Emax : Diagnostics (Magic Mode)

Diagnostics and Trims The Emax is a powerful and complex instrument. To service the Emax you need to be familiar with 7400 TTL digital logic, floppy disk drives, ADC's and DAC's, op-amps, as well as microprocessor troubleshooting. Luckily E-mu Systems have provided a diagnostic mode within the Operating System to help trouble- shooting, when something goes wrong. Download the manual for detailed information on diagnosing a problem and performing the factory test of functionality.

Emax Diagnostics  (210 KB / 17 pages)

Diagnostics Vary by OS Version The Emax OS was expanded from 1985 - 88 to provide support for new hardware and software features, the diagnostics also expanded over time too. So the access rountines and functionality depends on OS version. A "magic code" was necessary for later models.

Base Emax Diagnostics If you have a basic Emax then the diagnostics can be accessed by the following procedure:

Active module 8 (Special), then activate the sub module 2 higher than the last visible choice (this is usually 8). The LCD will show
             EMAX DIAGNOSTICS
          ARE YOU SURE Y/N

Go ahead and enter Y. The display will now show:
             EMAXDIAGNOSTICS
          ( 1 - 7 }  Slider

Emax SE Diagnostics  The Emax SE procedure is as follows:

Active module 9 (Special), then activate the sub module 1 higher than the last visible choice (This is usually 9). The LCD will show
             EMAX DIAGNOSTICS
          ENTER CODE

Go ahead and enter 3629. The display will now show:
             EMAXDIAGNOSTICS
          ( 1 - 9 )  Slider

Emax HD SE Diagnostics  However later serial number Emax's have the following procedure - complete with Magic Code. 

Active module 9 (Special), then activate the sub module 1 higher than the last visible choice (This is usually 9). The LCD will show:
            EMAX DIAGNOSTICS
         ENTER CODE 

Go ahead and enter 3629. The display will now show:
            EMAXDIAGNOSTICS
         ( 1 - 9 )  Slider.

Diagnostic Sub modules There are up to 9 sub modules that can be selected and exited in the normal way:

  1. Bank RAM check
  2. ERAM check - checks the sample memory (useful)
  3. RS422 Test
  4. Write Verify Test of the Floppy Drive (useful)
  5. Verify Floppy Test (useful)
  6. Panel Tests (useful)
  7. Filter Trims (useful)
  8. Volume Trims (Emax SE onwards)
  9. HD Diagnostics (HD models only)

HD Diagnostic Sub module  There are 7 sub modules that can be selected and exited in the normal way:

  1. SCSI/Echip
  2. Read Only
  3. Read/write
  4. Burnin HD
  5. Show Ressults
  6. Show HD All
  7. Media Defects

MUST These functional tests rely on a special disk of sounds and sequences called the Max Universal Sound Test (MUST). If you have this please let us know.

Common Emax Problems The first component of the Emax to check is the power supply. Common problems are caused by connectors, sockets and broken solder joints. Check you have the latest copy of the software (3.2 for base models, 1.1 for SE/SE HD), as early versions have quite a few bugs.

The most frequent problems are due to the power supply and the disk drive, neither of which are field repairable. Component failures centre around the E-chip, and the SSM chips (especially the SSM2300).

The floppy disk drive usually fails after 10 years use, and the LCD also fades over time. The floppy drive can be replaced with a modern drive provided it can be set to an id of 0 with jumpers. This rules out most modern drives except the TEAC 235HF-A529. This is available in black, but is half height and therefore leaves a gap in the front panel. E-mu supply the Sony MPF920 (black, half height) but at an excessive price.

Replacement LCD's can be obtained from E-mu.

Common Early Problems The Emax had a few early teething problems. Most Emax's should have seen these problems sorted out long ago . . .

Voice Channel Static This is caused by the ribbon cable which connects the digital and analog circuit boards picking up RFI, because it's too long. The solution is to tape/tie clip the cable loop closely together, or replace it with a new shorter one.

Disks Fail to Load  If the floppy disk drive fails to load disks, it could be out of alignment - in which case it will need replacing. E-mu switched to using a Mitsubishi drive (which needst OS 3.1 or higher), as these drives are more reliable than the original NEC's. Nowadays E-mu supply the Sony MPF920 as a replacement or you can use a TEAC 325HF - A529.

Another cause of disks failing to load is due to firmware. If you have the early Boot ROM Version A (marked Rev A), replace it with the newer Boot ROM Version B or C.

E chip

Daughter of E The E-chip technology broke new ground as a custom DSP chip. However because of variances in its manufacturing, some chips need to run off a higher voltage to work.

Rather than waste these out of tolerance E-chips, E-mu Systems fitted a daughter board onto the mainboard, with a higher voltage supply and modifications to clamp the output voltages back into range. This increased the yield of E-chips.

Any Emax that needs this fix should have already received it, as an E-chip out of spec causes major problems that the initial user will have reported. The symptoms of this problem are digital distortion. Even late model Emax's used the daughter board, as the production of E-chips still had variability in quality.