Emax SCSI, The Plus Model

Overview One of the last upgrades to the Emax was to provide an external SCSI connector so that external SCSI hard and removable drives could be connected to the Emax. This upgrade followed on from the internal SCSI capability that was added for an internal hard disk, as contained within the HD models.Production keyboard and rack models came out the factory with this capability in 1989, and were denoted as Plus models. The upgrade could also be retrofitted to later (but NOT earlier) Emax keyboard and rack models.Why do I need external SCSI ? You can save and load samples to a ZIP100 drive, and you can get expand you library of samples by buying ZIP100 cartridges full of 36 new OMI sample banks from us!

Can I upgrade my Emax with external SCSI? First you need to know which digital board you have, the revision and part numbers are printed on the board in white.

  • Revision 1 Part Number 320 – IMPOSSIBLE TO UPGRADE
  • Revison 2 Part Number 320 – POSSIBLE TO UPGRADE
  • Revison 3 Part Number – POSSIBLE TO UPGRADE

Next you need to check whether you already have SCSI installed. Look on the digital board for all of these:

  • A 5380 SCSI chip at IC6
  • The 28-pin Plus OS boot ROM labelled IP355 at IC13
  • The HD or Plus TIM PAL at IC49 (IP356 or IP379) 

If you have these parts fitted its a simple matter to extend the SCSI cabling to provide an external connector, and a simple OS modification to provide selection of the SCSI ID. Unfortunately the OS was NOT modified to format or read/write a larger disk space than 20 MB. Even a maximum of 100 banks at 512kb would have been nice, at 50 MB !

Upgrade Kit If you don’t have these chips fitted, you can buy an upgrade kit with these components from us:

  • One 5380 SCSI chip
  • One Emax Plus Boot ROM
  • One Emax Plus TIM PAL
  • An external SCSI adapter connector
  • The OS Plus software on diskette
  • A hard copy of the E-mu Systems install instructions

Read the instructions opposite first as you’ll need a service tech to install the upgrade if you have a Rev 2 board. Rev 1 digital boards can not be upgraded as there is no space on the board for the SCSI controller.

OS Plus Feature The Plus OS has only one additional feature – the ability to select a SCSI id. Press and hold the Transpose key, the display will show:


Press the numeric key which matches the SCSI id of the drive you want to access, and if this drives is active on the SCSI bus it will be used as the Emax active drive.

External ZIP 100 Drive Whilst the Emax predates the Iomega Zip 100 drive by nearly 10 years, it still works a treat! Connect the standard Zip 100 drive to the Emax Plus using a 25 – 25 pin SCSI cable. Select the drive ID (as above) and format and read/write as usual.

intern zipInternal ZIP 100 Drive An even cooler upgrade is to fit an internal SCSI Zip 100 to replace the floppy drive in a HD or Plus model. This means replacing or supplementing the internal hard disk. You will need to rig up both the ZIP drive and the floppy, so you can copy all your sample library onto ZIP disks first. The PSU may not be able to cope with both a hard drive and ZIP drive, as the ZIP requires 0.3 A more than the floppy drive. The hard disk is noisy anway so best use just the internal ZIP, and set the ZIP SCSI ID to 0, then the Emax will boot from ZIP.

Technical The SCSI upgrade is based round the NCR5380 SCSI-1 controller chip which was developed by NCR in 1984. It gained immediate use in the Apple Mac, thanks to it being the first low cost SCSI controller chip. It runs the SCSI bus at 1.5 MB per second.

More For more information how to upgrade SCSI at Emax check also: https://djtbs1.wordpress.com


Emax Plus SCSI Retro Instructions

Emax SCSI Interface Instructions

Stage 1

The Emax HD can be fitted with external SCSI by extending the internal SCSI cabling to an external SCSI adapter mounted on the rear of the Emax. You will need the Plus OS diskette (email us).

The Emax must have:
A 5380 SCSI chip
28-pin SCSI boot ROM
The right PAL chip.
See this picture for details.

internal SCSI

Stage 2

If you are keeping the internal hard drive, buy a 3 device 50-pin internal SCSI cable. You can keep your existing SCSI cable if you are eliminating your internal hard drive.

flat cabel

Stage 3

Get a SCSI adapter that has an internal IDC50 male connector and an external DB25 female connector, mounted on a PC bulkhead backplate bracket.

When you get the adapter cut the mounting plate at both ends to ensure it is a flush fit on the Emax casing. Drill two mounting holes in the plate. Locate suitable mouniting bolts and nuts.

ext scsi

Stage 4

A hole needs carefully cutting in the rear Emax casing for the adapter to fit. The Emax casing needs to be opened up and ALL electronics and internal parts MUST be masked off to ensure NO casing swarf gets to them. We used a sheet and lots of masking tape. The casing material of both the rack and keyboard is conductive. Use the adapter as a template. We the adapters opposite the hard drive on keyboard models. On rack models you may want to dettach all the connectors from the casing so you can work on it separately. Check your internal SCSI cable can reach the adapter before drilling!

hole in emax scsi

Stage 5

Fit the adapter to the casing and connect up the internal SCSI cable. Include the internal hard drive if you decide to keep it.

fitting scsi

Stage 6

Here is another picture of the internals. The internal hard drive has been removed.

fitting scsi 2

Stage 7

Remove all casing swarf. Unmask the internals. Close the casing. Attach an external SCSI device such as a ZIP100 drive (terminated), with a 25pin – 25 pin external SCSI cable. Power up with the Emax Plus OS diskette. Format a new ZIP cartridge, and save all your samples onto it !


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