Looking at the ELOG, there seem to be many cases where there is an error in a PPC window, and one of the remedies that is tried is to cycle the power in one or more of the FAstbus crates (often the master crate).
Our experience has been that this very rarely solves the problem so I would like to discourage people from doing it, especially since there can be negative side effects from cycling the power, such as screwing up TD/CCD pedestals or damaging a SSP hybrid or blowing a fuse on an SSP.
If the PPC window shows a dump of what looks like assembler instructions, then cycling the power will almost certainly not work. If the PPC window shows an error at SSPinit that looks like a bit is missing when the memory readback value is compared to the written value, again cycling power is very unlikely to succeed.
The first thing to try if there is an SSP error is to repeat what you were trying to do and see if the problem is repeatable. The other thing is to check the SSP hybrid voltage levels by going to http://bnlku33.phy.bnl.gov:8081/SC/Cable Segment?exp=E949
The numbers should all read around -110 mV except for the SR line (which is usually some large value) and the AL0-5 lines (which are often at positive 110 mV). If one of the values is around 0, that probably means that a hybrid on one of the SSP's in the cable segment has gone bad. To figure out which SSP on the chain has the bad hybrid, follow the procedure described at: http://www.phy.bnl.gov/e787/newfixssp/newfixssp.html
or give me a call.
Thanks.
- George