[SOLVED] OLED weird symbols and LXR not working anymore after trying to resolder oled

jeffclermont

So. I sent it to a trusted builder in the US and the problem, like every problems, was 3 missing solders on the main chip. I'll blame it on the sleepness nights of having a newborn. Thanks Ralph Wlodarczyk !

Hello everyone,

I finished building my LXR yesterday. I did all the tests, although my multimeter doesn't have a continuity test function, I check for voltage when the power supply is not connected and it didn't show a short, I guess, I also did a resistance test and it shows 1.59 k. The voltage test at steps 5 and 16 were good. (4.99v)The unit is powered by a 9v 600ma power supply. So, I powered the unit before installing the OLED and pretty much all the led lighted up, than the green voice led lighted up and I could press the start button and see the chasing lights.It's when I soldered the OLED that things started going wrong. After I soldered the OLED, I started the LXR and a bunch of weird characters showed up, I could still see sometimes parts of words, like «wav».I was able to see the chasing lights. I than decided to check the connection on the oled and resolder it by heating the pads a little. Now everything is black, no led lighting, nothing. I copied the latest firmware on my sd card (Kingston 4gb) and try booting up with the encoder pushed. Nothing.It's worth noting that I'm not super advanced in electronics. ;)I checked the orientation of all the resistors networks, the ICs. Everything seems fine. So... Is my OLED fried ? What can I do ?

cj55

Either there is still a bad solder joint, that means a bad connection of the display.
--> check the voltage between pin 1 and 2 of the OLED connector. Are you measuring 5V?

Or there is a short between the solder joints of the OLED connector.
--> measure the resistance between all adjacent pins of the display connector. The measured values should be well above some 100 Ohms. Do not power the LXR when measuring resistance!

Or there is a short under the OLED because the underside of the display touches the pins of the frontpanel board.
--> did you cut off the legs of all parts below the display as short as possible? Or better did you use some isolation like electrician tape under the display?

jeffclermont

Thanks, I'll look into that. I'm away for the week, when I'll get back I'll try these differents solutions. Thank you !

jeffclermont

So, hi, I'm back.

I tested the voltage between pin 1 and 2 and I get 4.99 V.

I tested the resistance between all adjacents pins of the display connector and I get 1 on my multimeter, adjusted on 200 ohms (I also 1 when the multimeter probes are not touching and I do nothing). So does that mean it's a short ?

For underneath the display, I tried to cut the parts below as short as possible. I don't think there's a short, but I'll try to slide a piece of electrician tape under it, as it's really hard to unsolder and remove. 

Speaking of desoldering, do you have any tricks to do it on the OLED ? I have a solder pump and I managed to remove a lot of it, but it's still really hard to remove the display...

Your help is appreciated. I'm sure I'm near a solution ! 

cj55

>>I than decided to check the connection on the oled and resolder it by heating the pads a little. Now everything is black, no led lighting, nothing.

Did you maybe resoldered it while the LXR was powered?
And what do you mean with everything is black? No LEDs lighting on the LXR at all?
The symptoms (before all went dark) could also caused by a too weak power supply. Often power supplies deliver much less mA then they are specified for. Can you try another with more mA?

>>I tested the voltage between pin 1 and 2 and I get 4.99 V.

That's good!

>>I tested the resistance between all adjacents pins of the display connector and I get 1 on my multimeter, adjusted on 200 ohms (I also 1 when the multimeter probes are not touching and I do nothing). So does that mean it's a short ?

That's good, no short!

>>Speaking of desoldering, do you have any tricks to do it on the OLED ? I have a solder pump and I managed to remove a lot of it, but it's still really hard to remove the display...

Desoldering the display is not easy. The best way is to cut the pins (and the black plastic) between the OLED and the frontpanel board). THEN you can desolder every single pin, one after the other.

jeffclermont

I don't think I resoldered it while having power on it. It was late in the evening...

Everything is black meaning no LEDs lighting at all on the LXR. Before I installed the OLED, I could press on the start button and see the chasing lights. Now, nothing at all. 

I'm waiting for a new power supply, a 9v 1a. Hopefully it will solve everything. Fingers crossed.

I must have done something wrong to the circuit since I can't see any LED lighting. That's why I want to remove the OLED and test it out.

Is there a way I could verify if anything is fried ? I read somewhere on the forum that I could reset the AVR ? Maybe that's part of the problem ? How would I do that ?

jeffclermont

So I received my power supply.

I managed to desolder the OLED display. Then I tried the new power supply (9v 1a). Nothing working. No led lighting. I'm close to being desperate. :-/

So now, how can I troubleshoot ? What's next ?

Maybe it's the AVR not booting correctly ? How can I reset it ? 

julian

so just to recap:

- without OLED the LXR worked (LEDs light up, chaselight etc)
- soldered OLED -> nothing wokrs anymore - no LEDs etc
- you removed the OLED
- new powersupply
- still nothing, no LEDs etc...

so lets see:
- Do you still measure 5v (or 4.99) at the AVR ISP header next to the AVR? it'#s labeled with +5V and GND.
- is the AVR seated completely in its socket?
- after powering up the synth. is pin 5 of the AVR high (+5V). it should start low and turn to high after a second of so.

jeffclermont

Hi !

Your recap is correct. 

I had a couple of weird behaviors. I replugged the new power supply and suddenly the Rec led (the red one) lighted up. No SD cards inside. For a while, I wasn't able to reproduce it. Then, I played with the power supply plug and boom, all the led lighted up, apart voice 4 and 5. But no chasing light when I press on start. The device seems unresponsive. I can't reproduce it though.

1. I still measure 4.98 V on the AVR ISP between +5V and GND.
2. the avr is seated in is socket 

3. To read on pin #5, do I use the GND on the ISP header (the black probe on GND and the red one on the pin ?). If so, I read only 0,05 V, sometimes even less, 0.03 V. 

jeffclermont

Also, I'm trying with 3 different power supplies. 

1. One is 9V 1a;

2. One is 9V 650ma;

3. One is a universal adaptor (one with multiple voltage configuration, set at 9V) with supposedly 1000 ma.

jeffclermont

I'm running out of options. Is there any way I could send it to be fixed by a trusted builder ? I'm the father of a newborn and the time allowed to work on the device is pretty limited. I would gladly pay for shipping and fixing.