Casio CZ/ VZ/ FZ - Pro Series

On Wed, 2010-12-08 at 03:17 +0000, davidmochen wrote:
> Hi all,
> 
> I own a CZ1 with an almost dead EL backlight. 
> 
> What I would like to know is:
> 
> 1) is there any chance to hack the inverter circuit/transformer so
> that it could feed a couple LEDs which I plan to place besides the
> LCD? (more details on that below). AFAIK the input to the inverter is
> VDC, so maybe disabling the transformer and doing some extra stuff
> would get the point.

No, because the inverter takes a low voltage and steps it up to a couple
of hundred volts to drive the EL backlight and LEDs need about two
volts ;-)

Not only is it a bad idea to modify the inverter, it's not even
particularly necessary.

> 2) if 1 above is a no-no, where can I get appropriate current from for
> driving a couple bright LEDs? I've seen some posts where a brand new
> display with built-in LED backlight was retrofitted into non-backlit
> models like CZ1000. The on switch was mentioned, but I also saw that
> also pins 1 and 2 of the LCD can be used for that. Also, could I
> disable the inverter circuit so as to save some power?

Pick up a DC supply from just about anywhere, including as you say the
power leads to the LCD.  Wire the LEDs up with a suitable
current-limiting resistor which you can work out from the forward
voltage and current of the LED and the supply voltage.  Or, just run it
off the 5V rail with a 220 ohm resistor for each LED, that'll get you
about right.  Don't go much below about 100 ohms unless you're using a
very high-power LED, or you'll cook it.  Above about 680 ohms chances
are it'll be a bit too dim.

> My idea is to keep the existing LCD and fit it with a custom
> backlight. I've been doing some tests with a tiny rectangular piece of
> acrylic sanded on one side so as to diffuse light. I placed it where
> the EL foil used to be and lit it with a small LED lantern. Light gets
> effectively across it and the LCD gets softly lit so I think if I
> placed two strong-enough LEDs at both sides of the acrylic I would get
> a nice backlight.

You can get EL films for other gear like the Akai samplers.  I bet if
you send the old film to one of these guys on eBay they'd cut you a bit,
or just sell you an Akai backlight to cut up yourself.

> I have only very basic electronics knowledge but am not afraid of
> soldering stuff. :)
> 
> Thanks very much in advance for any help.

Well, you like old synthesizers so you're going to need to learn to
repair them some day ;-)

Gordon MM0YEQ