HP 9845 C with 280 option startup failure

[Tequi Lizer]

I recently acquired a HP 9845C option 280 (was looking for it for a 
really long time).

The machine is in an overall good condition, however it hangs during 
memory test ("MEMORY TEST IN PROGRESS"), even after cleaning all board 
connectors, resocketing all ROMs & repeated control-stop's. Before 
entering nirvana the printer outputs a couple of memory addresses. 
Although lots of defects may be responsible, I assume there is a 
combination of both a bad RAM chip and a ROM failure, since a RAM defect 
alone should (?) not crash the system during the test.

The printout looks like this:

000000 100112 052525
000000 110112 052525
000000 120112 052525
000000 130112 052525

I guess the first number is the block ID, the next is the memory address 
within the block, and the last number is the test pattern, each in octal 
representation.

Does anyone have an idea

- how to really interpret the memory test printouts and

- how to check the ROMs for bad data?

Maybe there is anyone out there who did the job to read out the contents 
of his 9845 ROMs (they are all in sockets) for a direct comparison. 
There is a 98407A memory option installed, and, of course, a bit slice 
LPU. So the ROMs work out as:

PPU assembly:

    CE1 LB:    1818-1591B
    CE1 UB:    1818-1592B

    CE2 LB:    1818-0846D
    CE2 UB:    1818-0841D

    CE3 LB:    1818-0837D
    CE3 UB:    1818-0833D

    CE4 LB:    1818-1898A
    CE4 UB:    1818-1899A

LPU assembly:

    CE1 LB:    1818-1506A
    CE1 UB:    1818-1502A

    CE2 LB:    1818-1507A
    CE2 UB:    1818-1503A

    CE3 LB:    1818-1508A
    CE3 UB:    1818-1504D

    CE4 LB:    1818-1509A
    CE4 UB:    1818-1505A

Most of them schould be the same as in an 9845B model 200 system.

Thanks for your help
Ansgar