Casio CZ/ VZ/ FZ - Pro Series

Hi,
I have to replace the Backlight Display of the FZ10M. I just found a
review from someone saying that the problem will come back soon. Maybe
someone could comment on that:

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"Graham Meredith  a hobbyist user from Australia writes:
2141*graham_meredith@... (remove 2141* from address to contact)
****** Design fault info ******

Read this all you FZ-1 owners who are having mysterious crashes of
your sampler, or corrupted or or glitching samples, I figured it out a
long time ago, here's your fix:

I bet there must be very few FZ-1 and FZ-10M's still around by now,
that still have the screen backlight working. I replaced mine twice.
This is a hardware design fault in the fluorescent backlight panel
behind the display screen. The backlight is cheap ($15) but I doubt if
you can get them from Casio now. Maybe someone can find an alternative
supplier. They're faulty, any way. Or perhaps the circuit that drives
them.

What happens is that over a period of time (about a year) the
backlight gradually fades. Eventually it doesn't work at all. What is
happening at this point, or sometime after, is it begins to increase
in its internal electrical resistance.

The circuit that powers it is a 90 volt DC supply, that is created by
using one of the 12V supply rails on the main circuit board, which is
passed through an oscillating transistor, then a small step-up
transformer from 12V AC to 100V AC. A regulator circuit then converts
this to about 90V DC. This powers the backlight.

What happens is that as the backlight fades, its internal resistance
rises. The oscillating transistor that boosts the voltage to 100V AC
is designed to operate with a specific load from the backlight
attached to it. If the resistance increases it, it basically becomes
an open circuit, and causes the oscillating transistor to oscillate
out of control. This is heard as a high pitched audio buzz coming from
the display (not through the audio outs of the sampler). At this point
the screen goes all blurry and the sampler crashes, and the noise will
continue. The machine needs to be switched off.

My suspicion is that this type of backlight has a design fault, or the
power supply voltage has been designed too high for this particular
brand or type of backlight.

**** The Remedy ****

You have to do 2 things:

1) disconnect the backlight and remove it (easy).

2) Unsolder and remove the oscillation transistor and also the small
transformer associated with it from the circuit board. (a bit more
difficult, but any friend with good soldering and electronic kit
building skills can do it).

I have the electrical schematics for the FZ-1, anyone who wants them
can email me and I'll scan them and email them for you, to help with
fixing the circuit.

Comments:

A fantastic retro sampler, really easy to use. I bought mine back in
1992, and I was a complete novice to sampling. But when I bought it,
it was a whole week before I needed to open the user manual! And that
was to to complex cross-fade stuff. It was that easy. I love this
thing, except for the display issue, which isn't a problem now that I
disabled the backlight.Graham "
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