Filter
Top Products
HP Designjet T Series — Service Manual 2-39
Appendix A: How to troubleshoot SE 79:04
checks the counter from time to time to see its value and take conclusions
from it. If the counter is near 0, it means that the printer is processing
correctly, and if it grows too big, it may mean that there is a bottleneck
somewhere and maybe the JetDirect card throughput is decreased to control
its speed to the printer. However, if the access to this counter is not properly
controlled, undesirable effects may happen: in a real environment, a
JetDirect card processes thousands of information packets per second, so
this counter is updated frequently, both by the JetDirect and the printer. If at
a certain point the JetDirect and the printer try to access the counter at the
same time and the code is not prepare to handle this, it may happen that the
JetDirect cannot increase the counter because the printer is writing to it, and
what’s worse, that it does not realize this fact. If this happens a few times
each second, it may happen that the counter is decreasing faster than it’s
increasing and that at a certain point it has a negative value. And then,
what will the process that is checking this counter do? Most likely, the
process will not be prepared to react to a negative value and will launch an
exception that will trigger a 79:04 system error.
Symptoms
This type of 79:04 always occurs in heavy load conditions, so the symptoms
wi
ll always be similar to this pattern:
A printer that is being heavily used (printing a project or in a
reprographics environment) produces 79:04 errors randomly, forcing the
user to reboot.
After rebooting, the printer can be used without any issues for an
extended period of time, but if the workload is consistently high, a
random error will occur again.
The error can never be associated with a specific file. The file that was
being printed when the error occurred the last time can be printed
without issues after reboot. And a file that has been printed without issues
several times can trigger the error in the future.
This error is very dependant of the workflow the customer has. The most
common user workflows have been extensively tested both by HP and by
our beta sites, so it is highly unlikely to see random 79:04 issues in these
cases. These random issues tend to occur in very specific corner cases,
and cannot be reproduced unless the exact conditions of the workflow
are replicated. They normally happen when sending files generated by
external applications (RIPs, 3rd party drivers, etc.)
Workarounds and solutions
Random 79:04 errors are, by far, the most complex ones to diagnose and to
f
i
x. The only solutions available in these cases are:
1 Identify the root cause (either in the files or in the firmware) and fix it in the
c
ode, which requires the intervention of the GBU
2 Test any options available to modify the customer’s workflow and see if any
c
ombination of them solves the issue
In both cases, a profound understanding of the customer’s workflow is
neces
sary. In particular, the information that is needed is:
Printer front panel settings
Application that is being used; RIP or driver that is being used