Macintosh LC II not being able to see two hard drives at the same time

[gkmaia]

I got an LCII with a hard drive inside.

 

As I wanted a second hard drive I decided to make an adaptor to connect my other SCSI drive to it's rear SCSI port.

 

If I start with the external HD connected it boots from the external Hd and the internal is not visible.

 

If I start with the internal HD and later connect the external HD the external does not mount.

 

Anything I should do such as setting the external as slave? Or come pinout on my adapter that I am missing?

[tunk]

Maybe they have the same SCSI ID?
https://en.wikipedia.org/wiki/SCSI#Device_identification

[gkmaia]

that makes sense, thanks!

they both mount at bus 0. I will see if I find a jumper to change their scsi id.