NOTE: Use at your own risk. Author is not liable or responsible for mishaps.
The Alesis Quadraverb is one of my favorite guitar
effects units. These vintage units regularly show up on
eBay, often listed in "AS IS" condition with the LCD display
being dead or erratic. Nowadays, replacement LCDs are hard
to come by, probably cost more than the Quadraverb is worth.
Here is how I fixed my broken display.
After reading various discussions on lists regarding
replacing these LCD displays, it was evident that almost
any 2x16 LCD module that followed the HD44780 LCD controller protocol
would work. However, most OEM LCD modules has a 14-pin (or 16-pin) inline
connector instead of the 14 pin header found on the stock module.
This is an eazy fix as its just a matter of reworking the Quadraverb
connection to the LCD.
I did a search for a suitable LCD module, something that looked like a
good physical fit, a greenish/yellow backlight, and inexpensive.
The KEST 1602A-01 LCD display available from All Electronics
(www.allelectronics.com, CAT# LCD-120) looked like a good prospect. I believe these are all gone by now, but there are several available on eBay (search for "16x2 LCD"). Just check that it is HD44780 compatible and the size of the module is something like "80 x 36 x 13.5mm". You'll have choices for color preference. Also make sure about how to power the backlight. Ideally you'll want something that will work off 5V. Some backlights will need an external resistor to regulate the backlight current to manufacturer's spec. If you are not careful about this, the backlight might have a very short life!
Note the 1602A is slightly smaller than the stock module
(see module on the left), however, loosening the LCD fixing screws on the Quadraverb panel just slightly, allows the 1602A module to fit snugly in position. A dab of glue on the screws holds the module in place permanently (see picture).
Reworking the electrical connection is fairly straight forward.
I made up a transition connection using a short piece of 14-way ribbon
cable and attached a 14-pin female IDC header at one end (shown here).
Strip and tin the other end of the transitional 14-way ribbon cable wire ends
as these need to be soldered to the 1602A module.
Solder the 14-way ribbon as follows (check your work wiring with an ohm meter).
IDC-end ----- LCD-end
--------------------------
2 .................... 1 (GND)...[NOTE POLARITY SWITCH!!]
1 .................... 2 (+5V)....[NOTE POLARITY SWITCH!!]
3 .................... 3 leave unconnected (see backlight wiring below)
4 .................... 4 (R/S)
5 .................... 5 (R/W)
6 .................... 6 (E)
7 .................... 7 (D0)
8 .................... 8 (D1)
9 .................... 9 (D2)
10 .................10 (D3)
11 .................11 (D4)
12 .................12 (D5)
13 .................13 (D6)
14 .................14 (D7)
-- .................15 backlight, connect to +5V (pin 2 above)
-- .................16 Backlight, connect to GND (pin 1 above)
Finish off the backlight wiring at the 1602A module (you are sure about power requirements for the backlight. Yes??): Wire +5V (pin 2, LCD)
to pin 15 (backlight), and GND (pin 1, LCD) to pin 16 (backlight). Note the 1602A module has a built-in series resistor to accomodate a 5V supply. No external current-limiting resistor is needed for this particular LCD module.
One final bit of wiring to set the contrast of the 1602A:
Connect the ends of a 20K trimpot to LCD pins 1 and 2 respectively, the
wiper goes to LCD pin 3. I used a 3/8" square pot and soldered the legs
directly to the LCD. Besure that the trimpot does not interfere with the
covers or other nearby components or wiring. Alternatively, connect a 1N4148 diode between pins 1 and 3 (the diode's ring/stripe end goes to pin 1).
Install the 1602A replacement LCD module and put a dab of glue on the screw heads.
Now there are two female 14-pin headers, one from the Quadraverb side,
the other from the replacement LCD. Snap off a piece of 0.1"-pitch,
double-header stock (14-pins worth) and use it to interconnect the two
14-pin IDC headers.
NOTE: The Quadraverb's ribbon cable is a bit unconventional: the red stripe side and the alignment notch on the IDC header are opposite to usual convention. The Quadraverb cable has pin 1 (5V) and 2 (GND) on the opposite side to the red stripe. Be sure to align the LCD header correctly, like so .
Power up the Quadraverb. If you installed a contrast trimpot, adjust for best contrast. Otherwise, for the diode modification, contrast should be good to go. If all went well, this is what my QV+ looks like. This is my QV GT fitted with a white-on-blue LCD.
A final note: Judging from the scratches on the covers of my unit, it has
seen a fair share of handling. I stripped all the paint and resprayed
with Crylon black "Textured Shimmer" aerosol paint. Looks respectable and sounds great.
Anyone needing help with this, please contact me. I might have a few
ready-wired replacement LCDs for sale if you're interested.
Good Luck!
Johan Forrer.
To my Home Page for contact details.
To my Guitar and Effects Page.
