MicroVax II diagnostic tape?

Well, I managed to unjam the TK50 drive and get the cartridge out - it took some fiddleing, manually rewinding the tape with the screw hole in the bottom a bit, powering up, it would seek back and forth, then start to rewind, go a ways, then stop. Lather, rinse, repeat about three times, and then it got stuck right before the unload cycle. Manually rewound the last few inches and unlatched/removed the cartridge. The leader looks OK, but the cartridge is a little "crinkly" sounding - I think it must have jammed up in there somehow. Anyway, I don't think this tape is going to be useable. The closest thing I had lying around is a DLTTape IIIxt cartridge - which, by creative people who must have thought of this before, doesn't fit. Little tabs on the left of the tape prevent it from being inserted all the way. So, I'll sort through tape drives and see if I can find the SCSI TK50 I think that I have. Either way, I have three DEC interface TK50's - so I should have one that I can make work. I'll try messing with the Emulex controller system first, especially if I can make it load internal diagnostics. I have several ESDI drives kicking around I can put into service. The one that's in there certainally sounds "crashed" but I'll try and see if it can work at all. I don't see anything dragging on the motor externally. It's a CDC Wren something-or-other drive. As far as the RD53 on the stock DEC Vax, I dismantled the drive and unjammed the heads. It now spins up and performs a head load, and stays spinning. The Vax still won't boot though, although it doesn't give me any errors on the console. It gets to "2...", and the "READY" lamp on the front of the Vax blinks a bit, pauses, blinks a bit more, then stays on. I'd like to try reformatting it and see if it works. I know that the MFM based drives are old, and probably unreliable, but I have several, and I'm not at all against using them if I can get something to run. -Ian