HP 3562A Service Manual page 540

S E RV I C E
B. A8/A1 7 Circuit Block Tests
T h i s section i n c l u des th ree groups of tests which wi l l f u rther isolate f a i l u res on the A8
and A 1 7 boards. Some of the tests i nvolve signatu re analysis. The A8 board m u st be on
an extender card for tests 1 and 3 .
Test 1 , D is p l ay Co ntro l, tests the D isp l ay D i rect Memo ry Access portion of the A8 board.
I t verifies correct operation of the add ress and word cou nters, d is p l ay refresh cou nter,
and the d i s p l ay contro l ler.
Test 2, D i s p l ay I nterface, covers p roblems on the A1 7 board.
Test 3, G loba l RAM, tests ope ration of the arbiter, refresh address counter, and mem ory
address sections of A8.
1 . D i s p l ay Co ntro l
a. D is p l ay Refresh Timer
• Turn on power.
• Using an osci l l oscope, check the fol lowing clock signals in the Display Refresh
T i m e r c i rc u its b l o c k :
b . D i s p l ay Contro l ler
Check T P 5 , TP6, a n d T P7 f o r the waveforms shown i n tab le A8-9 -1 .
c . D i s p l ay DMA Address Counters and Drivers
The fol lowing signatu re analys is test ve rifies correct operation of the D is p l ay
DMA c i rc u itry .
• Con nect the si gnature ana lyzer accord ing to tab le A8-2 .
Table A8-2
8-90
Signal
F requency
ClK 8 M H z
TP3 61 H z
61 H z
SYNC
Display Control/er Signature Analyzer Setup
Signal Polarity
G round
Clock Negative edge
Stop Negative edge
Start Negative edge
Connection
AB ) 1 -1
AB J 1 -3
AB J 1 -4
AB J 1 -5
MOD E L 3562A