HP 3562A Service Manual page 508

S E RV I C E
If at least one channel's fu nctional test passes, the fol lowi ng c i rcu its are probably function­
ing correctly:
•
G l obal Data Bus I nterface for the channel passing the test.
e
G l obal Bus DMA Control except the DMA Contro l ler (AS U307, U309) for the fai l ing
chan n e l .
•
The Add ress O utput Registers for the channel pass ing the test.
e
The D igital Fi lter subblock and associated subblo cks on the AS assembly for the channel
pass ing the test.
•
The Para l l e l I n put Contro l l i nes assoc iated with the channel passi n g the test.
e
The LO S ignal/Constant Select l i nes assoc iated with the pass ing c h a n n e l .
•
The A6 assem bly except the Com m and Reg ister and the Start/Stop Control PLA.
F I LT E R T E ST
The filter test shou ld be used, after the DFA fu nctional test is performed, to isolate problems
associated with the d igital f i l ter b locks on the A5 board . The measurement i nte rru pts are
not tested prior to perform ing this test and the i n strument w i l l hang if they do not work
correctly.
T h i s test performs the same measurement on the same data as described for the DFA
fu nctional d i agnostic test except that it uses a constant signal i n stead of the LO s ignal
for the zoom process. This means that the fu ndamental s ignal is outside the zoom window
(sub harm o n i c s are a l l that are measu red), but the measu rement resu lts are pred ictab le
to the point that i n d ividual bits m ay be checked .
The resu l ts of the fi ltering are stored i n global RAM. The system C P U then performs a
checksum on the data and compares it to known val ues. E rrors are reported for bad data
from bl ocks processed by the real and i m agi nary fi lter I Cs in c h a n n e l s one and two.
If only one of the fol lowing fai l s, start tro u b l eshooting the assoc iated l e in the CHAN 1
D igita l Fi lter or C H A N 2 Dig ita l Fi lter su bblock:
D FA Chan 1 Real Fi lter
D FA Chan 1 I mag Fi lter
D FA Chan 2 Real Fi lter
D FA Chan 2 I mag Fi l ter
I f both real and im agi nary fa i l fo r a given channel, troub les hoot the contro l l e r c h i p or
the fi lter bus i nterface c h i p associated with it. The three I Cs i n the d igital fi lter bl ock
of each channel are mou nted i n sockets and may be switched to verify operation. However,
f u rther use of the d i agnotic tests is recommended before you beg i n sw itc h i n g I Cs.
I f both real or both i m ag i n a ry fi lter tests fai l , tro u b l eshoot the LO s ignal selection block
on the AS board .
8-58
MO D E L 3S62A