HP 3562A, Service Manual

Page: 508 / 570

SERV I C E
MOD E L 3S62A
8-58
If at least one channel's fu nctional test passes, the following circu its are probably function­
ing correctly:
•
G lobal Data Bus I nterface for the channel passing the test.
e
G l obal Bus DMA Control except the DMA Control ler (AS U307, U309) for the fail ing
channel.
•
The Add ress Output Registers for the channel passing the test.
e
The Digital Fi lter subblock and associated subblocks on the AS assembly for the channel
pass ing the test.
•
The Parallel I n put Control l ines associated with the channel passing the test.
e
The LO Signal/Constant Select l ines associated with the passing channel.
•
The A6 assem bly except the Com mand Register and the Start/Stop Control PLA.
F I LTER TEST
The filter test shou ld be used, after the DFA functional test is performed, to isolate problems
associated with the d igital filter b locks on the A5 board. The measurement interru pts are
not tested prior to perform ing this test and the instrument w i l l hang if they do not work
correctly.
This test performs the same measurement on the same data as described for the DFA
fu nctional diagnostic test except that it uses a constant signal instead of the LO signal
for the zoom process. This means that the fu ndamental signal is outside the zoom window
(subharmonics are a l l that are measu red), but the measu rement resu lts are pred ictab le
to the point that individual bits m ay be checked .
The results of the fi ltering are stored in global RAM. The system CPU then performs a
checksum on the data and compares it to known val ues. E rrors are reported for bad data
from blocks processed by the real and imaginary fi lter ICs in channels one and two.
If only one of the fol lowing fai l s, start troubleshooting the associated l e in the CHAN 1
Digita l Fi lter or CHAN 2 Digital 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 Filter
If both real and imagi nary fail for a given channel, troub leshoot the control ler chip or
the fi lter bus interface chip associated with it. The three ICs in the d igital fi lter block
of each channel are mounted in sockets and may be switched to verify operation. However,
further use of the diagnotic tests is recommended before you begin switching ICs.
If both real or both imaginary fi lter tests fail, troubleshoot the LO s ignal selection block
on the AS board .