HP 3562A Service Manual page 537

MOD E L 3S62A
8-1 1 AS, GLOBAL RAM/DISPLAY CONTROLLER
A 1 7, DISPLAY INTERfACE
The i nformation in this section shou ld be used to isolate fau lty s u b b l ocks on the global
RAM and disp lay interface boards. A l l procedu res assume that the fau lt iso lation procedu res
i n section V I I have been used to determ ine that one of these boards has failed and that
the circ u it descriptions i n Section V I are u nderstood .
Service procedures described in this section are performed with
protective co vers remo ved and power applied. Hazardous voltages
in these circu its can cause personal injury if con tacted.
Do not insert or remove an y c ircu it board in the HP 3562A wh ile
power is on. Power transients caused by insertion or removal m a y
cause da mage to circu its o n the board being cha nged o r o n other
boards.
How to use this section
Start
Relerence
After-Repai r
Trclubleshooting Hints
1 . G lobal RAM or Display I nterface prob lems can blank or garble the d isp lay. The fol low­
ing featu res s i m p l ify fau l t isolation when the d i s p l ay is not functio n i ng p roperly:
a. Some d i agnostic resu lts are a n n u n c i ated on the A2 L E Ds as we l l as on the 1 345A
d is p l ay. Table A8-1 exp l ains the A2 L E D fau lt codes.
b. The A2 L E Ds w i l l d i s p l ay 87 when the power-up tests and cal i bration are f i n ished.
If this does not occur, refer to section V I I , Fault I so l ation.
2. The LED at the top of the A8 board (C R1 ) i n d i c ates RFD on the system bus. It is not
used to service the A8 board.
WA RNING
CA UTION
Start troub leshooting with part A, G l obal RAM Di agnostics. U se of
this section w i l l i s o l ate the problem to a s u b b l ock of A8 or A1 7.
Refer to Section IX for the com ponent locators and schematics. Refer
to figure 4-1 in Section IV for location of cables and boards. Refer
to f i g u re 7-4 in Section V I I for powe r-up test codes.
Use ta ble A8-1 0 to determine which adj ustments and tests need to be
perfo rmed to com p l ete i n strument service.
S E RV I C E
8-87