Part led, part button and part SD card problem

innsmouthrain

Hi!

I just gotta say, this is such a cool project! I'm a musician and programmer and this is one of my first ventures into electronics, but it's fun and I'm gonna be such a proud owner of an LXR when I'm done.

I hope someone can help me out of this, I'll be so sad if I can't finish this! But I have a good store nearby and if someone understands what's wrong I hope it'll be fine.

On bootup I get the green voice LED instantly and I get informed about bootloader being of version .23. Then the display tells me "SD card not detected!"; I have an SD card inserted. It's formated to DOS FAT32 and unpartitioned with all the files from http://sonic-potions.com/public/SdCardImage.zip unzipped into it. The encoder and the leftmost three pots work fine. 

First 7 LEDs in the sequencer light up if I hit their buttons (first one seems to be a bit broken, so I'll try to get a replacement for that one - it doesn't click and is overly sensitive). But the start button does nothing.

I had a small accident with a resistor network. Just after soldering a 10k resistor network I realized it was in the 220k spot and it broke when I removed it. I replaced it with this: https://www.elfa.se/elfa3~en_gb/elfa/init.do?item=60-324-78&toc=19980 - It should be fine, right?

I've also noticed that I don't see a leg sticking out on the topside where the mainboard leg labeled "NRS(?)" (6th leg, right under MIDI Out leg). If this is the problem, how do I fix it? But this can't cause both the SD card and the LED problems, right?

Ideas?

Best regards,

Love von Melen

julian

regarding the SD card.
check the soldering at the IC HC4050.
SD card not detected means it can't find a SD card at all. So it has nothing to do with how the card is formatted.

the replacement network seems to be the right one.

I don't completely understand where the 'leg' is missing. On the small mainboard or the big frontpanel?

Are other buttons working or only the first sequencer buttons? there might still be a bad solder joint somewhere in the hc165 chain. the sequencer buttons are the first in the chain. if there is a bad connection all the following buttons won't work.

You can find some instructions where to measure in the troubleshooting section in the wiki http://wiki.sonic-potions.com/index.php/LXR_Troubleshooting

innsmouthrain

The leg would be sticking out on the top of the frontpanel, yes. And it's just not there. I was very surprised!

!! I had the 4050 on the wrong spot. I must've messed it up while double checking all the ICs before.

Now all buttons seem to work but they don't give entirely predictable output. Sometimes every LED flashes and I can't seem to use the sequencer buttons right now. And the display gave me

"not detected!
SD CARD"

instead. I'm looking at the wiki and I want to test for continuity but it's hard to figure out which ones are pin 27, 28 and 29 of the AVR?

julian

Ok we are getting there in small steps.

This is the way you have to count the pins

julian

how did you mix up the ICs? wrong position? inserted backwards?
did anything get hot or smell funky?

julian

the NRST pin is used in the bootloader to reset the mainboard.
for now it is not important.
first we should get the rest to work, then we can figure out whats wrong with the missing leg/pin.

innsmouthrain

I put the 4050 where there was supposed to be a 595 and vice versa. Okay, gotcha on the NRST pin.

I also apparently completely forgot the put the mainboard back on the last attempt there, so with it on i actually get sounds.

All LEDs seem to be working. Some buttons do nothing and some buttons seem to interfere with others. For instance, I can't unselect the last sequencer button, but clicking it is like clicking both buttons before it.

Now I feel kinda scared. Is my soldering technique so bad that there's just that much interference between the buttons? I can't see anything wrong, looking at the solder, but could it be the PCB got overheated or something?

I'm gonna check for continuity now with the help of that very helpful picture.

julian

there is not much that could be damaged by too much heat.
As long as there are no traces scratched. but that could be fixed with a piece of wire too.

I think this is a short somewhere or a cold solder joint on the 165 ICs.

Hehe, I forget to re-attach the mainboard from time to time, too.
You feel always stupid after wondering for 5 minutes why nothing works anymore

regarding the last sequencer buttons - check the connection between the highlighted traces on the following picture:

these go to step 14,15 and 16 and should have no continuity between them.

julian

are all your resistor networks inserted the right way?

innsmouthrain

With the help of the wiki instructions I located a bad joint on a 165 and now it's a little bit more stable. But the rest of the continuity tests worked out fine. Including between pin 11 on that 165 to the first pin on the 10k resistor network. All the resistor networks seem to be correctly aligned too.

julian

so what are the remaining problems with the buttons?
Is the last sequencer button still not working porpperly?
then please measure also the continuity between all 3 of those pins of the 165 (pin 11,12,13)
they should have no contact to each other.

innsmouthrain

The remaining problem is a bit hard to define. The last sequencer button is fine but 8 and 10 are not anymore. Or maybe it's just their LEDs.

A lot of buttons don't work. I can't seem to switch between voice and performance, while the 'voice 1' button seems to do a bit of everything when I press it. I can't hit the 'Start' button on bootup but after pressing around a bit it seems to work.

julian

ok...
could you systematically check these button groups

• U2: Seq. buttons 1-8
  
• U5: Seq. buttons 9-16
  
• U6: Select buttons 1-8
  
• U12: Voice buttons 1-7 and Copy button
• U10: Start, Rec, Shift, Voice, Perf., Step, Load/Save
  

and report the first group of buttons where one is not working.
this helps to pinpoint the location of the remaining issue.

the thin is that the 165 ICs are connected in a chain. so if there is a loose contact or missing connection or a short somewhere, the following buttons in the chain won't work propperly.

here is the connection for button 8

and here for button 10


are the ICs all seated propperly in their sockets? Pushed all the way down?

innsmouthrain

Yeeesss!! All the buttons works! And a beautiful beat came out of it this time! (Before all sounds were distorted, probably because of settings being altered constantly by buggy button behaviour)

It seems I had shorted the Voice 1 button to its' LED. Such silliness!

Thank you so much for your great, great help! Even for newbies like me, you take the time to get our LXRs working!

The pots are acting slightly strangely, as is the save/load button. The pots are interfering a bit with eachother. This is fine when it's just the 'fine' value being +/- 1 cent, but when I'm in settings I suddenly save a kit instead of loading it, etc. I probably did some terrible soldering to the poor pots. 

But while I'm looking into that. What can be done about the missing leg?

I would remove it and see if I can find a bent leg to straighten out, but there are 26 soldered joints stopping me. Is there an alternative?

innsmouthrain

BTW. Just for future reference. I also put extra solder or heat on a lot of joints after getting tipped off to the first bad joint on a 165. So some buttons, leds or ICs have possibly been fixed by that. Button 8 and 10 as well as the 'user' button all seem to have some problems with their LEDs, so they might have worked properly before as well.

julian

first I would test that the pins around the missing leg have no contact to each other.
If it is bend under the connector it could short out its neighbour pins.

can you measure if the missing leg has contact to the mainboard?
otherwise I'd say solder a cable from the pad on top to the mainboard nrst pin (where normally the leg from the connector would make the contact)

This solution will not be pretty, but removing the whole connector to look for a bend pin will be quite difficult without the propper tools and without damaging something

If the NRST pin has no contact, firmware updates won't work. Other than that it is not used.

innsmouthrain

I checked for continuity between the pins near the NRST and found none! I guess that should mean the bent pin isn't shorting anything. I pushed a clipped resistor leg in there and VOILA! Firmware updated!! So happy!

LED for seq button 10 and User button was wrong polarity. Seq button 8 however, I can't seem to light up. Tried switching the diodes around in case it was just broken. But the one working on button 10 didn't work on 8 and vice versa. What could cause this? 

innsmouthrain

LED 8 seems to work sometimes if Ifiddle around with my finger a bit on its solder? What does that mean?

Load/save button either "works" when pressed, but gets hit a thousand times a second, or lacks reaction completely.

I'm suspecting something with my soldering here, but it looks just like every other joint. Any ideas? 

julian

try re-heating the solder on led 8. sometimes a joint looks good but has no propper contact -> cold solder joint

load/save button could be a bad conenction to the 10k network.

When the button is pressed it is connected to 5V. When not pressed the input signal is 'floating'. That means it has no defined state which is bad. So to give it a defined state (off or GND) the 10k resitor to GND is used to 'pull it down'

innsmouthrain

LED 8 was indeed fixed by reheating. Surprisingly, for me at least, since I already desoldered and resoldered it twice without change! Good, anyway! Let's just assume my technique has gotten better since then.

load/save button still isn't working. I tried changing the button just to make sure it wasn't the culprit. It still behaves the same. Sometimes it's not responding, and when it is responding it's acting as if it is repeatedly pressed. The 10k networks look fine, and I've already reheated and resoldered them.

The button does seem to consistently react when I'm touching its side with my finger, but not when I'm clicking it. Does this give you any ideas?

innsmouthrain

And going back to the pots. The second, third and fourth pot actually change the first pots values very slightly, close to their max. The third and fourth move the second's and first's values and the fourth moves all first three values.

You said about the load/save button that it could be a bad connection to the 10k resistor network. Did you mean a bad solder joint somewhere on the 10k? Is it something I can check with a continuity test?

innsmouthrain

WHOO! I suck. I didn't see a cold solder on the 10k. But now it's fixed.

Is it something similar with the pots maybe?

innsmouthrain

Can't seem to fix the pots. It's a wonderful machine anyway, but if anyone has a clue, please tell me

Thanks for all the help Julian. I learned alot and gained a very cool drum machine

julian

what soldering iron are you using?
how much do the pots influence each other.
are we talking just a little change/jitter of 1 or 2 numbers or  is one button controlling the others over a wide range?

innsmouthrain

We're talking just 1 or 2 numbers back and forth across. I'm using a variable temp iron set to ~340 degree celsius (48W 50khz). I can crank it up to 450 degrees.

julian

hmmm temperature should be fine... i uses 303°C
Leaded or lead free solder?

about the pots... what power supply are you using?
Maybe it has not enough mA?

julian

there is not much that can go wrong on the pots besides sloppy soldering or shorted out pins.


left pin of the pots is gnd, right is +5V and the middle goes directly to the AVR ADCs.

innsmouthrain

Okay thanks that should be all the information I need then. It's too pretty and sounds too sweet to be taken apart right now, but when I can bring myself to it, I'll have a look at this thread and reheat and resolder all the important joints! )

julian

another thing you can check is the inductance L1 (power supply for the ADC) and the 100nF caps around the AVR