HP 3562A Service Manual page 489

MO D E L 3S62A
8-7 A3 PRO(iRAM ROM
The i nformation in this section shou ld be used to isolate fau lty su bblocks on the A3 Program
ROM assemb ly. A l l proced u res assu m e that the Fault Isolation proced u res of Section V I I
were used to determ ine that this board has fai led and that the C i rc u it Descriptions of
Section VI are u nderstood.
Service procedures described in this section are performed with
protective co vers removed and power applied. Hazardous voltages
in these circuits can cause personal injury if contacted.
Do not insert or remo ve a n y circuit board in the HP 3562A while
power is on. Power transients caused b y insertion or removal m a y
damage the circuit boards.
How to Use This Section
Ref.erence
Afh�r-Repair
Troubleshooting Hint
The ROM board is very sensitive to changes in + 5 V. Check this voltage before proceed ing
with the rest of this section.
A. IProgram ROM Diagnostics
The PROG ROM test ru ns at turn-on. Table A3-1 l i sts and explains the A2 L E D annunciations
of test fai l u res. The test seq uence fol lows:
1 . Verifies system bus. This is done by echoing data from the FFT board. I f the FFT board
is not prese nt, the system bus can not be verified.
2. Verifies ROM bus. The system C P U reads the contents of two locations i n the lowest
ROM pair and verifies that they are correct. One n u m ber is the com p lement of the
other so that a l l ROM bus l ines are togg led. If this test fa i l s, the L E D a n n u n c iations
also i n d icate whether the system bus was ve rified.
WARNING
CA UTION
Start tro u b l eshooting with part A, P rogram ROM D i agnostics.
Refer to Section IX for the component locators and sc hematics. refer
to figu re 4-1 in Section IV for location of cab les and boards.
Use tab le A3-3 to determine which adju stm ents and tests need to be
performed to com p l ete i n stru ment service.
S E RV I C E
8-39