Hi Guys, Picked up another big load this weekend, and am just starting to go through it - Item#1 is a TRS-80 Model IV. When I first powered it up, it sucked on the Empty bottom drive for a couple of seconds, then prompted with "Cass?" and entered ROM basic. Tried a Model IV boot disk and go the same result - so I removed the drive and cleaned it (machine has been sitting a long time). Now, it powers up, selects the drive and "hangs" - does not move on to the "Cass?" prompt - I've checked all connections and socketed chips, and everything is clean and looks OK. Have reseated everthing several times. A few of observations: - If I hold RESET while I power up the machine, the drive motors still come on, but I do not get a select - the select appears to be happening under software control. - If I disconnect the disk controller board ribbon cable, the machine powers up at the "Cass?" prompt - in this case, I believe the ROM startup sees that there is no disk system and enters ROM basic, thinking that it is a diskless unit. - If I power-up/reset while holding BREAK, it also gives the "Cass?" prompt - after briefly selecting the drive - looks like BREAK very soon after power-up can interrupt the boot process, and ROM BASIC comes up normally. - I never see the drive seek - it selects, but does not seek. If I manually move the drive head out during power-off, it DOES NOT seek back to track-0 after selecting the drive when I power it on. - Twice so far in a couple of hours of working on it, I have seen the prompt "Diskette?" (no cursor) after powering on the machine (with disk controller connected and not holding BREAK). I cannot make this prompt come up reliably. It looks to me as if something in it's interaction with the disk controller is hanging the machine. Anyone here knowlegable in TRS-80's? Can anyone tell me what the Model IV is *SUPPOSED* to do on power-up, both with and without a boot disk in the drive (I have no documentation at all). Any pointers to service documentation? ROM listings? Other information on servicing a model IV - any idea how I can further diagnose this problem? Any help at all would be greatly appreciated! Regards, Dave -- dave04a (at) Dave Dunfield dunfield (dot) Firmware development services & tools: www.dunfield.com com Vintage computing equipment collector. http://www.parse.com/~ddunfield/museum/index.html