--- In CZsynth@yahoogroups.com, "Scott Nordlund" <gsn10@h...> wrote:
> >Hi everyone,
> >This is my first post here. I recently picked up a second hand
CZ5000.
> >I have been trying to get it working. I noticed that a couple of
the
> >fuses on the PCB near the power supply in were missing so I have
> >replaced those with the correct value and checked the other fuses.
> >All the boards seem to be in pretty good shape with no sign of
> >missing, broken or fried components. Also the fuse thing on the
> >bottom is set to the correct voltage (240V for the UK).
> >At the moment when I turn the thing on none of the led's on the
> >control surface (including the mod/pitch wheel led) come on and the
> >only thing that comes to life is the lcd display which faintly
shows
> >a row of pixel blocks where presumably the edit parameters and
patch
> >name should be. If anyone has any speculative ideas about what is
> >wrong with the synth I would love to hear them as I am keen to try
> >and fix it. Even if you think that it is beyond repair please let
me
> >know. If it is truly screwed then I will happily take it to pieces
> >and send out any spares that anyone here might need ie:
> >buttons/switches etc.
> >Also what is the battery compartment for on the bottom of the
> >synth..is this to save patches in the memory when it's disconnected
> >from the mains?
> >Thanks for reading this...I'd love to hear from you. *NK
>
> Yes, the battery is for patch memory.
>
> The first thing you do for a broken synth is check all of the
connectors to
> make sure they're not loose or corroded and reseat all of the
socketed chips
> (carefully), then do a hard reset. If you can manage, check the
power
> supply. After that it gets a bit more difficult...
>
> >Casio CZ 5000 1985
> >No function,LEDs or LCD display
> >The only convenient 0V point for the TTL I could
> >find was the -ve pin of the ps bridge rectifier.
> >No 5V for the TTL. It looks as though the keyboard had been
> >dropped as the large electrolytic on the ps had moved and
> >consequently the track continuity to the 5V regulator part of
> >the ps was broken under the capacitor pin,not obvious at al.
> >With all 3 connectors unplugged and PA order on main pcb
> >not the ps end which is different order.
> >PA 0,15.3,-16,0,5.6,0,5.2,0,5.2
> >PC 0,0.03,5.2
> >PD 0,16,15.3,0,0
> >
> >I found the above on a website...it sounds almost identical to my
> >problem...can anyone spell it out a bit more as to where i should
be
> >looking for this capacitor pin..as i am no expert in these maters.
> >Any help would lift my day.thanks.....
>
> He's saying..he tested the power supply (using the pin of the
bridge
> rectifier as a ground point) and found that there was no +5V supply
for the
> digital logic (generally power supplies generate different voltages
for
> different parts of the device to use- for example +5V for digital
parts,
> +12V, and -12V for analog). The circuit board trace under the
largest
> capacitor was broken. If you want, you can look on the bottom of
the power
> supply board to see if anything is messed up, but as you said
there's a line
> on the LCD, I would imagine that the digital circuits are getting
power.
> Anyway it's pretty unusual to have a broken trace like that..
Thanks for your help Scott...You are right..my CZ probably isn't
broken the same way as his, but the symptons are pretty close...the
LCD display on mine is very faint when i power up so maybe the
digital circuits are not getting enough power..Is there a good
website anywhere with tips on the basic tests you mention like re-
setting chips and testing components...I have a couple of testers..a
logic? tester (has a screwdriver tip and two contacts for different
readings (voltage tests i think). the other has a crocodile clip at
one end and a probe with a bulb in. As you can tell I am no expert at
this stuff..would like to know what i'm doing before i start mucking
around inside that thing and making it more screwed up.
thanks for reading
*NK
>
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