HP7245A ROM problems?

I am working on an HP7245A thermal printer/plotter. I have a home-made schematic of this unit, and have read the service manual for the -B version on hpmusuem.net OK, a bit of history. It was given to me because the previous owner couldn't get it to work and suspected a PSU problem. In fact I don't think there's much wrong with the PSU (off-load, all outputs are correct), I think the logic side was trying to drive one of the motor windings hard on, and that was tripping the PSU. Currently, I've got it in bits. I've removed all the mechanical side. I have the backplane, 4 internal logic boards, HPIB interface and PSU plugged together. I've also got the the ribbon cable plugged into the I/O PCB and to the front control panels. I am trying the self-tests. I am assuming they are similar to the ones in the -B model, and that all test LEDs on (77(8)) is a pass, for example. And that the tests are in the same order and do the same things. Test 1 (processor board buffers) seems to pass Test 2 (ROM) doesn't, see below Test 4 (RAM) passes, even though the darn thing uses 2114s Tests 5,6,7, (interrupts) seem to pass too Test 10 (HPIB) passes. And I see little flashes from the 'addressed' LEDs on the back, so I think it is doing something to the HPIB card. OK, back to test 2. This would seem to be a ROM checksum test. It fails with error 54(8). It's certainly looking at the ROMs on the ROM/RAM (memory) PCB), if I pull that board it fails with a different code (which, if the codes are the same as the -B version would indicate that the lowest ROM on the ROM/RAM board had failed, which makes sense as it's not there when I pull the board). Now for the problem. if the the codes are the same, then 54(8) is 'ROM 60 LSB failed). ROM 60 (assuming that's the high digits of the octal address, which makes a lot of sense) is a ROM that's not present in the -A model (the -B has more ROM, since it can do raster dumps). The ROMs are AM9216s. These seem to 2K*8 devices, with 2 chip select lines (at least one of which has mask-programmable polarity) and need a +12V supply (although not a -ve supply as well). Does anyone have a service manual for the -A model and can look up this error code for me. And assumign it is a ROM failure, does anyone have a ROM dump, or a dead machine I can get a chip (or board) from? -tony