Installed Windows 10 via BCA, OSX no longer boots, prohibited sign displayed

Hi,

I recently took the plunge and installed Windows 10 via BootCamp Assistant on my late 2014 Mac Mini (core i7 with SSD) from USB stick.

Installation of Windows went mostly fine and Win 10 RTM is up and running so far so good - haven't installed the Apple Bootcamp drivers yet, waiting for the official Windows 10 supported ones, but for now default drivers seem ok.

One huge problem however, is that after installing Win 10, I can no longer boot back into the Mac OS X partition. When booting and holding down the option key and selecting the Mac partition, a grey screen appears with the prohibited sign.

I suspect the Windows installation maybe played around with the disk partitions a bit and now something is out of sync. Looking at the partition table it could be the new Windows Recovery partition that it created? Need some advice on this if anybody on this board can help...

Luckily I have a spare external USB hard drive with ElCapitan DP5 on it that I created before installing windows so I can boot into this and run Mac OS to help diagnose the issue on this Mac. Windows boots normally of course.

I've copied down the output of the following commands if it helps someone to diagnose and advise.

Thanks in advance!

Rob

Commands used:

1) diskutil list

2) diskutil cs list

3) sudo gpt -vv -r show /dev/disk0

4) sudo fdisk /dev/disk0

Output from Mac (using 10.11.DP5 booted from external USB disk):

1)

$ diskutil list

/dev/disk0 (internal, physical):

#: TYPE NAME SIZE IDENTIFIER

0: GUID_partition_scheme *251.0 GB disk0

1: EFI EFI 209.7 MB disk0s1

2: Apple_CoreStorage Macintosh HD 190.4 GB disk0s2

3: Apple_Boot Boot OS X 650.0 MB disk0s3

4: Microsoft Basic Data 59.3 GB disk0s4

5: Windows Recovery 471.9 MB disk0s5

/dev/disk1 (internal, virtual):

#: TYPE NAME SIZE IDENTIFIER

0: Apple_HFS Macintosh HD +190.0 GB disk1

Logical Volume on disk0s2

CD8D5A0E-8865-46D5-A653-D8CF745008F6

Unencrypted

/dev/disk2 (external, physical):

#: TYPE NAME SIZE IDENTIFIER

0: GUID_partition_scheme *500.1 GB disk2

1: EFI EFI 209.7 MB disk2s1

2: Apple_HFS ElCapitan 499.2 GB disk2s2

3: Apple_Boot Recovery HD 650.0 MB disk2s3

2)

$ diskutil cs list

CoreStorage logical volume groups (1 found)

|

+-- Logical Volume Group 7A6E407A-C6D2-4A76-AEBC-FB646349F508

=========================================================

Name: Macintosh HD

Status: Online

Size: 190361247744 B (190.4 GB)

Free Space: 8921088 B (8.9 MB)

|

+-< Physical Volume E9B22150-1E3A-43AB-963C-3985B499430E

| ----------------------------------------------------

| Index: 0

| Disk: disk0s2

| Status: Online

| Size: 190361247744 B (190.4 GB)

|

+-> Logical Volume Family DE842B21-5F41-4EF7-B671-F7FFF6E199FB

----------------------------------------------------------

Encryption Type: None

|

+-> Logical Volume CD8D5A0E-8865-46D5-A653-D8CF745008F6

---------------------------------------------------

Disk: disk1

Status: Online

Size (Total): 190000005120 B (190.0 GB)

Revertible: Yes (no decryption required)

LV Name: Macintosh HD

Volume Name: Macintosh HD

Content Hint: Apple_HFS

3)

$ sudo gpt -vv -r show /dev/disk0

gpt show: /dev/disk0: mediasize=251000193024; sectorsize=512; blocks=490234752

gpt show: /dev/disk0: PMBR at sector 0

gpt show: /dev/disk0: Pri GPT at sector 1

gpt show: /dev/disk0: Sec GPT at sector 490234751

start size index contents

0 1 PMBR

1 1 Pri GPT header

2 32 Pri GPT table

34 6

40 409600 1 GPT part - C12A7328-F81F-11D2-BA4B-00A0C93EC93B

409640 371799312 2 GPT part - 53746F72-6167-11AA-AA11-00306543ECAC

372208952 1269536 3 GPT part - 426F6F74-0000-11AA-AA11-00306543ECAC

373478488 936

373479424 115832832 4 GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7

489312256 921600 5 GPT part - DE94BBA4-06D1-4D40-A16A-BFD50179D6AC

490233856 863

490234719 32 Sec GPT table

490234751 1 Sec GPT header

4)

$ sudo fdisk /dev/disk0

Disk: /dev/disk0 geometry: 30515/255/63 [490234752 sectors]

Signature: 0xAA55

Starting Ending

#: id cyl hd sec - cyl hd sec [ start - size]

------------------------------------------------------------------------

1: EE 1023 254 63 - 1023 254 63 [ 1 - 490234751] <Unknown ID>

2: 00 0 0 0 - 0 0 0 [ 0 - 0] unused

3: 00 0 0 0 - 0 0 0 [ 0 - 0] unused

4: 00 0 0 0 - 0 0 0 [ 0 - 0] unused