FZ tweaking
2004-04-21 by phonophobie
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: ___________________________________________________ "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 " ___________________________________________________