README FIRST: How to Request Troubleshooting Help For WTPA2 / Post a Bug Report

edited January 2015 in Decrees From On High
So you've debated and then ordered your WTPA/WTPA2, eagerly assembled it, and found that you have a problem!
Don't worry, you aren't alone. As far as I can tell by guessing from the forum requests and the numbers of WTPAs sold as of this posting, about 7% of WTPA owners run into some kind of trouble in the build process.

I want your WTPA to work. You want your WTPA to work. The following post is about how you can get your WTPA working the way you want as rapidly as possible. Specifically, it is here so that you don't waste your time (and mine) on the forum. It will detail the most common things to look out for when tracking down WTPA problems, and if that doesn't get you where you need to be, it is an instruction sheet for how to make a help request in such a way that I (and the other forum members) will be able to understand what's going on with your situation.
This post is long, and divided into several sections. The first is about tools you can / should use to debug your WTPA. The next is a checklist of things to examine in your WTPA and the associated symptoms that may happen if they are incorrect. These are what I expect you to tell me in your initial request for help. Finally, the last section are some tips about how to accurately convey your information to the forum in such a way as to be useful.

TOOLS (in order of most to least important):

1.) Your Brain.
I'm not being a dick (entirely) here -- I'm serious. I cannot tell you how many people will build something, turn it on, have a problem, and just STOP THINKING. This doesn't just apply to kit builders, it applies to "proper engineers" of all stripes. On a bad day forums (and tech support, FAEs, etc) can exacerbate this, because they present an opportunity to offload your thinking to others. This is the ONE THING that I will not tolerate when answering troubleshooting requests. I understand that you may not know much about electronics, and that you may not have much in the way of tools, and I will never get upset about that. But you have the single most important device you need to solve problems of any kind and I expect you to use it. I *really* want your kit to work and for you to be happy with it! It makes me money and it makes me feel good. However, I expect you to want it to work even more than me, and to meet me half way whenever you can. The experience you gain (though you may not have bargained for it) will be worth way more than the object itself, and it some ways you're lucky. Kindof. But enough of this.

Can't read the resistor code? That's fine, most people can't -- however, I expect you to know how to use google. Now if you were like, "google says that resistors have four stripes but the blue ones in my kit have five -- what does that mean?" -- that question is a _little_ better. You haven't encountered 1% resistors. A google search for "resistors with five stripes" just turned up the answer on the first page for me. Better yet would be: "I know my resistor values are right because I checked the codes but the resistance measurement I get between point (x) and (y) seems weird -- can you explain that?"
Where do I look for power on the AVR / how many volts / which chip is the AVR? Read the schematic. If you can't read schematics, there are lot of helpful sites on the net, like this one:  
ARRL Schematics

Finally, use the forum search as well to see if others have had similar problems to you. They frequently have. A search for "dimensions" or "standoffs" will find you an awful lot about how others have mounted their devices in enclosures, for instance.
2.) The Ghetto Oscilloscope:

Another essentially free and REALLY useful troubleshooting device -- this turns your ears into a several thousand dollar suite of diagnostic tools!
Since WTPA is an audio device, and you bought it, the chances are very good you've got audio cables laying around somewhere. If that's the case this tool is essentially free and you already have it.

Many of the signals floating around WTPA are audio frequency. That means that if you know where and what to listen for, you can understand a lot about what's going on in the circuit by listening to different points.
Make a cable similar to above. Attach whatever amp you use to two clip leads, probes, or bare wires -- I regularly use a 1/4" cable that has two alligator clips soldered to the center conductor and shield (pictured above). These will correspond to hot and common. Attach the common clip (or just touch it) to ground. The tab of the 7805 is an easy spot. Then use the other (tip) connection to whatever you want to listen to.

FWIW, it's possible the "ghetto scope" might get confused by the DC biases in different points in the circuit depending on the amp it's using. It almost certainly won't, but I mention this for completeness. If you're worried about it anyway, you can make an RC filter on the input of the ghetto scope to eliminate the DC component. Real scopes do this to when they are in "AC coupled" mode. Almost all audio amps in the world are AC coupled anyway, especially crappy ones. DON'T use your ten thousand dollar McIntosh as a ghetto scope. I've regularly used a guitar amp (they work great), a crappy rat-shack battery powered amp, my home stereo, a DJ mixer, etc.

Finally, don't get ground and signal connections confused in your ghetto scope; nothing bad will happen, you just risk get incorrect results.

Example: The ghetto oscilloscope can troubleshoot nearly any problem in the audio path of WTPA.
3.) The Multimeter:
These are the gateway drug to all debugging, basically.  Like other gateway drugs, they can also be very cheap.
My buddy Limor at Adafruit sells them:
Adafruit Multimeters

Or you can get one at your local Rat Shack or Frye's or whatever.
You will use this tool over and over again if you do any kind of electronics. They are useful to read resistance, voltage, current, diode drops, continuity, whatever. I own six and use them all.
I won't require you have one, but you should think about picking one up if you don't have one.

Example: You can check to see whether the voltages at all the points in WTPA are what they should be, or whether you made a solder short, or whether a diode is burnt out, etc.
4.) The Oscilloscope:
This device is pretty much a badge of entry to the "serious nerds club". If you have a scope you probably don't need to read this. If you don't, you should know that they allow you to display a voltage against time on a screen, which tells you worlds about what is happening in a circuit. I like older Tektronix analog units from the 70s and before as entry level scopes -- they radiate intellectual integrity, are easy to fix, are cheap, and regularly exceed their specifications even at 40 years old (I've fixed my ancient Tektronix 454 a couple times and it still kicks the ass of many entry level digital scopes in everything except storage).
Most WTPA users don't have one of these, but you should know about them.Example: You can see any audio problem and also check to see what your databus is doing, how long your reference caps take to reach equilibrium, what your bandwidth is generally, etc.
5.) A computer with an AVR programmer and tool suite:You'll need this to flash a bootloader or bring up a chip with no bootloader on it.While you're at it, you can also use it to command WTPA's brain to do specific things which will make troubleshooting a TON easier. This will require some knowledge about programming. Generally this is more advanced stuff than most WTPA users are willing to do, but it is both useful and great fun.Example: You think you have a problem on the address bus on the RAM. You tell the chip to set all the address lines high and then check to see if they are, then do the same for low.


Many of these are symptom specific, so you'll have to figure out whether or not they apply to your problem. When you ask for help, know the answers to the questions below and TELL ME.*Did you not read the manuals?
Then you shall have no pie.
*Does WTPA power up?
If not, check the voltage at the input of the regulator and then at the output. Should be anywhere from 8-16v for the input (based on the supply you're using) and about 5v for the output. If it's low, you probably have a short on the board somewhere, or a broken chip. If it's fine, start checking elsewhere (like at the AVR).
*Does WTPA pass audio through?
In ANY mode, will WTPA get an undistorted signal from the input to the output? Does it get any signal through? This path is distinct from the sampling path, and this is a really easy way to tell whether or not your problem is in the audio realm or the digital realm. 
*Does WTPA perform the self-test as detailed in the manual?
This tests the DAC, the switches, the AVR, and the control pot -- and the data latch to some extent. If WTPA behaves correctly here and generates a sawtooth wave whose pitch is directly related to the setting on the pitch control pots, this tells us a lot. If the self test works but sampling does not, you likely have a RAM problem. If there's no sawtooth wave, you likely have a clock or DAC problem. If the lights are screwy you have an AVR, databus, or LED problem.
*Have you, even for a little bit, hooked up more than 5v to the REGULATED side of the system?
All bets are off if you got a 9v battery onto the board somehow. None of the chips are spec'd to run at that voltage and this is the only situation in which broken ICs are a likely suspect.
*If the self test and all the above work, and you're having trouble with some feature what does it do exactly? What works and doesn't?
IE, if realtime works and so does MIDI sampling, but normal "caveman" sampling does not, the relaxation oscillator is a likely suspect. Very often if all of the above work OK and some sampling goes screwy you either have an intermittent connection or a RAM bus problem.
*ARE YOU SURE your cables are hooked up right?
This is embarrassing and seems stupid, I know, but MANY of the problems people report are connection problems. Seriously. It happens to me all the time, even. 
*If you're grasping at straws, have checked the above, and still have no idea, check the following things:--Triple check component values. They're easy to get wrong.-- Make sure you have a clock at pin 20 of the AVR. You should be able to hear it.-- Make sure you don't have dead batteries. No end of trouble comes from that. Use a wall wart of >350mA and 9-12vDC.-- Make sure you know how to count the pin numbers on an IC -- if you've never done it, it isn't always intuitive.
OK, so you've done your best to interpret the schematic and can answer all the above questions. Now what?Send a post telling the forum exactly what you tried and what you've found in a detailed way. If you don't tell me you did something, I will assume you didn't do it. This is not a dick move, it's the safest way of troubleshooting. Although naturally, if you tell me the self test operates as detailed in the manual, you don't need to tell me the board is getting power.

Title your post intelligently and specifically, and start a new one. Don't follow up on somebody else's old post that may or may not be related to your problem.
The title: "Problem with Low Supply Voltage and Intermittent Reboot" is a good title. It will help others with similar problems.The title: "Oh Noes" or "Broken WTPA" is a terrible title. It conveys no information to me or anybody browsing the forum. It is annoying and makes you look like you play WoW.If you have the ability, making a video or audio example of your problem and posting a link to it can be REALLY helpful, but if you do this, make sure what you are showing us is clear.DON'T use Wolf Eyes as your signal source and tell me you have a noise floor problem. Don't just randomly turn knobs and expect me to get what you mean.DO write down exactly what you are doing and why you did it, and preferably record the transition from "everything is fine" to "this is messed up".
@friesandgravy did an outstanding job of doing this thoroughly and awesomely in the following post, which I am referencing as an example:
Please, don't talk like a LOLCAT. Seriously. It makes it hard as hell to understand technical minutia.
Finally, if I'm slow about getting back to your post it means I'm busy. It's like when Gandalf split from the Dwarves for a few weeks and they got all pissed off about it, but actually he was taking care of some really important *ish.Like paying my rent or making new instruments.
In light of this, it is OK to "bump" or "nudge" but not to make snippy comments.If I'm taking too long for your tastes, the best way to get me to reply faster is to reply to your own post with new work you have done to try and solve your problem. This will generally make me feel guilty because it will appear to me that you are diligently and patiently bettering yourself and the world and I am letting you down.It may take a little work to do this, but you might just solve your own problem!
In general: be patient, be diligent, be inquisitive, be critical, and have fun!
July 21 2009 (revised for WTPA2, January 3, 2014)
PS -- a bug report is different. It means that your WTPA works but that something is wrong with the code. If I've done my job it will be really hard to find these.
Example:When I record in Bank 1 and hit "Backwards", the sample does not play backwards.
That's a real bug.In general I *LOVE* hearing about this because it reflects on the way my brain works, and it is an opportunity to make everybody's WTPA a little better.
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