Casio CZ-101 - 5 seconds to live (boot/power up problem)

Pulling out your hair? Don't know what to do or where to go? Ask in here.
Forum rules
READ: VSE Board-Wide Rules and Guidelines

If your Help request has been solved, please edit your first post in order to select the Image Topic Icon to let others know your topic has been solved.
Post Reply
User avatar
soamatic
Newbie
Newbie
Posts: 1
Joined: Tue Jul 20, 2021 1:47 pm
Band: Ivatu

Casio CZ-101 - 5 seconds to live (boot/power up problem)

Post by soamatic » Tue Jul 20, 2021 2:44 pm

Hi everyone, I really need some help with this one

Problem: CZ-101 power up immediately after dc jack plugged in (regardless of power switch position). All LEDs lights up, the screen is blank and nothing happens. Then after about 5 seconds lights rapidly start to fade out and in the end only dim pulsation is left. To repeat this sequence I need to wait some time because if I unplug dc jack and then immediately plug it back there will be only dim pulsation

History(Legend): I got this synth to repair from a friend of mine. The guy who sold it (to a friend) claims that synth was in working condition last time he checked (5 years ago). Inside I can see traces of battery leak, but all boards are clean (+/-) and marker marks all over the place so I suppose there was leakage and repair before synth got in hands of that guy

Testing: First thing, as I mention before, synth power up regardless of power switch position. More than that, if I completely desolder power switch board (M4152-CN5) I got the same results. Power switch by itself working as it should. DC jack is a right one, polarity and V checked. Ribbon cable between boards MA2M and MA1M is fine.

when i plugged in dc jack
- I can hear relay click - T4 emitter reads 5v (VDD line) and T11 emitter reads 4.1v (VBR line), seems fine - after 5 seconds relay clicks again, LEDs start to fade out and T4 emitter begin jumping between 1v and 6v, T11 emitter stay the same

when i plugged in dc jack but previously desolder MA2M board
- no relay click - T11 emitter reads 4.1v but T4 going in cycle from 5v to 0v (when p.s. in "on" position cycle moves faster)

By this time I replace T2, TC4066 and 2200µ 16v, 1000µ 6.3v, 47µ 16v capacitors. Next step will be full recap.
I hope that maybe someone here can give me good advise or hint where to look to fix this problem. I read every topic on the web regarding CZ-101 repair (a lot of useful info) but still in doubt where to look.


P.S. sorry for bad english, I tried to be understandable

User avatar
meatballfulton
Moderator
Moderator
Posts: 6204
Joined: Wed Apr 13, 2005 9:29 pm
Gear: Logic Pro X

Re: Casio CZ-101 - 5 seconds to live (boot/power up problem)

Post by meatballfulton » Tue Jul 20, 2021 3:49 pm

First thing to try is put some batteries in it and see if it works.
I listened to Hatfield and the North at Rainbow. They were very wonderful and they made my heart a prisoner.

User avatar
crochambeau
Newbie
Newbie
Posts: 5
Joined: Mon Mar 08, 2021 6:25 pm

Re: Casio CZ-101 - 5 seconds to live (boot/power up problem)

Post by crochambeau » Fri Jul 23, 2021 12:13 pm

I've seen cleaner schematics than the CZ-101 one I am currently looking at (as it happens, I too have a CZ-101 in need of attention, though mine doesn't power at all if memory serves).

My interpretation of the power switch function is that it supplies a logical high, which in turn activates pass characteristics of transistors in the power supply section to provide for the entire circuit. So, in short, the power switch does not appear to *interrupt* system voltage when off (in the classic way), meaning if any of those transistors that would normally await a logic high to turn on is shorted into passing current all of the time, that current will spill into the next node, regardless of power switch state.

If this were my puzzle, I would scrutinize all of the actives in the power section for shorted conditions before replacing all of the capacitors.

(assuming the previous "check with batteries" suggestion did not bear fruit - by all means do a battery test first, it's easy and non invasive)


Last bumped by soamatic on Fri Jul 23, 2021 12:13 pm.

Post Reply