Having quickly realised how fitting modern high contrast LED backlit displays to my TG/SY77 and K5000 have transformed the user experience and positively invited intense patch editing sessions thereafter I was determined to have a crack at retrofitting a similar display to the TG33.
It quickly transpired the original display was a 2x16 Hitachi HM44780 controller compatible character module with an almost standard pinout (there is a pin missing).
The cost of high contrast white on blue LED backlit FSTN displays of this form factor and interface standard has gone through the floor ever since they became very popular on the Arduino platform.
Having bought 4 displays for a mere £4 each on eBay I set about pulling the TG33 apart. This is a little tricky as, and is so often the case with Yamaha synths, there are quite a few layers of subassembly to remove before the display module is accessible.
To my delight the new LCD module had identical mounting positions, form factor and data cable positions to the original. Even more of a surprise were that both displays were the same depth. Often modern LCDs are deeper than their older counterparts as LCD backlights are more bulky than electroluminescent lamps (EL). In this case, however, the original was also LED backlit but things have moved on with LCD glass technology since then!
A quick look at the schematics revealed that the pinout of the old display almost matched that of the new one. The only difference was that (funnily enough!) there is no contrast (LCD voltage) pin on the original.
The new display has an LED backlight with an on-board current limiting resistor and so an external one is not required. Thus all that was necessary was to wire the cathode (K) pad to ground and the anode (A) pad to 5 volts.
I cut the cable header of the old display and temporarily wired up what I thought was the correct pinout to the new display.
On powerup I did indeed get the correct display but with the contrast way too low. After a bit of experimentation I was able to dial the contrast in line by adding a 3K9 resistor between pin 4 on the display and ground!
The new display very satisfyingly fitted in place of the original with the screws simply winding in place and everything lining up.
Hey presto a TG33 with a Cool Blue LCD - The Difference in Viewability is Remarkable!!
A Closer Look at the New Display Module and wiring:
The New Display in Situ:
I've tried to take a picture of the display running in situ but its just impossible to take a picture that even vaguely does the display justice - you can now read this thing on the other side of the studio!!
I will try it! Thanks! 