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Emax : Repairs
Overview The Emax is a reasonably reliable product but you may encounter problems now it is 15 years old. The main problem areas are the PSU, the keyboard and the LCD. Some parts are simply impossible to locate, such as housings etc.
Warning Please only attempt a repair yourself if you are competent at servicing electronics, use a service centre if in doubt. The Emax is easily damaged or melted by amateur attempts at repair.
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Typical LCD
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LCD Overview The Emax uses a 16x2 character LCD with an EL backlight. When new the display is bright blue with grey/black characters. The LCD
does fade dramatically over time, and the backlight can fail or the inverter that drives it can fail too. E-mu Systems used a variety of LCD manufacturers.
LCD Age After around 2000 hours use the LCD will need
replacement, and its a good idea to replace the LCD whilst parts are still available. E-mu Systems no longer have spare LCD's.
LCD Angle The viewing angle of the LCD needs setting up so you
can see the display from above the keyboard or rack. The LCD is designed so that the angle is controlled by a voltage on pin 3. Viewing angle changes also cause changes in the contrast
between characters and the background colour of the LCD. E-mu Systems provided preset viewing angles, and it wasn't until the Emax II was designed that viewing angle was under software control.
On the Emax the viewing angle is preset. On early keyboards this was done by a couple of 1% resistors, on later keyboards an internal preset potentiometer near the CN6 connector varies the
angle. On all rack units a small electronic circuit provides a negative voltage for the LCD viewing angle. A preset potentiometer varies the angle so that the LCD to be viewed from below.
LCD Part Number There are a variety of LCD's you can use as replacements, some have the same blue backlight, others have a green or yellow
backlight colour - as per Emax II's. You can use LCD's with EL backlights (as per the original) or experiment with LED backlights which last longer but need a different power supply
for the LED's (typically 4.2V 120mA rather than 140VAC 400 Hz ). The new LCD must be the same size of 85 x 36 mm and use the same connection layout of a double row of 14 data connections and 2 separate backlight power connections.
A typical LCD is the PowerTip PC1602-H available from RS Components. This is a 16x2 LCD with purple/white EL backlight.
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Digital Board
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LCD Inverter The LCD backlight (the blue colour) is driven by a small inverter that generates 100VAC at 400 Hz from a 5V supply. The inverter
on the Emax is a NEC (NEL-D32-46), and its a small black plastic box that sits on the digital board - see the picture. The inverter can fail, which means no blue backlight, in which case it
needs replacing. If you replace the LCD with a different model you will need to ensure the inverter is a match for the LCD.
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Front Panel PCB
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LCD Replacement The LCD can be replaced very easily. You will have to remove the front panel PCB, by first removing the digital board which sits
on top of it and the keyboard. Then you can unplug the LCD from two sets of sockets on the front panel PCB (one 14 pin the other 2 pin). The new LCD will need to have extended pin headers
soldered onto it, one 14-pin the other two single pins. 2-pin other 2-pin. It's not worth trying to desolder the headers on the old LCD. The picture shows a LCD module with headers unplugged from the front panel PCB. |
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 3.5" Floppy Drive
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 The Emax floppy drive was orginally a NEC, but later models have a Mitsubishi Full Height 3.5" MF353B - 12 UJ or MF353BA - 12U.
Buying
Try your loacl TEAC dealer
Or contact Route66 Studios
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TEAC Floppy Disk Drive
Jumper Settings
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Slider Knobs |
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The Emax has two slider buttons, we don't have a known replacement.
The Emax
front panel buttons are a rubber/plastic moulding which is impossible to replace new.
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Keyboard |
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The Emax keyboard is prone to cracked and damaged keys, although the mechanism is
robust and seldom fails. Unfortunately the keyboard can not be easily repaired and it must be replaced as a whole. Replacements are not available new from E-mu Systems, and are not available new. Repairing individual keys is difficult too.
Try www.eprelectronics.com
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Hard Disk |
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 The Emax HD uses a 20 MB SCSI drive, the MiniScribe 8425S or 8425SA. It has a service life of around 20,000 hours, so most are dead or likely to die soon. It
can easily be replaced either new or s/h from an Apple Mac computer - where it was a standard fit in the mid 1980's.
The Emax can also be used with the Rodime RO652 20 MB drive, it is slightly slower on sample loads and has a much
shorter life span. They are very rare these days.
We recommend upgrading your Emax HD with external SCSI and using an external ZIP100 drive. This is faster and quiter, plus you now have infinite storage ! You can then
ditch your noisy internal hard disk ! Upgrade details are here... more »
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Miniscribe 8425S
Jumper Settings
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Power Supply |
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 The power supply is getting old by now and failure is not uncommon. One of the rails may go out of specification. Replacement
PSU's are not available, so the best option is a service centre repair.
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