CZ-101 Troubleshooting at various stages!

[momo]

Hey There,

I hope I am lucky with reviving this thread... ^^

My beloved CZ-101 just died on me two days ago. It had a similar problem to the one described on here. If I turned the power off, all LED's and Sound went off and only the screen stayed on. I got the CZ like that, did not mind it too much and now it wont power on any longer...
Sadly I am new to electronics, I do have a multimeter and do know how to check Volts and Resistances but the multiple voltages across the PSU-Board make it particularly hard to know where to measure what... I have to admit, my schematic reading skill are not that good

I can see that 8.9V come in at the DC Jack, and I was able to realign emitter T11 back to 4.3V, sadly still nothing...
Thus I remembered this thread and thought I might be good to just replace the IC that the OP had replaced in his procedure...
Is there a way to test if my 4011 is still working without a oscilloscope? Do I risk anything by replacing it? Would it seem possible that a faulty 4011 could be the cause that my CZ wont power on at all?

Edited March 1, 2022 by momo

[IanB]

@momo Well the short answer is, try replacing it and see if it works. It can't make things any worse. If you do, put the IC in a socket rather than soldered to the board. As far as testing goes, if you look back up the thread you'll see that it's a quad NAND gate, so for each of the gates, taking both inputs HIGH should make the output LOW. It does sound like a similar power board problem. I'd try this and see if it works.

[momo]

Alright, I am right with the assumption that the CD4011BE is a descendant of the CD4011B and thus can also be used?
Will order that one chip and hope for the best... Would be shame if I cannot revive it

Edit: Just checked and I have a CD4011BPC as a leftover this one should also work, shouldn't it?

Edited February 21, 2022 by momo

[momo]

The CD4011BPC did not resolve the issue, still no cz for me 😕 dont know if it is worth to try a BE?!

 

[IanB]

They should be interchangeable, those letters are various options like whether it's lead free, etc. These chips can be damaged by static so it's possible your replacement was also faulty, you could test it on a breadboard but it's probable the fault is elsewhere, so I doubt very much ordering the BE (that's the standard designation, it actually just means buffered input which are standard) will help. There's a lot of discussion in this thread of what voltages should occur where during startup etc, I know it's tedious but I would advise reading the whole thread and see if it's any help. Otherwise we're starting from scratch again

[IanB]

So  anyhoo, looking at the service manual I think a first step would be to check the voltages at the marked test points on the power board. Most of these can be checked with a multimeter, for instance point D should go high when you switch on and stay on until you switch off, point E should go low, F should go high when you switch on and off (after a 5ms delay, too short for you to see) when you switch off. Measure the voltages at each of these test points with your multimeter and make a note of what they do as you switch on and off, and report your results back to us

 

Point "G" is a really useful test point as it's the output of the voltage regulator.

 

Also check you've got power coming in and out of the power switch etc

Edited February 22, 2022 by IanB

[momo]

Finally...Had to wait 24h to make this post, seems like I am limited to 2 posts within a day.
Thanks for the clarification, I opened the CZ up again and checked as you recommended. 
First I went with 'D' on the 40H000P. There I measured with PIN 6 and 7 (GND). The Volts do not change no matter if it is on or off and stays at around 3,67V. Same goes for measuring point 'E' on the same IC with pin 8 and 7. Went on and checked point 'F' on 74HC04, here I measured with pin 12 and 7 and got the same results as on 'D' and 'E', no changes with both switch positions. Voltage stays at around 3,6V.
Thus I went on to check the Power Switch... Here I measured with GND of the DC input socket together with each of the 6 connections on the PSU-Board for Y-GND I got 0V for ON&OFF, R-GND has 8,9V for ON&OFF, BK-GND is at 0V for ON&OFF, BL-GND 0V ON&OFF, W had 8,9V for ON and 0 for OFF and BR seem to be a bit unstable for ON - somewhere between 1,6-2,1V and for OFF it stays at 1,6V 

I do not know which values are expected for the Power switch but these seem to off, don't they? I can measure 8.9V at the DC in Jack, so Power seem to come in.

[IanB]

Thanks momo, just looking at the circuit BL should be physically connected to R, if you look at the schematic you can see that on the power switch's little board M4152-CN5M on the lower right of the drawing. So blue should be the same voltage as red. Can you check continuity between them, with the power disconnected, then measure the voltage again with power off and on?

 

Also all these middling 3.6V measurements suggest to me the chips aren't powered and are just floating.

[momo]

Hey Ian,

Just made the continuity test for BL<->R on the switchboard as well as the on the MA2M both cannot be read at a fixed value, it 'slowly' moves up and down from kOhm to mOhm and back. From looking at the schematics I would've expected 0 Ohms due to the direct connection without any resistors in place, is this assumption right?

 

Regarding the Volts between BL and R it measures at 8.9V for both switch positions, ON and OFF

Thanks btw for all your help already, feels like I'm securely learning new stuff

Edited February 23, 2022 by momo

[IanB]

@momo Yes, according to the schematic there should be 0 ohms. It seems to me (anyone else reading this, am I right?) that the sole purpose of BLue is to act as a pulldown via the 100R resistor (connected to ground) which enables the Power On pulse at A etc to function. The White wire ultimately connects to there, if you trace the diagram. As far as I can see it discharges the capacitor that does the pulse. The thing to do now would be to trace out what is happening with R and BL on the little CN5M board. You might just have a bad solder connection. Feel free to post explicit pictures of the board  

[momo]

Had to wait again for giving you this answer, and I think my current rank won't allow me to upload pictures on here... so here is a WeTransfer link for a file with the pictures in it.

https://we.tl/t-pelDx2LdCf

 

I retouched all solder points on the Power supply board as well as on the switching board, sadly without any luck...
This makes me wonder if maybe the two ds135d diodes may be faulty. The don't look clean anymore, there are black sprinkles on the connectors (to be seen on a picture in the Wetransfer folder): Measuring them is pretty hard as well, on the solder side each measure with .1 ohm and if measured on the component side I get quite jumpy values.
 

[Brad Saucier]

Please keep posting.  You will have full member status soon.  Positive reactions given and received will help speed it up.  

[momo]

Thanks for heads up @Brad Saucier! Hopefully this post will score me the remaining two points that are left ^^
Regarding the Diodes, as these are not obtainable any more, I have two 1N 4001 laying around I suppose these cannot be used as replacement for the DS135D? 


I am still restricted to two posts a day, but now I can still edit my old post ^^

@IanB, I measured the resistance from Red on the power board to the solder point in the star that is consisting of two pads being connected. Here again I get jumpy values, it does not stay constant at all jumping from mOhm->Ohm->kOhm
Most of the time it stays in the kOhm realm!

Edited February 23, 2022 by momo

[IanB]

I don't think the diodes are the problem, they're just steering the battery supply and we know power is coming in okay. 1N4001s would be fine, they're just rectifiers, but ignore them. Something isn't making sense: reading back, the V+ can't get onto BLue if it's not connected to Red, so either your voltage measurement or continuity measurement must be incorrect. With the machine disconnected from power, test resistance from Red (either end) to that star point of circuit traces we can see in the photos on the power board. You should get about 100 ohms, and if so we can discount problems with the power switch.

 

I'd generally advise against over-enthusiastically swapping components and resoldering things as this can introduce new issues on top of the old one(s). A while ago I bought a Fostex 4 track on Ebay that somebody had decided to replace all the capacitors in and rendered it completely non-functional!

[momo]

Hey @IanB, I measured the resistance from Red on the power board to the solder point in the star that is consisting of two pads being connected. Here again I get jumpy values, it does not stay constant at all jumping from mOhm->Ohm->kOhm

I think Im most likely going to give this unit into repair to a technician, seems like I'm missing the skills to troubleshoot the cz...

[IanB]

This might seem like a daft question, but you have taken the batteries out, right?

[momo]

Sure thing! I havent run it on batteries in general, bought some in order to test if it may still run on those but it does not, so I took them out again

[IanB]

Hmm, this is very hard to diagnose without being "hands on". The simplest explanation is your probes aren't making good contact, but other than that it might be because there are other voltages present in the circuit. Or something intermittent- dry joint, cracked trace, etc. Bottom line is, blue to red should be a straightforward 0 ohms (or near enough) short circuit.

[momo]

A Friend found the problem and it were two bad transistors! Now the cz will Power on again

but new problems emerged as the line Output Is rather quite now  (before all the issues it seemed almost too loud) and a static hiss - that seem to be affected by the Psu - with no real sound-Output on the headphone jack. 

any clues in any direction? 

[momo]

At this point, it feels like I should've started a thread regarding my cz issues, instead of spamming this thread here ^^

I was able to figure out that the relai in there might be an issue regarding the output. Thus, according to another thread I tapped it at the 1k and 100k resistor to come along with the same weak output signal.
Thus I went a step further and checked OPAMP 4558DD's in and outputs as this one provides both jacks with sound. The input of those is louder compared to their outputs, does this point me towards replacing the OA as it seems defective? 
 

[IanB]

Might be worth asking your friend again

 

First thing to check is that the op amp actually has power. It's possible the amp board has no power.

[Brad Saucier]

13 minutes ago, momo said:

At this point, it feels like I should've started a thread regarding my cz issues, instead of spamming this thread here ^^

 

Done.  I had to give it a title, but you can edit your first post to change it.  

[momo]

16 hours ago, IanB said:

Might be worth asking your friend again

 

First thing to check is that the op amp actually has power. It's possible the amp board has no power.

I think you are right, just checked and it seems there are only 0.85V on the input of the JRC4558D, following back the schematic, this might be due to t11 emitter. I checked that transistor in diode mode! Whereas one leg seemed fine the other read none, I guess this points me to another defective transistor in there?! Will consult the friend later today!

[momo]

Mhh, I'm still scratching my head - friend only gave me a short heads up that in his opinion the other transistors seemed fine. 
Following the instructions regarding +VBR adjustment on here: https://erichizdepski.wordpress.com/2020/07/18/casio-cz-1000-repair/?fbclid=IwAR3FNM15Vefreu2Rqln0iPo9PfgbT-dMov8y0s-ZbyHGbI7w2yOplK77Gg0
I tried to get t11 Emitter to 4.3V but to no avail, I can easily measure and track the voltages on t8 which is right before t11. Setting t8 to 4.3V makes t11 1.2V... It seems like I cannot go past 2.3V for t11.
Furthermore I have problems to measure the variable resistance, it is bouncy and instead of going to max. 500k as proclaimed on the PCB it goes up to 1200k, thus maybe a broken trim pot?

[IanB]

Hmm, if you've already got dead transistors T11 may be suspect, if you can replace it no harm in doing so. T8 and 11 are acting as a darlington pair so this implies to me T11 is faulty.

 

Variable resistors shouldn't be "bouncy" at all but the JFET may be causing that, you'd need to desolder it and test it out of circuit to test it properly.