You are correct, Tony, board swapping tricked me (this time)! I think I can forget the RK07 drive for now, and concentrate on the RK611 controller. First, I checked the flat cable from the controller M7904 (drive interface) module to the home-made bulkhead. That flat cable is 100% OK. The round cable from the bulkhead to the drive is NOS, and the label is 70-12292-25, so I'm sure it is the RK06/RK07 drive cable, not the RL0x cable. Before pulling out all kind of equipment, I started with what a DEC engineer probably also would do: run the diagnostics! So, I loaded XXDP and ran ZR6A??.??? which is the test "RK611 diskless controller diagnostic #1". Here is the output. .R ZR6A??.??? ZR6AD0.BIN RK611 DISKLESS DIAGNOSTIC: PART 1 CZR6AD0 @ ATTEMPTING TO CLEAR CS1 WITH A SUB CLEAR BUS ADD INCORRECT TEST ERROR NUM PC 000041 033024 PREV EXPECT ACTUAL VALUE VALVE VALVE 013776 000200 100200 So, there is already a problem with the RK611 controller reported after the diagnostic runs some 5 seconds! A few months ago I scanned a pile of XXDP doc, but the ZR6A et al. was not amongst them :-( I am not sure I have a spare RK611 controller board set (going to the attick after this e-mail), but can somebody tell me which board is likely to be suspected? thanks, - Henk. ________________________________ Van: cctalk-bounces at classiccmp.org namens Tony Duell Verzonden: zo 22-01-2006 19:51 Aan: cctalk at classiccmp.org Onderwerp: Re: RK07 questions Do you know that the controller and cabling are OK? Or could the fault not be in the drive? -tony This message and attachment(s) are intended solely for the use of the addressee and may contain information that is privileged, confidential or otherwise exempt from disclosure under applicable law. If you are not the intended recipient or agent thereof responsible for delivering this message to the intended recipient, you are hereby notified that any dissemination, distribution, or copying of this communication is strictly prohibited. If you have received this communication in error, please notify the sender immediately by telephone and with a "reply" message. Thank you for your cooperation.