What to do when it doesn't work

[RjM]

Sparkleboost

Q1

D- 0.01
G- 0.02
S- 0.01

So... What do these readings mean? Can anyone assist me?

This means that you're not getting any +9V to the JFET, or so little that it doesn't matter. Something is such a high resistance that not enough current gets through the JFET to pull the source up by the volt or so that would start turning the JFET off and let it stabilize, so it just sits there saturated.

Second step: Use your voltmeter, negative lead clipped to ground and probe the +9V on the board (wires to batteries break), the top of the 100K pot, the wiper of the 100K pot, the bottom of the 100K pot, and the drain of the JFET. Yep, we're walking down that conductive string, looking for where the voltage stops. When we walk past the end of the 9V, we have just passed the problem.

Alright, I fixed a problem, (incorrectly wired power jack) but I think there is another problem present now. Here are the new, current voltages.

Q1

D- 5.38
G- 0.07
S- 2.05


When I turn the effect on, the volume is cut in half. The gain pot doesn't seem to do anything, but the volume pot does. I replaced both pots, by the way. This is suppost to be a boost, so I don't think that the drop in volume is a good thing... heheheh. Also, there is a light crackling/ static noise in the background when the effect is on.

Anyone who knows what to do about transistor readings, could you assist me?

[petemoore]

A well thought out page on basics for debuggers would be a blessing.
 Kudos for taking this one by the horns RG!
 We're all typing after all, this is sure to be a real time saver.
 It is already 'mandatory for classic debugging' that certain measurements be made and analyzed.
 This is certain to lead newer electronicians to other questions, but at least they'll be certain to get at least a small taste of some immediate results and more, which can best be found by reading on!!!
 [Unless you have an EE that likes to read to you,... bedtime stories].

[RedHouse]

This is bound to draw fire but.... Baww Humbug.

The usual "oldbee" rant, oldsters that have answered the "same old - same old" question too many times always want a new rule, but that would be counter productive to this hobby. In fact when we grow tired, we must just let someone else answer, let's not agree to be harsh and quelch the questions.

(no disrespect intended, I'm over 40 myself, built my 1st Fuzz in 1971)

There is such a wide range of interest/knowlege/ability in a forum like this, and indeed it can/does wear on the executive membership to answer the never ending questions that have been answered 1k times before (yadda yadda yadda, blah blah blah) ....BUT... ya know what, for the poor bloke that just got here ...lets take a deep breath and (yes, one... more.... time)  point folks to the proper resource without gipes....

....it's what we do!



Thank God for Aron, RG and all the rest here (the list is like way tooooo long to type)

[TheBigMan]

Excellent idea!

Might I also suggest a paragraph or two on the use of an audio probe for debugging as well.  I know that the diagrams on your site and Paul's are posted often, which invariably leads to a follow-up question of "What does that thing do and how do I use it?"

[jmusser]

I think a lot of this comes out of frustration, especially if you've been screwing around with a circuit several evenings and have gone through the circuitry, and can't seem to resolve it. You're just hoping that someone will say something that might cue you in to something you haven't "really" looked at. Especially when you're a newby, and you've tried too advanced of a circuit for your skill level. I know, because I've been there. About every time, mine's miswired somewhere, because I got in a hurry, or was really too tired to finish the circuit, but did anyway. The only problems I've come up with lately, were a couple of Tim's octave up circuits that are correct to the schematic, but don't act like they're supposed to. Then I fished around and was told that transistors of different gains make the difference. That's something I had no clue to look for. Anyway, I know people like RG and Mark Hammer get frustrated, but you are appreciated for all your wisdom. I have learned a lot from you two alone, and things are getting clearer because you took time out to explain things in a way I could understand. The "Super Fuzz" thread the other day where you went through the features step by step, is just such an effort. Mark went through diode "flavors" the awhile back. Because of your responses along the way, I'm not having to ask "those type" of questions like I used to. :wink:

[Alpha579]

Sparkleboost

Q1

D- 0.01
G- 0.02
S- 0.01

So... What do these readings mean? Can anyone assist me?

This means that you're not getting any +9V to the JFET, or so little that it doesn't matter. Something is such a high resistance that not enough current gets through the JFET to pull the source up by the volt or so that would start turning the JFET off and let it stabilize, so it just sits there saturated.

Second step: Use your voltmeter, negative lead clipped to ground and probe the +9V on the board (wires to batteries break), the top of the 100K pot, the wiper of the 100K pot, the bottom of the 100K pot, and the drain of the JFET. Yep, we're walking down that conductive string, looking for where the voltage stops. When we walk past the end of the 9V, we have just passed the problem.

Alright, I fixed a problem, (incorrectly wired power jack) but I think there is another problem present now. Here are the new, current voltages.

Q1

D- 5.38
G- 0.07
S- 2.05


When I turn the effect on, the volume is cut in half. The gain pot doesn't seem to do anything, but the volume pot does. I replaced both pots, by the way. This is suppost to be a boost, so I don't think that the drop in volume is a good thing... heheheh. Also, there is a light crackling/ static noise in the background when the effect is on.

Anyone who knows what to do about transistor readings, could you assist me?

well, first off, bias the drain to 4.5v with the trimmer...what jfet are you using? might be a good idea unplugging the power and meauring the resistance from source to ground...check and double check all your wiring carefully...

[R.G.]

The following is a “how-to”, step by step procedure for getting the most help fastest when your newly soldered up effects circuit just doesn’t work. The material is copyright 2005, R.G. Keen, and is displayed on diystompboxes.com by permission. Permission is not granted for redisplay from other web sites without permission in writing from the author.

Gather the things you’ll need
A full set of information about what you built
1.Name of the project: Example: Neovibe, from General Guitar Gadgets.
2.Links to the source of the project â€" web site with the schematic or project, layout and wiring diagram. Example : Neovibe
3.Some candid admissions about how closely you followed the suggested layout, if any. If you just perfboarded it, say that, and if you can, include a picture of the board. Scanners do a GREAT job of making pictures of PCBs, by the way.
4.Any parts substitutions or modifications you made to the original. If you didn’t have any 10uF caps and used 22uF, say that. If you had to use a 2.7K resistor instead of a 2.2K, say that. If you used a BC109 instead of a 2N3904, say that. By the way, if you substituted any transistors, it’s a sure bet that the first question you get asked will be “Did you check the pinout of that transistor?” Delight the questioner by saying (truthfully…) “Yes, I did a google search on that part number and check the pinout against how I soldered it in.” If you can’t say that, chances are good that you’ve already found your problem, all by yourself.
5.Whether or not it’s a positive ground circuit like a PNP fuzz or a Rangemaster that has been hacked to work with negative ground. This is a special case, but a common one. “Positive ground” means that the positive/red lead of the battery clip is connected to signal ground. “Negative ground” means that the negative/black lead of the battery clip is connected to signal ground when the effect is operating.
6.What it does and does not do â€" how it works; partially or not at all. For instance, if it lets no sound through; or if it makes a harsh, distorted sound only when you strum hard on the strings at full volume; or if everything is really, really low volume.

An electronic meter capable of reading 0-20Vdc and with an ohmmeter scale. This can be analog, but digital ones are available for as little as $10.00. I’ve seen them as low as $2.99 here in Austin Texas in 2005. If you have to, borrow one. There is really very little anyone can tell you that would help if you can’t measure and tell them what voltages you get. It will be much easier if your meter has some way to clip the negative/black lead to circuit ground instead of having both leads with only points. Most meters do. If yours doesn’t, you could use a clip lead to do this, if you have a clip lead. Here’s a quick guide to how to use a meter in simple laymans’ terms. (to be added â€" RGK)

A non-dead battery. Measure the battery with the voltmeter. If it’s not over 8.0V, it’s going to gum things up and give you inconsistent results. Get a fresh one. Using a DC wall wart is problematical. What if it’s the wall wart that’s bad? Get a good battery.

A calm, open mind. I don’t like to admit this in open company, but one of the deepest episodes of rage I ever felt was when I had been flogging this one poor circuit board to death and even though all the hookup wires and parts were in the right place, nothing worked â€" for hours. I was almost speechlessly angry â€" until I noticed that I was debugging the bottom side of the board for access to all the solder points and had neglected to put the ICs in the sockets. The madder I got, the LESS capable I was of noticing the real problem. You gotta clear your head first.
Being absolutely certain that everything is correct and it still won’t work is not good preparation for noticing an errant solder thread, for instance. Mother Nature does not lie, but she is a stickler for details. If it was put together perfectly, it would work. It not working is Mother Nature's way of telling you that you made some tiny error, and it's no reflection on you if it's not perfect the first time.

When you have everything gathered, but before posting, get the specific information you’ll report.
1.Hook up the DC power to the circuit (no input signal or amp needed) and clip the meter black/negative lead to signal ground. Probe **every** pin of each IC, transistor and zener diode (if any), and also the battery at the clip and  where the battery wires come onto the board. Make a written list of the voltages. Below is a helpful starter list of the minimum things to measure.
2.For extra credit â€" search the forum archives for problems with the same circuit. Someone else may have had exactly the same problem.

(d) Now post. Post all of your gathered information along with the list of voltages along with a request for help interpreting them. Chances are, someone will spot the section that’s not running correctly right away. Then a few more secondary tests will likely have it nailed. You’ll be posting it to a forum where most of the people there will have been through exactly the same situation. They want you to be successful, and they don’t think you’re stupid or not cool for having a problem with it.

(e) Learn. There are certain things that always determine what's working and what's not. Read the postings of others that have posted their voltages and find out what happened to them. That way, you get the benefit without having to make the mistakes. Search the archives for problems with the same circuit. Read the debugging page for the indicators about what voltages indicate about function. This last takes a long time, but it's the most rewarding. If I had had a similar forum to learn debugging in when I started this, I’d have wasted a LOT less time in my life.


That’s the procedure.

Here is the checklist to fill out:
1.What does it do, not do, and sound like?
2.Name of the circuit =
3.Source of the circuit (URL of schematic or project) =
4.Any modifications to the circuit? Y or N
5.Any parts substitutions? If yes, list them.
6.Positive ground to negative ground conversion? Y or N
7.Turn your meter on, set it to the 10V or 20V scale. Remove the battery from the battery clip. Probe the battery terminals with the meter leads before putting it in the clip. What is the out of circuit battery voltage?  =>
Now insert the battery into the clip. If your effect is wired so that a plug must be in the input or output jack to turn the battery power on, insert one end of a cord into that jack. Connect the negative/black meter lead to signal ground by clipping the negative/black lead to the outer sleeve of the input or output jack, whichever does not have a plug in it. With the negative lead on signal ground, measure the following:
Voltage at the circuit board end of the red battery lead =
Voltage at the circuit board end of the black battery lead =

Now, using the original schematic as a reference for which part is which (that is, which transistor is Q1, Q2, etc. and which IC is IC1, IC2, C1, and so on) measure and list the voltage on each pin of every transistor and IC. Just keep the black lead on ground, and touch the pointed end of the red probe to each one in turn. Report the voltages as follows:

Q1
C =
B =
E =

Q2
C=
B=
E=

IC1 (or U1)
P1
P2
P3
.
.
.

D1
A (anode, the non-band end) =
K (cathode, the banded end) =

D2
A =
K =

Z1 (zener)
A =
K =

And so on until you get through them all. Having gathered the data, post a tidy list of it on the forum, and you’ll most likely have a working effect soon.

For extra credit, while you’re waiting for someone to tell you what they see, probe the pins of each of the electrolytic caps, verifying that the voltage on the (+) pin is more positive than the voltage on the (-) pin. If it’s not, that cap will eventually fail, whether it’s the immediate cause of the thing not working or not.

Yes, it is a pain. But it is a time tested, effective, highly productive pain.

Do this a few times, and you’ll start to know ahead of time when something is wrong. You’ll be far down the road on learning.

(I can add more material on what to look for in terms of what the voltages mean, but I think if we had this at a minimum from people seeking help, we’d nail about 99.99% of them.)

Howzat??? What did I leave out??

[sir_modulus]

Looks good!

I have one addition....check to see if your input/output wires are not reversed. I've never rebuilt a circuit because I hooked up the I/O wires wrong internally.....more than once :oops:

Cheers,

Nish

[RjM]

1.When I turn it on, the volume is cut in half. The gain knob is unresponsive, and the volume pot does work.
2.Dragonfly's Sparkleboost
3.http://www.diystompboxes.com/sboxforum/viewtopic.php?t=28818 ; http://img.villagephotos.com/p/2004-7/770357/SPARKLEBOOSTPERF.gif
4.No mods
5.3K9 subbed for 2K7, 10K pot for 5K,2.4M for 2.2M, MPF102 for NTE458, no indication LED
6.No
7.No battery

Q1;MPF102
D = 4.78 (its as close I could get it, it should be 4.5v)
G = 0.06
S = 2.02

Meter set to 20k ohm; no power to circuit for these measurements
D = 4.24
G = 0.76
S = 4.09

[keko]

I want a schem 4 that thar MechaBlitz SuperBasher!!



RDV

RDV, you have to read more carefuly. The quote said that the schem was at www.JoesToplessBurgerAndEffects.com

:twisted:

[R.G.]

OK. We have a sample case.
=============================================

1.When I turn it on, the volume is cut in half. The gain knob is unresponsive, and the volume pot does work.
2.Dragonfly's Sparkleboost
3.http://www.diystompboxes.com/sboxforum/viewtopic.php?t=28818 ; http://img.villagephotos.com/p/2004-7/770357/SPARKLEBOOSTPERF.gif
4.No mods

OK so far. But

5. 3K9 subbed for 2K7, 10K pot for 5K,2.4M for 2.2M, MPF102 for NTE458, no indication LED

As I said, the first question I'll ask is if you checked the pinout of the subtituted part against the original.

I did. See http://pubpages.unh.edu/~aperkins/pdf/MPF-devices/MPF102.pdf for the datasheet, and notice that whether or not the MPF102 and the NTE458 are the same pinout, the MPF102 is pinned GSD and the layout is for SGD. If it is wired exactly like the layout, the gate and drain are reversed.  A quick look at the NTE458 has the SGD pinout.

Did you allow for that when you wired it up?

6.No
7.No battery

? You need a battery. Does this mean that you are powering it from a DC adapter in spite of the admonition to use a battery?
Also, you have not supplied the voltages of the red and black wires from (what should be) the battery. These are important, as they verify that the battery voltage has made it onto the board OK. We really need that info.

Q1;MPF102
D = 4.78 (its as close I could get it, it should be 4.5v)
G = 0.06
S = 2.02

Hmmm... I'm trying to think what would happen in that circuit if the gate and source were reversed. It ... might... give you those voltages.  

Meter set to 20k ohm; no power to circuit for these measurements
D = 4.24
G = 0.76
S = 4.09

I'm not sure why you did these. I only asked for voltages. Good commentary though - I'l clarify that.

So - can you check the things where I asked for more?

[RjM]

Alright. I'll do some measurements and post them later.

[R.G.]

... Baww Humbug.  The usual "oldbee" rant, oldsters that have answered the "same old - same old" question too many times always want a new rule...  indeed it can/does wear on the executive membership to answer the never ending questions... for the poor bloke that just got here ...lets take a deep breath and (yes, one... more.... time) point folks to the proper resource without gipes....

That is one viewpoint. I disagree with it and here is why.

(a) It works. The product of several thousand iterations of helping people with things like this is the recognition that there is a small set of things to do that will solve the greatest number of these problems.  I used to ask people things like what color their soldering iron was, how thick the box they had the effect in, who manufactured the wire, etc. (that's a joke...) and then I moved on to Freudian analysis: How did it feel when you turned it on? Did it seem to you like it *wanted* to work? Then there was my Vulcan period, when I asked people whether they assembled the parts in a logical sequence.

The upshot of all that was that when I just asked people the DC voltages, I usually got a set of voltages that pointed more or less immediately to where the problem was. Eventually, I quit asking everything else. As the more experienced among you recognize, the list of stuff to do is really just "list me the voltages" and enough window dressing to get that done well. Knowing how the parts have to work and what the voltages are is sufficient for every flaw except RF oscillation. It works.

(b) This discipline in and of itself is a valuable resource for beginners - right up there with learning what negative and positive are. As you point out, beginners are, by definition, lost. We help them find things. This is one of the most valuable things to find. Add to it signal tracing, and you have enough skills to keep up with most of the professional lab techs that I ever had help me.

(c) On a philosophical basis, while you and I were brought up to question authority and bah-humbug rules as the aged person's response to change and and attempt to keep order in a changing world, it ain't always that way. I once managed a software department where about half the work was mind-numbingly repetitive although devilishly complex and about half was junior-Einstein debugging. When I got there, the practice was that the
people who did the complex-but-repetitive stuff were under seige every week because there would be some tiny error that crept through. They learned this process by rote, like Kunta-Kinte's ancestry, and although they were good, sometimes they made errors. We were pilloried by the rest of the software group for this about weekly.

I tried putting the junior Einsteins over there to help. What do you think this dose of pure problem solving did for us?

Yep, you're clever - then we were in trouble **daily**. Creativity and problem solving was NOT what we needed.

I sat everyone down and told them that I wanted a detailed step-by-step written checklist of every step in their many-and-several processes delivered to my office the next day, and that hereafter, every single weekly cycle would have a full set of checklists filled out, checked and handed in to me for filing. Not knowing me, you have no idea how bad that tasted to me - or my staff.

But they did it. No one spoke civilly to me for two weeks. Then we had a little situation where we were accused of fouling things up because we had missed pieces that were supposed to go in. "Ah" I said, "not so. I have this little signed and dated checklist of what we did and... hmmm, yes, *your* department didn't turn in the code. Looks like *you* fouled it up."

That happened twice and suddenly people spoke civilly to me again.

That laborious blather is one way of saying - there is a time and place for rules. Rules can either be soul stifling chains on our minds, or they can be simply huge time savers and ways to allow our minds to work on what really needs worked on. Do you *really* want to think about how to make coffee every morning? Or would you rather just remember "Put in two coffee measures, fill with water, and punch the button"? Rules can and have been misused by the old, the entrenched, the boring, (insert favorite group here) to oppress and deny the human spirit. Rules that *work* are really really good things to know if you understand why they work.

IMHO, this set of rules is in the second, useful direction.

Now... lesseee... where is that cultural revolution handbook?

[NaBo]

I don’t like to admit this in open company, but one of the deepest episodes of rage I ever felt was when I had been flogging this one poor circuit board to death and even though all the hookup wires and parts were in the right place, nothing worked â€" for hours. I was almost speechlessly angry â€" until I noticed that I was debugging the bottom side of the board for access to all the solder points and had neglected to put the ICs in the sockets.

thank god im not the only one who's done this...  :lol:

[Fret Wire]

That's an awesome debugging checklist/primer!

Maybe these are trivial: but....

under posting the link to the schematic, a reminder/disclaimer that many schematics on the net of the same ckt are bad/unverified. Might remind the person who is helping to check an unusual schematic against a known verified one.

under parts substitutions, list any components that have been scavenged. Nothing wrong with the practice, but some components like electro's may be bad, or IC's/jfets could be heat/static damaged during removal.

under the pnp/npn fuzz thing, if the ckt has Ge trannys, the person should post their gain/leakage if known, and which was placed in Q1, Q2, etc.

Of course, all of this requires as much discipline from the helper as well as the person seeking help. Not only in being patient and encouraging, but in staying on track with the problem. There has been some threads where the person is having a problem, and others are offering their favorite clipping diode mods. This checklist would guide the helper as much as the person seeking help. A person needing help will naturally follow the advise that sounds like the easiest, quickest fix for their problem, so we need to stay on track when we're helping.

[Phorhas]

R.G. wrote:
I don’t like to admit this in open company, but one of the deepest episodes of rage I ever felt was when I had been flogging this one poor circuit board to death and even though all the hookup wires and parts were in the right place, nothing worked â€" for hours. I was almost speechlessly angry â€" until I noticed that I was debugging the bottom side of the board for access to all the solder points and had neglected to put the ICs in the sockets.


thank god im not the only one who's done this...

We should open a support group... man I remember how pissed off I was at myself not succeding in solving this problem... when I found out the the d*mn IC was winking at me from across the table I didn't know if I should laugh or dry... so I did a bit of both

Trivial Mistakers Anonymous

how many times did you run through every trace, connection and wire, searching of a short, just to find out that the batt. is resting quitly far far away...

[David]

I want a schem 4 that thar MechaBlitz SuperBasher!!



RDV

I think that's probably the only pedal with 18 gain stages.  :twisted:

Ohhh, yeah!  Doesn't that have the 18 stages of discrete diode-compression op-amps using MPSA13's as the NPN transistors?

[aron]

I would add to read the FAQs as well as the debugging page:

http://www.diystompboxes.com/pedals/debug.html

http://www.diystompboxes.com/cnews/FAQ.html

http://www.geofex.com/effxfaq/fxfaq.htm

[jmusser]

As usual R.G. good stuff. Another oops I really enjoy, is when I'm scratching my head, and find out that the plug is only half way into the jack on the effect. :x

[petemoore]

Debugging is a process of eliminations.
 Suitable PS?
 Grounds made?
 Certain 'things' like this MUST be determined/eliminated to move on to more circuit specific questions...on ANY powered circuit, every powered circuit...well for 'effective' traditional debugging...which is the method we all use...if a better method pops up, let me know...
 So barring new DB techniques, the debugging process of elimination DEMANDS these things be looked at anyway, whether we crotique each individual post for 'missing' content, or just state unequivacally that they must be included...'My knob don't work'...not much I can type about a thread like that except...
  The usual debug 'necessities' be included.
 Pretty much universal to all powered circuits.