Strange behaviour starting up

[dzenat]

Hi there,

I managed to update the firmware to 2.10. nice.
Then I made a mistakte by unpluging the usb cable out and now i can't even start up the preenfm.

The blue lights blink but nothing happens on screen ....it's all black.

Is there a reset some where to reset the system? or should I reload the firmware? I made a copy of firmware 2.08 before upgrading...

Any help?

[dzenat]

Seems like after many tries, i finally manage to start up fine. But when playing with it, the screen display strange letterings....I don't understand what actually went wrong there...  to the developer, any ideas?

[Xavier]

Sorry for the delay I'm on vacation far from home until august 5th.

That cannot be a firmware problem.

That's likely a bad solder joint or a missing 'led' resistor.

[Soop]

Was there a solution or explanation for this?

I have just built a unit from a VanDaal kit and when starting up, briefly get squares then PreenFM2/Xavier credits/2.10, etc then it is blank. If I press buttons, I get nonsense/reverse words.

Is there a likely cause? I have been checking my solder joints and I can't spot anything. Hopefully I haven't missed anything obvious!

Any ideas or help would be greatly appreciated....

[Soop]

Pics just in case I missed something obvious...
 


Hopefully my out-of-practice soldering is adequate! I did mess up with one of the 100nf caps (pic 1, to right) and had to attach above the holes but am hoping it's ok...

[Soop]

I have been checking points with a multimeter from a picture in a previous post (thanks Xavier - really helpful!). Am powering with USB via a MacBookPro to test.

Everything seems ok except the two points coming down from the OLED header connection (next to the 100nf cap, close to the 6N137), which show only 3.47v - I believe it should be 4.2v rather than 5v with the 22ohm resistor?

I also noticed that the display changed to blocks while I was testing. I even tantalisingly got the correct home screen for a brief moment before it disappeared - so close! Really looking forward to getting this excellent synth going so fingers crossed for tracking down a solution and I will share as it might help others who come across this issue.

By the way, this forum is a really great resource - many thanks!

[Xavier]

The 3.47v can be because the blue oled draw more currant than the yellow.
You can try a smaller OLED resistor or simply shortcut it to check if that solve your problem.

You should also resolder ALL your junctions related to the OLED. There seems to be too much solder.
https://learn.adafruit.com/adafruit-guide-excellent-soldering/common-problems

Try to resolder the 16 on the PCB, the 16 on the display and the 20 upper points of the preenF405.
Put your hot iron on each point and wait for the small ball to melt and go down.

Xavier

[Soop]

Thanks so much for your advice, Xavier! I really appreciate you replying so quickly.

Apologies that my very basis skills caused a problem. Actually I wondered whether the connections were not good so added more solder - obviously the wrong way to go and not very helpful! I will try these ideas. Thanks again.

[Soop]

I resoldered my blobby joints but interestingly disconnecting the OLED resistor has got it working! Phew!
Some pages slightly dimmed on the screen. I will try a lower value resistor or a jumper when I have time later. Then audio...
Thanks again!

[Xavier]

...I will try a lower value resistor or a jumper when I have time later. Then audio...

The "Led"  is the Display power connection.
So it must not be empty or it won't work correctly.

The 22ohm allow the "Yellow OLED hiss mod". Not sure it's still usefull with the latest BLUE OLED.

You can just solder a resistor leg instead at the "Led" points.

[Soop]

Ah, that makes sense - many thanks Xavier. I inserted a jumper instead of the 22ohm resistor and now I have audio and USB midi working.

What a great sounding synth that you made! So full of character and a powerful sound.

Thanks so much for your help.