Re: Reading Serial Midi data with an oscilloscope
That is true. Luckily I bought a few extra. When I feel like it I'll get around to looking around. I got another console that works, so its not immediate that I try to fix this one....
zombie.guitarist
Member
Last Activity: 12-20-2023, 10:17 PM
Joined: 06-25-2023
Location: Long Island, NY
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Re: Reading Serial Midi data with an oscilloscope
After a couple of weeks, I finally got a 63B50P chip. Put it in and still nothing haha. So it isn't the chip, but to be fair, I just tested output. I didn't read the Tx pin with the scope, but none of the other ports worked so I don't think it could be anything else after that. So it may be something feeding into
the IC12, I just can't think what else....Leave a comment:
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Re: Synthaxe Midi Controller footswitch
Hah, thats a good way to remember it, and you were right! The issue is, both the diodes tested working when I removed them haha. So now I'm really stuck because without a schematic, I can't really go much further, aside from just changing the other 4 capacitors and hoping for the best!
I suppose it's time to take this a little further with someone with more expertise and knowledge to diagnose it....Leave a comment:
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Re: Synthaxe Midi Controller footswitch
I know thats a 100% safe way to test, but wasn't sure if it was necessary if you can get the same reading while in circuit. Should the rule be, always test components out of circuit? I know you have to with caps....Leave a comment:
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Re: Synthaxe Midi Controller footswitch
Update: I removed all the Resistor array/networks and they all tested good. But I also tested the voltage drop on the 3 diodes in circuit. They all tested correctly forward, but diode 1 and 2 give me a reading reverse, so that may be the issue.
The problem is, since I don't have the proper schematic, I can't quite tell what part number diode they are. I'll have to post a picture of it in another part of this forum.Leave a comment:
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Re: Synthaxe Midi Controller footswitch
Ok great, thanks for the tip! Just to recap, I replaced 3 chips that are connected to the issue (6402, 7432 and HEF4013) as well as all the 104 caps (which was 9 of the 13 caps on the board). Theres not much left to poke around haha....Leave a comment:
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Re: Synthaxe Midi Controller footswitch
Does this happen with a bussed resistor network?
The resistor array that I think is attached to that trace is a 770-91-47. I
haven't went back and checked what all those resistor networks are attached to.
770 is the part, 9 is the # of pins, 1 is the schematic (Bussed) and 47 means
47k. Pin 1 gets the Vcc and the other 8 pins are 47k, so I'm unsure if I can
test that in circuit or remove it? Heres the data sheet:
[url]https://cdn.badcaps-static.com/pdfs/3b9b97320c6290dc32c2b3d3658b4995.pdf[/url]...Leave a comment:
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Re: Synthaxe Midi Controller footswitch
Ok a bit of an update. I got my 104 caps in and first replaced the one I thought was faulty. I still got the same problem of the "+" light staying on, but now instead of staying on until I shut the unit off, it gets cleared when I press the "-" button.
I thought I'd be safe and replace a few more caps that were the same 104s. The only ones I didn't touch that I knew worked was the one for the voltage regulator, and the one for the crystal osc, which both work fine. So now I'm not sure where to go. Either the...Leave a comment:
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Re: Reading Serial Midi data with an oscilloscope
Doesn't sound like a bad idea if you have a hot air gun. Anyway, I'm gonna order a 63B50P from China since no one else has em. Hope that does the trick....Leave a comment:
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Re: Reading Serial Midi data with an oscilloscope
Update. Removed the 4016 (IC32), and still no data from IC12 pin 6.
I actually took the chip out easily and lifted a part of the trace, but I put in a socket, and checked it for continuity and it was still connected. Its like these pcb traces are more fragile than the NES PCBs.Leave a comment:
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Re: Reading Serial Midi data with an oscilloscope
I used to have a good desoldering gun when I was making NES games, and desoldering chips was a breeze! For some reason, with this PCB, it seems much more fragile. I already had lifted a trace even though I was STUPIDLY careful on IC 14, but it was an easy fix because of that Data bus, so I just jumped it to another pin. I ended up getting another desoldering gun/pump that seems to work pretty well. I'm just trying to be as careful as I can. I did just buy another console and step pedal as a backup, but I don't know...Leave a comment:
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Re: Reading Serial Midi data with an oscilloscope
Thanks. Will check that at some point. One quick question though. Would it be a little easier or less destructive to just replace the IC32 4016 first?...Leave a comment:
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Re: Reading Serial Midi data with an oscilloscope
Success! You were right about not only probing the input of the buffers, but also using the 10x. I tested the working MIDI, and got Midi data from pin 10 and 12 of the 74C906.
Now, moving on to the actual problem, the console. IC 12, 63B50.
The results are, I got signals from everything (well except the RxD pin cuz nothing was connected to it). But I got working signals for the TCK/RCK/E/RW/CS (when midi data was present)/IRQ (also when midi data was present) and all the data lines. The ONLY pin, I could...Leave a comment:
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Re: Reading Serial Midi data with an oscilloscope
Ah ok, did not know that. I have one of those handheld scopes, the FNIRSI-1C15. Last night when I was probing, I can't remember exactly what I was probing, but it was either Pin 11/13 on the 74C906, or Pin 4 of the 220 Resistor array. Ill take another look....Leave a comment:
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Re: Reading Serial Midi data with an oscilloscope
I wanted to chime in with this. To double check, I traced on the footcontroller, the signal path for the working midi, so I could probe it easier and test what correct data would look like on the scope. I didn't get anything. 5V was tied to the correct pin, but when I tried the Tx data pin for the midi, I didn't get anything. Tried multiple voltages and even the fastest/slowest second readings I could and didn't see anything. Again, I KNOW that midi port works. So, there must be something that reads that kind of midi serial data...Leave a comment:
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Re: Reading Serial Midi data with an oscilloscope
Ok I can do that. I can't remember if I tested pin 11, as its bussed to IC 10 and IC 11 as well and figured if those 2 work, it should be an issue with IC 12.
FWIW, I tried testing the output on the midi port that worked on the footswitch. I put the scope inside the MIDI Din, and was able to read 5V on the one pin, but nothing on the other, but I knew that worked and was output MIDI data from the controller. So I thought perhaps I just couldn't read the data with what I have.
First, I...Leave a comment:
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Re: Reading Serial Midi data with an oscilloscope
Ill try that again. I tried scoping the working midi port as a reference to see what a working signal would look like and wasn't getting anything. I think i was at 2V. I tried all the different time divisions as well and couldn't see any data, even trying to trigger it. But more importantly, what you're saying is you don't really need any other equipment since I'm not trying to decode it?...Leave a comment:
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Re: Reading Serial Midi data with an oscilloscope
Just an simple oscilloscope and a DMM. I tried looking for videos about reading midi data online, but the only thing I could find was someone using a working DIN Midi cable, into an Arduino. Im unsure how to read that kind of serial data directly from the Tx line itself....Leave a comment:
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Reading Serial Midi data with an oscilloscope
Hey all, I have one last thing I'm looking to fix with my Synthaxe. This time, the schematics I have are actually the same as the PCBs I have.
The Synthaxe, works as its a guitar midi controller hooked up to a floor pedal. Thats the most basic way of using it, and it has a midi output. You also can connect a console to it, that stores your tunings and other things. The console has 8 midi outs, as well as a midi in and midi thru.
When I first got the unit, I thought I was using it wrong, but it turns out its just broken. The 8 midi ports on the console don't output... -
Re: Synthaxe Midi Controller footswitch
It wasn't reading anything, so I suppose open. I removed 3 to test. The problem is, the legs were too short to be inserted into the slots on the DMM, but after wiggling, I was able to read 2 of them at the right values. The one that didn't work, no matter how hard I tried wouldn't read at all. Since all the legs were about the same size, I concluded that it was reaching the pads but nothing was being read. I mean for $3 its a simple fix. The cap that was bad was connected to IC1's pin 11 thru a resistor network.
...Leave a comment:
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