resisitor network orientation?

[benjaminr]

Hello!
My name is Ben, very excited about this synth! I've built a few little synths and things before (atmega and teensy based mostly), but this is my first ever PCB build!

My question is: which holes on the PCB correspond to the common grounds for the resistor networks?

I'm just troubleshooting/diagnosing and am not confident in my initial assumption that the square holes are ground (I used 16 10k resistors and just made my own networks, so it's not as simple as lining up the arrows). From looking at different sources it seems like sometimes these networks' common terminal is on pin 1 and sometimes on pin 9?) My local shop doesn't stock 9 pin networks so I bought a couple 11 pins today and trimmed off two of the leads, so I'll probably plop though in instead of messing around with all the extra solder points.
 
Not sure if this is where my issue is (blank screen, 3 solid leds), but I want to be sure I've got it right before moving forward with diagnostics. Lol I'll likely have another question or two if I can't get it figured out.

Thanks so much Xavier for your work on this project, it sounds like a terrific synth and I'm very excited to get to playing with it!

(edits: spelling)

[Xavier]

Hi Ben,

16 10k resistors to replace the network, nice   

Do you have the building doc ?
http://ixox.fr/preenfm2/build-it/thebuild/
Search for "network" and you'll see the network resitor picture in place.

But i don't think a problem with the network can lead to a blank screen.
Don't hesitate with your questions, that's what this forum is for.

Xavier

[benjaminr]

Hey, thanks for the reply!
Yeah, I followed the build doc for the whole assembly, but for the part with the resistor networks it just shows the networks being placed according to the dot on pin 1. I just wanted to confirm that the square through hole is indeed the ground pin/common terminal for the network (I'm like 90% sure it is, but on the website for the resistor networks I bought yesterday it says the last pin is the ground so I'm just not confident.
I'm at work now so sorry if I'm slow to respond!

[Xavier]

I just wanted to confirm that the square through hole is indeed the ground pin/common terminal for the network

OK i see. Yes it is !

You can easily check with a multimetre how your network is built.
10 K ohm between the common pin and any other one.
20 K ohm between any of other pins.

[benjaminr]

Awesome! Yeah I had the networks themselves figured out was just tripping about the orientation in the PCB. Looks like I had then right in the first place lol. (Square solder pad always means ground, right?) Thanks so much for the replies! Gonna reflow all my connections tonight and check my component values and then I'll probably have more questions!
 I'm in Vancouver, Canada so it's currently 630 am for me

[benjaminr]

Ok! Getting somewhere I think!
Installed the networks again, reflowed everything, cleaned up the flux ...there was a lot :O
And then I started checking the voltages/grounds as Xavier described in this thread ( http://ixox.fr/forum/index.php?topic=63470.0 ). Everything's good... EXCEPT the 2.5 V points. I'm getting no reading at all from any of them!
Any ideas?

...this is fun

[benjaminr]

Probably worth mentioning that I've modified things slightly... I'm mounting the Preen on a panel which has a 3 way selector switch (ON-OFF-ON) instead of using the power jumpers...

So the usb jumper (J2) runs from the usb into one side of the 3 way switch, and an external 5v source (for now a usb cable soldered onto dupont connectors, later a 16 pin eurorack style socket) runs into the other side of the switch, then the output of the switch runs through a dupont connector back into the other side of J2 or into the 5v header on the south-west corner of the pcb. So the switch is USB/On-OFF-external 5v/On. I've tested it and it seems to work fine,

For diagnosing though, I'm just plugging that usb/dupont cable in the 5V/GND header, but I have tried with any combination of usb, switch, external etc, and all behaviour is the same. I installed the 7805 circuit since I already had the parts, but left the DC jack out, since I won't be using it.

As far as I can tell, this shouldn't affect anything, but just in case... :/

[benjaminr]

Oh, and I've not bothered with J1, since no power will be flowing through the 7805 anyways.

[benjaminr]

Yikes, sorry for the quadruple post, but I'm gonna take a break so here's a list of everything I've done:

reflowed each solder point, and tested fishy looking ones (blobs etc)
checked the values of all resistors with a multimeter
checked the values of the capacitors (and their orientation) visually
checked the board for solder points I may have shorted
checked the ICs, whether they are the right ones and whether they are correctly inserted
swapped the TLV2472CP with an MCP6002 (then back after no change)
cleaned all stray flux off the board
attempted to boot into various modes using button presses/holds at startup (screen is completely blank no matter what, booting with button 1 does not make the device show up as USB storage on my computer)
attempted to boot into DFU mode using jumper 3
triple checked jumper 3 was open with multimeter
checked connection of each pin of lcd screen to pcb using multimeter
checked that buttons were open/functioning properly when unpressed and pressed
booted without the PreenF405 not inserted into the 40 pin DIP socket--screen is still blank, but the leds do not light up.
confirmed that 4th, unlit, led was not dead by applying 5v via a 220ohm resistor directly to the legs (lights up fine)
checked continuity of each pin of the PreenF405 with the socket/pcb (multimeter from top of F405 to solder at bottom of PCB)

Sorry for such a long post, I'm thinking with the timezones seems like it'd be a bit slow to say "yes I tried that" once a day lol.

From looking at other threads I'm thinking I need to maybe try flashing the bootloader and firmware?
What I think I need for sure is to go to bed haha
Thanks for all the help so far, enjoy your weekend and don't rush to respond, I'm excited for the synth, but it's not gonna kill me to be a bit more patient.

[Xavier]

That's a lot of information.
The 2.5v is the output of the DAC, so if not here it means the preenf405=>mcp4922 communication is not OK.

The 4 leds are connected in series to the same pin so it's weird one of them does not work. Polarity ?

Can you post a detailed good quality picture of your PCB, that would help.

Do you use an OLED or a LCD display ?
Double check the 68ohm LCD resitor if you use a LCD.
Double check the OLED resistor (22ohm if OLED and direct junction if LCD).

Do you hear a "pop" in the audio when you switch on the preenfm2.

[benjaminr]

Hello!
...ya, sorry for the novel, I think I went a litttttle deep into project mode that night. :S
I'm using an LCD screen, just a cheap one.
Checked the 68ohm resistor with a multimeter and it was bang on, continuity was fine. I shorted the OLED resistor with a resistor leg.
Yes. Sigh. I did install that led backwards.
One thing I'll do is go over the flux again, in the light of the flash on the pics i see that I left alot more on the than I thought.
Haven't tried anything with the preenf405 yet, probably won't get a chance until tomorrow night.
Here's some pics! The buttons I used probably seem like a weird choice, but I make my own panels so little round holes are much easier to achieve with the tools available to me!

[Xavier]

With a LCD display you need the RV1 (variable resistor) to adjust the LCD contrast. Without it you have a black screen.
Do you see some backlight on the LCD when you switch on ?

You also need a USB key with the "pfm2/" folder on it. Else you'll have only white square on the LCD.
Without USB you can press a button while switching on and you'll enter bootloader mode, which will allow you to check the LCD.

[benjaminr]

Oh! Excellent, that's a lead. My screen is blank (no white squares) but is backlit. I'm hoping so hard it's just that my contrast is just "turned down".
Forgot to answer your other question, the preen does make a small pop when powered on (no start up sound though), though I'll check again after work, as I easily coughs have forgotten to turn up the volume pot or something.
I've tried formatting the usb as fat 32 and fat 16, each time putting the pfm2 folder on the root of the drive, but I haven't tried a new usb stick yet. I'll pick one up hopefully today.
Might not get a chance to get to the component store for the variable resistor before the weekend, since I work until after it closes, but I'll see if I can sneak over on lunch or something.
Thanks so much!

[benjaminr]

Ok! So, looks like my screen wasn't blank, just invisible. VR1 did the trick!
May be worth adding a note in the build instructions for other cheapskates like me lol.

But now it seems I'm stuck on the bootloader. It always boots directly onto that screen in the pic (no splash or animation or anything), and no button presses seem to do anything. I've checked all the pushbuttons (including the encoders) several times with a multimeter, and they seem to be functioning properly (open unless pressed, then closed). I have lots of regular tac switches, so I can try swapping them out, but I can't see why the ones I'm using wouldn't work, and it wouldn't work as well for the asthetic I'm going for to match my other panels. Worth a go if it seems promising to you though.

Gonna keep looking for a different usb stick to try, bought a three pack not too long ago, so they gotta be around somewhere.

[benjaminr]

DINGDINGDINGDINGDING!
Turns out im an idiot and wired my buttons sideways, so the Preen thought they were always being pressed, hence bootloader mode!
Flipped them around and it's running great!! Thanks Xavier for all your help, very happy playing with it so far, excited to start programming voices and really lean into it!!