General deubgging help

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General deubgging help

Postby DarkNDubby » 02 Apr 2012, 23:42

Hey everyone, I am now being harshly reminded what a noob I am. I finished building a Fuzz Factory and a OCDv3 using these vero layouts:Image Image
Both of them have been checked and rechecked against the vero layouts multiple multiple times. They both work in bypass mode. They both are basically dead when switched on, though the LED works and it seems like the board is getting some power because there is occasional hissing, popping, etc, when I twiddle the pots. I've spent weeks tinkering with it. I've been reading through forums to try to get some clue as to what I may be doing wrong, but it has real started to expose some noob gaps in understanding and has made it impossible for me to troubleshoot further. So rather than ask some specific questions about the projects at hand, i am hoping that you guys might be able o help me with some general questions to help me help myself...

So here goes:
- How easy is it to fry a transistor? How can I tell if my transistor is fried? I have a Cen Tech DMM that I bought from BYOC's site, can I use that to test? - I see a lot of people are testing the values on the transistor. How do I do that? Is there a resource you can point me to so I can understand what is going on and how to test?
- If I use the continuity test on the DMM, can I touch input and output on the vero and should I get a reading? Or am I supposed to test small segments at a time?
- Is it likely that I could damage other components? For example, can I ruin an electrolytic if I put it in backwards? Or can I just turn it around and it will work fine?
- Are there any tutorials out there that talk about using a DMM for troubleshooting in general? I have looked up videos and the manual, but they didn't help me much.
- Is it possible to overheat components and make them non-operational? Sometimes, I turn up my 5-40watt soldering iron close to full once I start to troubleshoot because i find it is much easier to desolder when the iron is hotter.

Sorry for all the terribly noob questions. I have been reading all over this site and others, but I am still a little lost. I guess I just need the basics of trouble shooting. Any answers or resources you can point me to would be greatly appreciated. I'd really like to grow and get better. (And not be so lost and frustrated...)
-
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Re: General deubgging help

Postby PokeyPete » 03 Apr 2012, 03:26

DarkNDubby wrote:So here goes:
- How easy is it to fry a transistor? How can I tell if my transistor is fried? I have a Cen Tech DMM that I bought from BYOC's site, can I use that to test? - I see a lot of people are testing the values on the transistor. How do I do that? Is there a resource you can point me to so I can understand what is going on and how to test?
- If I use the continuity test on the DMM, can I touch input and output on the vero and should I get a reading? Or am I supposed to test small segments at a time?
- Is it likely that I could damage other components? For example, can I ruin an electrolytic if I put it in backwards? Or can I just turn it around and it will work fine?
- Are there any tutorials out there that talk about using a DMM for troubleshooting in general? I have looked up videos and the manual, but they didn't help me much.
- Is it possible to overheat components and make them non-operational? Sometimes, I turn up my 5-40watt soldering iron close to full once I start to troubleshoot because i find it is much easier to desolder when the iron is hotter.
Sorry for all the terribly noob questions. I have been reading all over this site and others, but I am still a little lost. I guess I just need the basics of trouble shooting. Any answers or resources you can point me to would be greatly appreciated. I'd really like to grow and get better. (And not be so lost and frustrated...)
-

WOW!!!! You don't ask for much, do you? :lol:

1a.) Resistors control the amount of current flowing through a transistor. They are selected based on desired parameters
and the limits of the transistor. If a circuit has a collector resistor of 12k (12,000) ohms of resistance and you make a
mistake and insert a 12 ohm resistor.....yes you will fry it.
1b,c,d..etc.)It appears your meter has a transistor tester built into it. Testing is simple. Turn the selector dial to "hfe".
There is a socket for npn and pnp transistors with labels EBCE for each one. These correspond to the transistor legs.....
emitter, base, collector. It is laid out for two primary layouts....EBC and ECB. The reading should tell you the gain. If it
is not in the range you would expect, then it's bad.
2.)A good way to test continuity is to use the smallest setting on your resistance scale (ohm). Put one probe on point A,
the other on point B. If it reads a short ( 0 ohms ) then you have excellent continuity. If you read anything higher, then
there is resistance in the path. This is an excellent way to test the cuts on your vero boards. Dial in a resistance setting,
place the probes on opposite sides of the cut and read. It should show high resistance (infinite) on a good cut. If there is
a small sliver of trace left you will read a low or "0" resistance.
3.)The simple answer is "yes". Almost assuredly with diodes. Caps....I've seen caps in backwards and worked somewhat.
They could probably be turned around and still function. But this was in a low voltage situation. My advice is be careful
and not do that!
4.)Basic DVM is rather easy to use. There are three main functions: Ohms; Volts (DC and AC); and Amps.
To read resistance (ohms) use the lowest scale for most accurate reading, if it goes off the scale switch to the next highest
scale. When using this scale make sure the power is off on the device being tested. Place the probes across a
component and read the resistance....easy!
Volts: DC and AC. If you are going to stick the probes in you house wiring outlet, make sure to have the selector dial
set for AC Volts.....don't do that! For stompbox circuit select DC Volts 20. Clamp the black probe to a ground connection.
The circuit will be live to test voltage. Carefully place the probe at strategic locations and measure the voltage. These
locations will be like the collector of a transistor, or the base of a transistor. You could place the probe on the voltage
supply rail to make sure it's there. Most of the time your voltage readings will be in respect to ground, so I can say for
the most part just clamp the black probe to ground and read away with the red one. One thing though, be extremely
careful with that red probe and do not touch two points with it.....you will cause a short in a live circuit and can do much
damage.

Amps: Mainly used when breadboarding a circuit. It measures the current flow through a divice, circuit, etc. It requires
that you break the circuit and insert the probes at either side of the break. The meter actually becomes a part of the
circuit in this case, but it does allow you to measure current if you need to. Most of the time you can just calculate the
current and actual measuring is not necessary.
5.) Overheating.....most definately yes. Easy to do with germanium transistors especially. Components can be damaged
from overheating by too much current flow. They can be overheated by taking too long to solder. That's why some people
use sockets for delicate, rare, etc. components. When soldering transistors, you can take precautions like clamping an
alligator clip or hemostat to each leg as you solder. They will act as heat sinks while you solder. Place the heat sink between
the solder point and the main body of the component so any excess heat will warm up the heat sink before it reaches the
component body.

I hope this makes sense and helps a little. I don't have time to proof read it, so there are probably lots of errors.
Hopefully you can make some sense from it anyway, and get something out of it.

PP
“No man is so foolish but he may sometimes give another
good counsel, and no man so wise that he may not easily err
if he takes no other counsel than his own. He that is taught
only by himself has a fool for a master.”
–Hunter S. Thompson

For this message the author PokeyPete has received thanks: 3
DarkNDubby (03 Apr 2012, 16:57), Duckman (05 Apr 2012, 00:13), Greenmachine (04 Apr 2012, 04:34)
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Re: General deubgging help

Postby DarkNDubby » 04 Apr 2012, 20:33

Thanks for the guidance, Pokey, this was so helpful. :D I feel like I have something to try...

So can I ask, as practical application, if I am getting no sound out of my OCD, but it works in bypass. The LED lights up, and it sounds like there is power to the board, just no signal getting through, how would I want to trouble shoot?

Would I do the following (Assuming I am already working off a verified layout) :
1. Do the basics, double check components are in right place and orientation, cuts are correct, connections are clean, no solder bridges, wiring is correct, and solder connections look fine.
2. Do a continuity test by touching 2 places along short segments to make sure the signal is going all the way through using the DMM set on smallest on the ohm scale
3. Check health of transistors, If not socketed, desolder them from board and plug into DMM on hfe setting? Or would I use DC Volt 20, touch black connection on sleeve of input or ground on board and test EBC of transistors for voltage readings to determine health?
4. Check health of IC? How would I do this?
5. Check health of caps? Electrolytic first assuming they are more likely to fry given polarity? Is this right? How would I test to make sure those are still working?
6. If none of these solves the problem, throw it into a pile labeled "uncolved mysteries"?

Sorry for the heavy questions. I've done a bunch of poking around in the FAQ section and through search of this forum, but I was unable to find the answers I am sure there are other here that can benefit from the answers. In hopes of rebuilding my confidence, I built another circuit last night, but encountered the same problem. It works fine in bypass, LED lights up when I switch on, but no guitar signal coming through, just static sounds when I turn the pot. I've got parts for 4 more builds, but my confidence is in the shitter. I just have no idea what I am doing wrong...

Many thanks to Pokey and to anyone else who can throw a bone to this passionate, yet frustrated noob.
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Re: General deubgging help

Postby PokeyPete » 04 Apr 2012, 23:17

DarkNDubby wrote:Would I do the following (Assuming I am already working off a verified layout) :
1. Do the basics, double check components are in right place and orientation, cuts are correct, connections are clean, no solder bridges, wiring is correct, and solder connections look fine.
2. Do a continuity test by touching 2 places along short segments to make sure the signal is going all the way through using the DMM set on smallest on the ohm scale
3. Check health of transistors, If not socketed, desolder them from board and plug into DMM on hfe setting? Or would I use DC Volt 20, touch black connection on sleeve of input or ground on board and test EBC of transistors for voltage readings to determine health?
4. Check health of IC? How would I do this?
5. Check health of caps? Electrolytic first assuming they are more likely to fry given polarity? Is this right? How would I test to make sure those are still working?
6. If none of these solves the problem, throw it into a pile labeled "uncolved mysteries"?

1.) check
2.) check
3.) Before doing the drastic stuff, do the easy stuff first. Measure the voltages at the legs. Typically the collector is connected
to the supply rail through a collector resistor. If the transistor is not turned on (no base current) then you'll read the supply
rail voltage on the collector. Since no current is flowing through the resistor there is no voltage drop across it and you will
read the supply rail voltage on either side of the collector resistor. If you read a voltage on the collector that is less than the
supply rail voltage, then you know that you are getting some base/emitter current flow.
4.) One simple answer is to replace it. However, if there's a fault on your board that destroyed the IC, then replacing it without
correcting the fault first will only result in destroying the new IC as well. So, do a little testing first. Do a voltage test at select
points. Is V+ correct? Is ground connected? Check the voltage readings on the legs.....do the readings match what you see on
the adjacent part (check schematic)? Get (buy or build) a signal tester and learn to use it. Look for any readings that are
abnormal. Sometimes schematics have voltage readings at select points or test points. Sometimes members have posted their
voltage readings so you can compare yours to theirs.
5.) Caps are hard to kill unless you drastically exceed their voltage rating. They can get old and dry out. Just check the cap
values and orientation and make sure they are correct.
6.) I would suggest going over the boards very carefully. Make sure the component placement is correct. Make sure that you
made all the cuts correctly on the vero boards. Did you notice the hard to see cuts under the components? Check your cuts
with a magnifying lens for completness (or do the continuity test across each one). You're just trying to rule out an on board
problem. Besides switches and pot connections that are onboard, they only offboard connections are typically the V+, ground,
in, and out. Some of these go through the stompswitch.....so....if your bypass is OK, but the board is not working (and has
been carefully checked and your sure it should be good to go) then the problem may be just a case miswiring. Easy to do!
You mention BYOC. Go to their site and look at one of their project instructions. They have a method of case wiring that is
probably consistant with all their builds. Follow it on your construction. Madbean has a method of case wiring. Both are
good....they may look a little different but amount to the same thing. Does your case wiring match one of these?
“No man is so foolish but he may sometimes give another
good counsel, and no man so wise that he may not easily err
if he takes no other counsel than his own. He that is taught
only by himself has a fool for a master.”
–Hunter S. Thompson
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Re: General deubgging help

Postby Nocentelli » 05 Apr 2012, 10:56

I've found the fastest way to debug is to use an audio probe: The drawback is you need to have a basic understanding of the schematic and how it has been translated into vero. I've got a very basic plastic breakout box with an in jack, out jack, and a DPDT toggle switch. The toggle is the bypass, so I can easily check that the guitar signal is actually being sent to the amp as it should. There is a hole in the side of the box with two colour-coded solid core wires protruding, blue for send from the guitar input and yellow for return to the amp. I just hook the blue input wire to the effect input, then follow the circuit from input to output whilst strumming until the signal disappears: It is soon very apparent where the problem is. Additionally, the sound you get as you encounter problems gives you an idea about the nature of the problem. For example, touching the yellow wire to the blue at the circuit input should give a sound identical to the bypass: Moving to the yellow to the other side of the input cap should sound very similar unless you're using a tiny cap.Moving to the base of the first transistor there should be no change in sound: From here, move to the collector - If there is silence you have a pinout issue, or the emitter or collector are not connected properly. If you've got signal but seems quieter (it's usually louder) that's often a pinout issue. In general, total silence often indicates something is grounded when it shouldn't be, hiss/noise/crackle etc usually indicates a dodgy connection. The fact that you get noise from the circuit when the knobs are moved indicates nothing other than the output of the circuit is connected to the amp, to find the fault you need to identify where the INPUT signal disappears.

I know it's late in the process to suggest this, but it always pays to breadboard the circuit first: This serves many purposes, firstly checking you actually like how it sounds, secondly verifying the schematic is correct and sounds how it should, thirdly it ensures that you know how the circuit works and are confident on how the components must be laid out: it's very easy to overlook stuff if you're building-by-numbers, breadboarding forces you to prove to yourself you can make it work without worrying about dodgy soldering being a possible cause.
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Re: General deubgging help

Postby DarkNDubby » 13 Apr 2012, 17:33

Thanks Pokey & Nocentelli - sorry I went dark... crazy week at work...

So I finally came across the Geofx page which gave me a clearer understanding in addition to both your input. I feel like I have a few more tools to help myself, though I haven't been able to get those two circuits working. At least now I know what to test for and better how to ask for help. Thank you both for taking the time. I cannot wait to get these circuits working...
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