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--- x68000:black_screen_on_xvi_hd_and_potentially_other_hd_computers [2018/12/28 11:45] – created leonk
+++ x68000:black_screen_on_xvi_hd_and_potentially_other_hd_computers [2018/12/28 17:04] – [Problem and solution] leonk
@@ Line 1: / Line 1: @@
-====== Background ======
+===== Background =====
-The X68000 XVI HD and other HD computers all suffer from the same 2 main problem:
+All X68000 computers suffer from the same 2 main problems:
   * Bad power supply (due to blown capacitors and other failures)
   * Dead SRAM save battery
-Assuming you did a full capacitor kit on the computer, replaced or fixed the power supply and installed a new save battery to store SRAM settings, you might still get a black screen on bootup.  A good working X68000 will typically show the following screen:
+Assuming you did a full capacitor kit on the computer, replaced or fixed the power supply and installed a new save battery to store SRAM settings, a good working X68000 will typically show you the following screen:
+{{:x68000:insert_disk.png?nolink&400|}}
+But on an XVI HD and potentially other HD computers, you might get a black screen.  This tutorial will show you how to fix this problem.
+===== Verify you have a good computer =====
+Boot up the computer while holding the CLR button.  If you get a screen asking you to initialize the SRAM, press Y.  You can also verify you have a good working computer by pressing the INTERRUPT button on the top.  If Japanese text pops up, then the video subsystem and system ROM is working correctly.
+===== Problem and solution =====
+It seems the HD version of the X68000 computers requires a hard drive to boot.  The SCSI hard drive chain beings at the bottom I/O board, it connects to the external I/O adapter and lastly ends at the internal drive. The end of a SCSI chain must always have terminating resistors.  Internal hard drives, or external hard drives/CD-ROM drives will have these at the end of the chain.
+If you don't have any SCSI devices connected, the system ROM hangs waiting for the SCSI device.
+To solve this problem, simply connect a SCSI device to the external output (like the SCSI2SD solution) or an internal SCSI hard drive with a terminator. Or, you can add an external SCSI terminator to the SCSI port, or add the missing terminator resistors internally (the internal resistors might prevent you from using an external SCSI2SD solution)
+You can also confirm you have this problem by looking at the external I/O adapter.  As you can see in the picture, the terminating resistors are missing (empty black sockets under the ribbon cable)
+{{:x68000:scsi_connector.png?nolink&400|}}
+Here's how an externally terminated connector will look like, when it's terminated internal to the X68000.
+{{:x68000:scsi_terminated.png?nolink&400|}}
+Installing an external terminator on the SCSI-1 connector (Centronics 50 pin male external passive terminator) should also close the SCSI bus and make the floppy drives bootable, preventing the boot ROM from hanging the system.
+{{:x68000:scsi_ext_terminator.png?nolink&400|}}