Yamaha TG33 - Cool Blue LCD Retrofit for £4!!

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Yamaha TG33 - Cool Blue LCD Retrofit for £4!!

Postby HideawayStudio » Wed Mar 11, 2015 7:33 pm

The TG33 has been a secret weapon on mine for many years - I have quite a soft spot for this underrated little gem but what has continually annoyed me from day one has been the terrible viewing angle of the original LCD display which made it all but impossible to read from some positions.

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!!
Image

A Closer Look at the New Display Module and wiring:
Image

The New Display in Situ:
Image

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!!
Last edited by HideawayStudio on Thu Mar 12, 2015 9:07 am, edited 1 time in total.
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Re: Yamaha TG33 - Cool Blue LCD Retrofit for £4!!

Postby synthroom » Wed Mar 11, 2015 8:20 pm

As always, very nice!
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Re: Yamaha TG33 - Cool Blue LCD Retrofit for £4!!

Postby synthroom » Thu Mar 12, 2015 7:21 am

DO you have any recommended LCDs for the EII?

Also, How do you tell when the LCD has aged beyond it's useful life vs the backlight being out? Just a matter of brightness of the backlight? My EII backlight is dim but still shows blue light, but it looks to me that the LCD is not as contrasty as it once was.
Image
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EII, Emax II, Minimoog, ARP 2600, P-5 Rev.1 (broken...), Pro-One, Crumar Performer, K1m, K5m, MS-2000B, Virus KC, a few other things.
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Re: Yamaha TG33 - Cool Blue LCD Retrofit for £4!!

Postby HideawayStudio » Thu Mar 12, 2015 9:07 am

synthroom wrote:DO you have any recommended LCDs for the EII?

Also, How do you tell when the LCD has aged beyond it's useful life vs the backlight being out? Just a matter of brightness of the backlight? My EII backlight is dim but still shows blue light, but it looks to me that the LCD is not as contrasty as it once was.
Image

The EII LCD has a high voltage electroluminescent (EM) backlight driven by a small invertor which is notorious for going dim with age (sometimes the invertors fail too). I doubt any of the original EII displays would be correctly lit by now. It is rare for the display itself to degrade and often its just that older designs were less capable of producing high contrast images.

It is often pretty easy to replace the EL backlight on such displays but I've often found the results are a little disappointing. Display technology has really moved on since then and perhaps our expectations are higher than they used to be.

I suspect some displays fit the EII better than others but I seem to recall I had a bit of a battle fitting a modern LED backlit LCD module to the EII not least because none of the mounting holes were in the same position and the new display was considerably smaller but also rather deeper. I have a vague memory I might even have had to drill a new hole through the front panel pcb to pick up on one of the mounting holes.

Aside from making the display mechanically fit the main issue I had was that although so many 2x16 character displays are broadly compatible (Hitachi HM44780 equivalent LCD controllers) their timings are slightly different and an old gremlin came up that I've encountered before. When the display was hooked up sure enough it came up but only one line of text appeared and the other line was full of garbled characters. This was due to the LCD interface timing in the EII being somewhat marginal and although the original slower display was ok with this a modern display with no doubt faster silicon was reading off the bus at not quite the right time.

To my relief I managed to overcome this by slugging one of the control lines with a small capacitor.

My guess is that this anomaly would appear with at least some other modern displays.

On the mechanical front I seem to recall that one of the issues is that, unlike the TG33 where the LCD is wired in on long leads and therefore the position of the connectors is not so critical, the EII LCD module connected to a pin header very close to the LCD module on the front panel pcb. Although it may well be possible to find a suitably nice LCD module with the header in exactly the right place I didn't have this luxury so I ended up desoldering the header and fitting a set of small wires mapping the two headers correctly.

One advantage of retrofitting an LED backlit display to the EII is that the often noisy EL backlight invertor can be removed.

In that case I fitted a black on yellow display which looks a little nicer than this in reality:

Image

Image

Image
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Re: Yamaha TG33 - Cool Blue LCD Retrofit for £4!!

Postby Virgule » Fri Mar 13, 2015 12:31 am

That looks good....I'm thinking of having the display on the Yamaha FB-01 changed. After owning several units, I'm decidedly fed up with the red/orange glow.

I don't know how hard or easy it would be to find a compatible replacement (16x1 characters).
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Re: Yamaha TG33 - Cool Blue LCD Retrofit for £4!!

Postby HideawayStudio » Sat Mar 14, 2015 10:32 am

Virgule wrote:That looks good....I'm thinking of having the display on the Yamaha FB-01 changed. After owning several units, I'm decidedly fed up with the red/orange glow.

I don't know how hard or easy it would be to find a compatible replacement (16x1 characters).


It is quite possible the new TX7 Cool Blue retrofit LCD can be persuaded to fit and work in the FB-01:

http://www.ebay.co.uk/itm/Yamaha-TX7-Co ... 1e9ad998e8
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Re: Yamaha TG33 - Cool Blue LCD Retrofit for £4!!

Postby mstsfreak » Sat Mar 28, 2015 9:31 am

Can you tell me what type and brand of display you used and how to wire it? I also need to replace the lcd of my TG33, because it is hardly readable anymore.
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Re: Yamaha TG33 - Cool Blue LCD Retrofit for £4!!

Postby HideawayStudio » Sat Mar 28, 2015 10:15 am

mstsfreak wrote:Can you tell me what type and brand of display you used and how to wire it? I also need to replace the lcd of my TG33, because it is hardly readable anymore.

Here are some more details on what I used and how I wired it up...

LCD Module Available on eBay in either White on Blue or Black on Yellow:

http://www.ebay.co.uk/itm/201055413804? ... EBIDX%3AIT

TAKE NOTE OF PIN 1 END OF ORIGINAL DISPLAY BEFORE REMOVING HEADER:

Pin Mapping from TG33 display harness to new display:

TG33 (13 pins) New LCD (16 pins):
1 ---------------> 1
2 ---------------> 2
3 ---------------> 4
4 ---------------> 5
5 ---------------> 6
6 ---------------> 7
7 ---------------> 8
8 ---------------> 9
9 --------------> 10
10 -------------> 11
11 -------------> 12
12 -------------> 13
13 -------------> 14

Also wire over with small hookup wires:

1 (GND) 16 (Backlight Cathode)
2 (5V) 15 (Backlight Anode)

No limiting resistor required for backlight - already on-board display.

Contrast Setting:

Wire LCD pin 3 to TG33 pin 1 (GND) via 3K9 resistor to set correct contrast.

IMPORTANT:

Insulate along top of solder pads with insulation tape wrapped around top edge of display pcb before mounting new display to prevent solder pads and wires shorting to top chassis rail.

Mounting holes identical position to original - retain original screws.

* * * PLEASE UNDERSTAND ANYONE WISHING TO UNDERTAKE THIS RETROFIT DOES SO AT THEIR OWN RISK * * *
Last edited by HideawayStudio on Tue May 05, 2015 8:07 pm, edited 1 time in total.
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Re: Yamaha TG33 - Cool Blue LCD Retrofit for £4!!

Postby mstsfreak » Sun Mar 29, 2015 12:11 am

Thanks for the information. Now i can finally make my TG33 more readable. 8-)
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Re: Yamaha TG33 - Cool Blue LCD Retrofit for £4!!

Postby Trancer Spacey » Mon Apr 06, 2015 11:58 am

Just a question, because I'm totally new to this stuff: when I want to buy a display like this, which one should I select? I mean there is the option "with headers" (with straight pins, right angle pins,... and so on)

I guess I need the one without headers, am I right?
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Re: Yamaha TG33 - Cool Blue LCD Retrofit for £4!!

Postby Trancer Spacey » Mon Apr 06, 2015 11:59 am

Can I use such a display like the one which is posted here for the Casio CZ-1, too?
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Re: Yamaha TG33 - Cool Blue LCD Retrofit for £4!!

Postby mstsfreak » Tue May 05, 2015 6:19 pm

Built the display in, but i have no text in the display, could this be a contrast setting? I put in a trimming resistor between pin 4 and 1 of the display but i don't see any text.
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Re: Yamaha TG33 - Cool Blue LCD Retrofit for £4!!

Postby HideawayStudio » Tue May 05, 2015 8:08 pm

mstsfreak wrote:Built the display in, but i have no text in the display, could this be a contrast setting? I put in a trimming resistor between pin 4 and 1 of the display but i don't see any text.


Sorry - very slight typo in my original pinout - should read:

Contrast Setting:

Wire LCD pin 3 to TG33 pin 1 (GND) via 3K9 resistor to set correct contrast.

ie. not pin 4.

Hopefully that should fix it.
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Re: Yamaha TG33 - Cool Blue LCD Retrofit for £4!!

Postby mstsfreak » Wed May 06, 2015 9:56 am

HideawayStudio wrote:
mstsfreak wrote:Built the display in, but i have no text in the display, could this be a contrast setting? I put in a trimming resistor between pin 4 and 1 of the display but i don't see any text.


Sorry - very slight typo in my original pinout - should read:

Contrast Setting:

Wire LCD pin 3 to TG33 pin 1 (GND) via 3K9 resistor to set correct contrast.

ie. not pin 4.

Hopefully that should fix it.



Aha! :o I will try it! Thanks! :drinks:
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Re: Yamaha TG33 - Cool Blue LCD Retrofit for £4!!

Postby zoomtheline » Wed May 06, 2015 12:05 pm

Hey Hideaway.
Are you the chap on ebay selling backlight replacements? If so, i'm localish to you. Have you ever done a DX100?
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