanelII-Pcircuitry, it is possible to cause bad data to
be
written to the SystemII-Pand/or the Front PanelII-Pby inadvertent grounding of pins or
accidental shorting of pins together.
If
this should occur, many trouble symptoms may be
present. To cure these symptoms, turn off the 2430 and turn it back on again. This
rewrites all RAM space in the System and Front Panel microprocessors with correct
operatingdata.
On the Front Panel J.lP(U700), do the following checks:
If there is a front panel problem and the Extended Diagnostics have not detected anything, the prob-
lem is not in the Front Panel Processor or its handshake logic with the System J.lP.
Front Panel and Auxiliary Front Panel (schematic diagrams 4 and 6):FRONT PANEL
PROBLEMS
3. If the LEDs do not follow the above pattern, troubleshoot bidirectional buffer U532 or U630
(assuming the LEDs do the 0 through 7 binary count during REG test section of EXT DIAG).
2. If the LEDs follow the above, GPIB IC U630 is at least responding to the System J.lP,and the
problem is probably in GPIB Bus Buffers U720 or U624.
1. Press the OUTPUT menu button, then SETUP, then MODE. Select LJONLY and see if the ADDR
LED is on. Select T/L and see if the ADDR LED is off. Select T/ONLY and see if the ADDR again
is on.
GPIB Test for Activity (schematic diagram 20):
GPIB
Table 6-6 (cont)
Maintenance-2430 Service
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