CZ-1000 lights and display will not turn off until power is disconnected.

[lulu_joe]

Hello, my CZ-1000 lights and display stay on after power is switched off, but the sound stops. When I unplug the power supply or remove the batteries the lights and display and on-off indicator light go out and stay out until the on button is pressed. Then the unit powers on and functions normally, and again when I press the button to turn the unit off, all the lights stay on. Any idea where to start troubleshooting? Thanks. JoeF.

[HELVETIA]

5 hours ago, lulu_joe said:

Hello, my CZ-1000 lights and display stay on after power is switched off, but the sound stops. When I unplug the power supply or remove the batteries the lights and display and on-off indicator light go out and stay out until the on button is pressed. Then the unit powers on and functions normally, and again when I press the button to turn the unit off, all the lights stay on. Any idea where to start troubleshooting? Thanks. JoeF.

Could be a switch problem  :

did you tried to reset the keyboard ?

The reset button (it's on the bottom and recessed; you'll need something long and skinny to poke it. Try that first.

 

[IanB]

If the sound is switching off, we know that the power switch is okay. The power board labelled M4152-MA2M signals to the CPU board (MA3M) via a cable bundle to shut down, so first of all check the continuity of all those connections while the boards are connected together (but the power is not connected) to see if they are all good. If it's a poor connection just unplugging and replugging both PCB connectors may fix it. It is possible that something has failed on the power board before the connector but I wouldn't think that particularly likely.

 

Here's the service manual. The same page as the power board schematic shows the On/Off switching timing diagram.

cz1000.pdf

CASIO_CZ-1000_SRV.pdf

Edited March 14, 2020 by IanB
Uploaded the wrong file!

[lulu_joe]

Thanks for the response. 

 I have puhed the reset.

 I will check the switch function I see there are several switches made on the switch board. Then look into tracing the connections from the switch to the board.

 I have replaced the relay because it was bad. I couldn't find the actual component and used a recommended replacement. But as far as I can tell it only handles audio.

 I  am concerned that I have burned something out from using a too powerful Wallwart(9v regulated but 2A). I have a 9V, 850ma one now.

 But, the symptom is actually as you describe. The main board isn't getting the signal to shut down and is running on memory backup power or something? I can change settings as if the unit was still on. JoeF.

[IanB]

The relay does only do audio. It disconnects the audio outputs to prevent a thump when you switch on and off.

The main board will be running on main power from the power board. The power supply board won't shut itself down until it gets an "okay" from the CPU board. So it looks like the CPU board isn't getting the switch off signal. It's not worth tracing connections from the switch to the board. We know that is working because it's controlling the relay okay.

The wall wart shouldn't be an issue. Current is not "pushed in", it is "pulled out" by the load. So as long as the rated current is high enough, that's fine. If you used a power supply rated at 100 Amps, the synth would still only pull whatever current it wants from it. Same as an LED table lamp won't take 100 Amps or whatever your mains supply is rated at.

Like I said, try disconnecting and reconnecting the cable connection between the power/amp board and the CPU board. That may be enough to solve a poor connection. Also, be very careful around the display connections as that is virtually unfixable if damaged.

[lulu_joe]

OK. Unfortunately, on the CZ-1000  these old ribbons are soldered. I did check the continuity on the pins. All is good. 

 I am looking at the schematics and next to the amp/power board are alphabetical test points(?). I have an oscilloscope but have never used it to troubleshoot. I have only played with it to look at audio signals for fun. One test point, “L” is NMI which looks like a shutdown signal on pin 8 of the ribbon. I am going to probe that and see if I can see it occur.

 The guest bed room is getting pretty cluttered as the tools get moved from my smallish workbench. Ha! Thanks again. JoeF.

 

[IanB]

Okay, so if you have an oscilloscope you can check those waveforms at the test points on the power board. The fault may be in some of the switching logic on that board also. Let us know how it goes!

[Jokeyman123]

Was the relay shorted, or open? Sometimes...you can trace a bad component to another nearby-if the relay only switched an audio signal, i am thinking there is a bad cap somewhere-much older equipment  will have dried-out caps. II this is so-a cap may be shorting or open and is either blocking a signal from the CPU or keeping voltage live long enough from other caps that may hold a signal line open long enough for the power to stay on.  Look for obvious leaky caps-or if you have a cap tester, check around if there are any in proximity to your data lines, or even in the power supply board. Just a wild guess.

[IanB]

Cautiously agree with Jokeyman, but tempered by warning not to go mad with recapping, which seems to have become a bit of a "universal solution" on the internet. Yes, old capacitors can go bad but it's generally high current rectifier smoothing capacitors that do so. A bulk replacement of capacitors can make matters worse, due to the risk of damaging old PCB tracks, not equivalent replacements, overheating other components etc.  Speaking just personally I bought a 4 track Tascam cassette portastudio off ebay which somebody had, it became clear, recapped, which was why none of it was working except channel 1 (I eventually fixed it, but what a pain!).

I think the relay may be a red herring as it doesn't participate in the rest of the circuit- it just switches the audio outs when it gets power (slugged by a capacitor which wouldn't affect the rest of the circuit even if it went bad). There is an electrolytic close to test point "A" - at the other end of the diode which is connected to "A" - which might cause a fault like this as it's intended to pulse a pair of gates configured as a flip flop. It's hard trying to diagnose faults when the PCB isn't in your hands though!

[HELVETIA]

13 hours ago, lulu_joe said:

Thanks for the response. 

 I have puhed the reset.

 I will check the switch function I see there are several switches made on the switch board. Then look into tracing the connections from the switch to the board.

 I have replaced the relay because it was bad. I couldn't find the actual component and used a recommended replacement. But as far as I can tell it only handles audio.

 I  am concerned that I have burned something out from using a too powerful Wallwart(9v regulated but 2A). I have a 9V, 850ma one now.

 But, the symptom is actually as you describe. The main board isn't getting the signal to shut down and is running on memory backup power or something? I can change settings as if the unit was still on. JoeF.

The ampere does NOT  kill  if you make the ampere to low   your power supply might get hot and fail also the keyboard won't runs well   but higher voltage   can kill   the keyboard sure !

For an example  if you got a power regulated 10 amp  9 volts power supply it will runs perfect the keyboard only consumes what is needed   .

BUT if you use    a 10 Amp .   and lets say  a 18 volts power supply ...the volts kills your keyboard  if not protected for over voltages . Ian B. did also explained this  I saw  .

[HELVETIA]

5 hours ago, Jokeyman123 said:

Was the relay shorted, or open? Sometimes...you can trace a bad component to another nearby-if the relay only switched an audio signal, i am thinking there is a bad cap somewhere-much older equipment  will have dried-out caps. II this is so-a cap may be shorting or open and is either blocking a signal from the CPU or keeping voltage live long enough from other caps that may hold a signal line open long enough for the power to stay on.  Look for obvious leaky caps-or if you have a cap tester, check around if there are any in proximity to your data lines, or even in the power supply board. Just a wild guess.

I found more times defective zener diodes  but hard to tell  from a chat lol 

[lulu_joe]

Hello all, I have been making progress in that I am

learning how to trace and test with my Oscope. I have found that at test point “L” the state never goes low once high. So, I traced back to location J which passes the test. But, at test point K the voltage goes high as it should when the unit is switched off but it never falls back down.

 I am thinking I should remove caps in this vicinity and check them? Thanks. JoeF.

Edited March 16, 2020 by lulu_joe
Mispell

[IanB]

Interesting... before you go ripping out caps, what's happening at A and B and also the junction of the diode, capacitor and 100R resistor to the right of Point A on the schematic?  That capacitor (labelled 16V 10u) and the 10V 22u one to the right of "J" both might be candidates here. Or something else entirely, heh.

*edit* Also are D and E flipping as they should?

Edited March 16, 2020 by IanB

[Jokeyman123]

And the diode-could be burned out-check its forward and backward voltagee-one should be high and reverse polarity low-or the other way around-I forget which is which from anode to cathode-but should not be the same voltage from one polarity to the reverse. current and voltage should be "closed" for one polarity and "open" for the reverse polarity. so voltage should be high-I usually find around 3 or so volts in one direction and .7 is standard or sometimes lower in the opposite direction. Zeners will have slightly different values, but yes zeners can go in a supply line. If a diode is bad, it will keep a data line to a plus charge on that line instead of pulling it down to ground-the cpu will read a positive voltage instead of no voltage-and will keep the signal pulled up-this might account for the CZ not turning off-it is still seeing at least one data line as plus voltage and is responding as if the CZ is still on-again, just a guess.

[IanB]

Just looking at the circuit again, to contradict my earlier statement about the power switch; it is double pole (two switching elements) and one pole is controlling the base of T7, so maybe the switch is suspect after all. Check what is happening on the white wire connected to it and with the power off check if continuity is making and breaking across white and black (or red, black and red are connected together at the switch). I'm beginning to suspect the Auto Power Off circuit here. For completeness, check if anything changes with the APO switch both on and off.

[HELVETIA]

37 minutes ago, IanB said:

Just looking at the circuit again, to contradict my earlier statement about the power switch; it is double pole (two switching elements) and one pole is controlling the base of T7, so maybe the switch is suspect after all. Check what is happening on the white wire connected to it and with the power off check if continuity is making and breaking across white and black (or red, black and red are connected together at the switch). I'm beginning to suspect the Auto Power Off circuit here. For completeness, check if anything changes with the APO switch both on and off.

 

37 minutes ago, IanB said:

Just looking at the circuit again, to contradict my earlier statement about the power switch; it is double pole (two switching elements) and one pole is controlling the base of T7, so maybe the switch is suspect after all. Check what is happening on the white wire connected to it and with the power off check if continuity is making and breaking across white and black (or red, black and red are connected together at the switch). I'm beginning to suspect the Auto Power Off circuit here. For completeness, check if anything changes with the APO switch both on and off.

Yes I suspected the switch   in the first place as they keyboard is an old model  ... might be also the T7 if it is used as electronic switch but i do not have the schematics just what i remember from that keyboard  . .    

[IanB]

@HELVETIA The schematics are in the service manual I posted above, if you're interested in taking a look.

[HELVETIA]

10 hours ago, IanB said:

@HELVETIA The schematics are in the service manual I posted above, if you're interested in taking a look.

tnx got the schematics   .

 

Think it's a mechanical switch  he should  check  this 1  first  if he not did already ...   after many uses it

 often fails !

 

[lulu_joe]

Hi all. Thanks so much for the advice. Workday so I only had a bit of time to look at my synth. But, I checked the switch using continuity and it is fine. It is not the switch. I will carefully read everyone’s comments and make the checks at points A and B. Then report back as soon as I can.

 Is there any ez check for caps in circuit or do I have to remove them to check them? Diodes? JoeF.

[lulu_joe]

To answer the question about the audio relay. It was faulty. Not completely open or closed. The volume would fade in and out as you played the keyboard. If you knocked the pcb you’d here crunching distortion. The new relay fixed all that.

 I think it’s a component around T6 or T7.  It’s the signal from the 4011 pin 11 that is not going low. The logic from input pin 12 and 13 is not right.

 I don’t understand how the transistor logic works well enough to know exactly whether it’s a diode or rc cell. JoeF.

[Jokeyman123]

You can check diodes soldered in place-with power off-resistance should be high in one direction, low in the other-the diode has a cathode and anode. Most times these do not become defective-but it is possible as it functions similar to a fuse-but in one direction only. If you get the same resistance measurements when measuring anode/cathode, cathode/anode then the diode is bad-zeners included. with voltage supplied-circuit on-voltage will be high in one direction, low in the other, depending on what else is connected to the diode circuit. A cap can also be resistance checked in circuit-at least to see if it is "open" or shorted. A capacitor tester is better-but caps must be removed-a cap tester can be gotten fairly inexpensively-I think i bought mine for less than 20.00 US. diode checking in circiuts cn be tricky.  Read this by Fluke.....

 

https://www.fluke.com/en-us/learn/best-practices/test-tools-basics/digital-multimeters/how-to-test-diodes-using-a-digital-multimeter

[HELVETIA]

9 hours ago, lulu_joe said:

To answer the question about the audio relay. It was faulty. Not completely open or closed. The volume would fade in and out as you played the keyboard. If you knocked the pcb you’d here crunching distortion. The new relay fixed all that.

 I think it’s a component around T6 or T7.  It’s the signal from the 4011 pin 11 that is not going low. The logic from input pin 12 and 13 is not right.

 I don’t understand how the transistor logic works well enough to know exactly whether it’s a diode or rc cell. JoeF.

if 1 or more of the  transistors are defective its won't send send a low or high to the  40 11      but you have to remove the transistor to test it right  ...for diodes i cut 1 side for to test and solder it back if ok  ,,,,caps elco's  remove ...  test or replace them right away  ....my best bet is a transistor or diode died .The CZseries are about 20 +years old and not very well build  if you got any time a wrong voltage   higher as 9 volts some electronics  dying easily in this keyboard and should be cheaper and easier to replace the keyboard  if you find  one  .

But you said  for the rest everything is working normally  ...if so  I would just pull the power cord without the possibility  to kill the keyboard  !

 

[HELVETIA]

5 hours ago, HELVETIA said:

if 1 or more of the  transistors are defective its won't send send a low or high to the  40 11      but you have to remove the transistor to test it right  ...for diodes i cut 1 side for to test and solder it back if ok  ,,,,caps elco's  remove ...  test or replace them right away  ....my best bet is a transistor or diode died .The CZseries are about 20 +years old and not very well build  if you got any time a wrong voltage   higher as 9 volts some electronics  dying easily in this keyboard and should be cheaper and easier to replace the keyboard  if you find  one  .

But you said  for the rest everything is working normally  ...if so  I would just pull the power cord without the possibility  to kill the keyboard  !

 

Try to replace the T7  

[IanB]

I think T7 is not the culprit. Looking at the schematic and diagram, it is pulling up correctly but then the voltage at K does not drop. K only drops when the voltage Vdd falls, which means the Vdd regulator is not switching off. So far as I can tell without the board in front of me (my, this is one complicated power supply, heh) is that point F needs to pull low to switch off the power, which is reflected by Vdd falling. F should pull down after 5ms from the power off "command".
 

@lulu_joe what is point F doing on your oscilloscope?

F should pull down the base of T5 in the Auto Power Off circuit and switch off the regulators. I think.

[HELVETIA]

5 hours ago, IanB said:

I think T7 is not the culprit. Looking at the schematic and diagram, it is pulling up correctly but then the voltage at K does not drop. K only drops when the voltage Vdd falls, which means the Vdd regulator is not switching off. So far as I can tell without the board in front of me (my, this is one complicated power supply, heh) is that point F needs to pull low to switch off the power, which is reflected by Vdd falling. F should pull down after 5ms from the power off "command".
 

@lulu_joe what is point F doing on your oscilloscope?

F should pull down the base of T5 in the Auto Power Off circuit and switch off the regulators. I think.

That is why I think he just  pull the power plug as i think it's not worth the troubles lol