XW-P1 not responding to MIDI control!!

[perldude]

"Its dead Jim!"

 

Well, I had just had got the step sequencer programmed and got to start and stop with commands from my FCB1010. It took a lot of reading of the manuals and watched some of the Youtube videos. Then 1 small tweak to one of the FCB preset codes and BAMM!! the XW won't to ANY MIDI performance commands.  After some fiddling around I got it back but yesterday it failed again

 

Am I SOL, or are there options I  can explore?

 

One of the settings that got me going with the MIDI start/stop with the step sequencer was setting the MIDI sync mode to slave and having the FCB start the MIDI clock with the BPM controlling the tempo.  I only have one patch that uses this, so I set the MIDI Sync mode to off and  tried other patches and still no go. I think I need someone to look at this keyboard, because I already thought the MIDI out is electrically broken now I wonder if the MIDI UART is hosed.

[perldude]

I did a backup using the Data Editor, then did a factory reset.  Set the midi basic channel, made sure MIDI IN was on,  sent some midi commands which would have probably engaged untitled user presets, but no change in the display. Restored from today's backup (8/8/22) and still no go.  I even tried to restore from 7/25/22 and still no go.  

[Brad Saucier]

It's certainly possible the MIDI port is damaged.  If you've ruled out everything, sounds like you have, that's the only thing left.  Try putting your finger on the port and see if you notice any unusual free play.  You might even try that while running MIDI through it, see if it happens to start working with some pressure on it.  

[perldude]

Last night I broke out the scope, opened the XW lid and examined the small midi board with the midi connectors.  I found that ground connections internal to the synth are isolated from my scope earth connection, so I ran the XW-P1 on batteries (a nice option for this synth!).  This is very important when working on electronics like this because in that way I can float the synth to the ground potential of the scope without the danger of high circulating ground currents. I used the FCB1010 to generate the MIDI clock so I had a repeating pulse on the midi input.  From the midi input connector they have common mode chokes on the input midi current loop, and I was able to measure the forward bias, about a volt across the emitter diode, but at the opto collector no signal, just partially pulled down to about 3.4V from 5V. It's hard to say, as I would have expected opto damage to have occurred at the opto input (emitter diode).  The opto output at the collector is pulled up to 5V thru 220 ohms, so when the diode is forward biased, I would have expected some sort of inverted pulse at the collector, so either the opto is hosed or there is pretty hard short down stream at the UART which could be broken. The opto replacement is low hanging fruit.  It's hard to read the part# of the installed component, so I have to find a find a SMD 5 pin opto that meets the MIDI criteria (20ma Id max, CTR 20% or higher, reasonable speed). 

[Jokeyman123]

Stray static through what looks like a fairly frail optoisolator IC could have blown it although since you are getting any readings at all from emitter to collector, maybe not.  Assuming this is a simple LED opto, if the opto LED blew inside I would think you'd get no values at all at the output so unfortunately something else may be going on.  I would try to get an entire replacement board if you can't get the chip. If your suspected ground short suspicion is correct, how are the connected caps? As always, check for hairline fractures in your din socket solder connections-I use a jeweler's loupe, which has helped me find solder cracks I had no idea were apparent even with a good magnifying lens.

[perldude]

Hey Jokeyman123,

Thank you for the comments.  I have attached a diagram that I derived from examining the board and the measurements I made.  You can see that following the MIDI input connector is a common mode choke that attempts to reject noise (and hopefully transients like static discharge) common to the traces connected to pins 4 and 5. After that, the same lines connect to a reverse voltage protection diode because the opto emitter diode reverse voltage max is -5V.  The combination of the common mode choke and protection diode is cheap protection, but works in most cases.  However, because MIDI thru was not working for me, I kept having to connect the midi to my MUTO every time I wanted to change/program my FCB settings, which could have beaten up the input time and time again.  I also realized that there is not a pull up resistor on the opto output and pin 6 of the opto is tied to 5V, so the output is most probably a low impedance (logic) driver and not a transistor collector.  So today I bought some Onsemi FODM8071 optos.  They have the same footprint and specs and are faster.  Hopefully they arrive soon.  In the attached image I also layout why the MIDI loop current is 5.45ma on average.  I know....I am a complete geek.

[IanB]

My instinct is that this isn't the opto. Let's see 

[perldude]

Yes, equal chances its not.  My MIDI out has never worked properly, so I am inclined to suspect the UART.  But the opto is low hanging fruit and shares symptoms.  If it is something else, I would need to get it serviced.  How do I make that happen?  Who do I contact at Casio?

[perldude]

Still waiting for my digikey order of new opto-couplers, but I still wanted to remove the ambiguity if the opto is bad or not.  Not knowing exactly what the opto part number really is, makes me unsure if its a open collector output or a digital driver output. My guess is the latter because there is no pull up resistor on the midi board and it could be at the other end of the cable connecting to the UART.  I don't think so because that would be a bad signal integrity design. So tonight, just in case it is an open collector output I de-soldered the opto output pin, carefully lifting it off its pad.  I soldered a 510ohm resistor between the output pin and the 5V pin. Regardless if its a digital output or open collector, it is disconnected from the load and if it is still working I should see the pulse at the output.  Drum roll......    nothing. The part is dead. That is good news, but it doesn't mean I don't have two problems, but my chances are better that I can be up and running when I install  the new opto when they arrive (I bought 3 in case I screw up).

[Jokeyman123]

Easy enough to blow an opto internal diode. UARTs are usually pretty robust, but then I don't know what Casio is using for their UART.

 

The main Dover, NJ location had a repair technician last I needed one, but that was before the pandemic-and you would have to ship the entire XW to Dover, NJ. I had a CDP230 which i could not repair and they sent me a refurbished replacement as the tech did not have replacement parts needed to repair my original. Its worth contacting them I would think anyway if you cannot suss this one out. Chances of finding a replacement for the midi din port board is slim on the used market.

 

I am surprised digikey sold you only three parts-usually these large vendors only accept large orders-good news for anyone (like moi!) who does their own repair work or even pro techs.

 

A possibly stupid question- don't recall-are the midi din circuits completely separate electronically from the USB midi connections in the Casio? And are both your din and usb midi out connections dead? I have to bone up, but I was under the impression a usb midi data connection does not even use the UART, so your usb midi connection should (theoretically) still work. I could be wrong still have alot to learn but my midi host boxes have uarts built in so I am guessing this is the missing usb midi IC in usb midi only controllers/computers etc.IanB do you know?

 

Troubleshooting-eliminate everything that works, and trace down to what doesn't. You're not geeky, just thorough. Can you help me design and build a new PSU for the Alesis Fusion, its failing weakness with no possible replacement parts anywhere?😋 I'm kidding (well not entirely). At that user group, we have been struggling to solve that puzzle but that is another story!!!!

[perldude]

Jokeyman123,  Thanks for the repair info, I didn't realize they had a facility in Dover, it less that 50 minutes from my home, I could drop it off.

I got my electrical engineering degree in 1987, but have been interested in electronics since I heard my 1st ELP recording when I was a kid.  After high school I had a hard choice, rock star or EE.  I figured I liked eating, so I chose engineering.    It's hard to say not knowing how integrated the circuits are in the Casio.  But yes the USB midi wouldn't use the UART, it would use a dedicated USB controller. They could be using a system on chip which integrates the UART and USB functions.  UARTs are frequently incorporated into SOCs.  I had better luck seeing the midi data out of the USB port but it was a very much filtered version of what was going in.  MIDI is essentially RS-232 with a protocol layer.

That Alesis Fusion looks like a pretty cool synth!  PSU = Power Supply Unit?  What are the specs?  What is the connector?  Perhaps send me a link to that group discussion.

[perldude]

Parts arrived in the mail this morning.  The new opto-coupler did the trick.  I then did continuity checks on the MIDI output connector along the PCB traces and found the pin 4 connection pad was cracked with no continuity to the common mode choke  pin.  Thank you Jokeyman123 for the suggestion in doing this check.  So I used braided wire (solder wick) to reinforce ALL the DIN pins 4,5 connections for both connectors.  I am up and running, and now that my MIDI thru works I don't need to repeatedly move the MIDI in connection to program my FCB1010.  One happy camper! 😁

[Jokeyman123]

Yessirree! 😀😀😀

 

Not all repair projects end successfully like this one did. Nice work. I live 45-50 minutes from Dover over the border in PA-how I found out about it.  Its next to one of my wife's doctor's offices, what a surprise that day was when I went to her doctor with her and whoa! Looky here! Its Casio's headquarters! and me with 5 Casios, I rarely fall into it like this!!!!

 

How I met Mike Martin who (this is top secret double probation info-only you and I will know🤣) I think...did some of his wonderful video tutorials there. I brought-coincidentally my new but malfunctioning XW there personally, and to my delight he was there and personally saw to it that my XW was repaired. I felt honored, still do. And still have my working XW. Thanks again Mike Martin.

 

Here is a link to the Fusion topic in question regarding the PSU's designed for the Fusions. Unfortunately, none of us can find a schematic for reproducing this which is switching mode supply with several voltage feeds, including a rather odd -16V power branch and we are seeking to keep these rather unique machines alive. Similar to efforts around the early Casios so many are working on restoring and playing. it is unbelievably powerful music making machine-with 4 separate synth architectures. But does not replace my Casios, serves as an admirable partner in the creative process.

 

https://www.alesismusic.com/viewtopic.php?f=16&t=7887

 

POI-I was late to the game with these supposedly "obsolete" Fusions which I recently restored and which have almost completely  taken over my creative work aside from my Casios. Decided to go this way due to the tremendous technical support from the outstanding moderators there-very much as here-and after much research learning the history of these, had nothing but admiration for the developers-several of whom are recognized geniuses in sound development, especially to Steve Howell who developed Hollow Sun, sadly now deceased. But this is a Casio forum so i will leave it at that.