Zvex SHO troubleshooting

[Lost_soul]

Good work! I have many times had to start over on something. When nothing makes sense after hammering on it for a while, a fresh start can be the best choice.

Do check out your switch and wiring to it, as already mentioned. That might have been the issue all along.

Now go make LOUD noises!!   

i will certainly do! but after that i got a huge project of a boss oc-2 that i built and didn't work that i need to solve   hopefully it's just a bad transistor or something. i posted about it here but i will post again when i am finished with this SHO

but overall thank you so much for following my issue until it's done!

[antonis]

but where did you get the 900 micro amps and 200 micro amps from? and you used V=IR to calculate the Vr right? but how did you know the I

I (current) calculated by V (voltage drop across respective resistor according to your measurements) and R (resistor value)..

[Lost_soul]

I (current) calculated by V (voltage drop across respective resistor according to your measurements) and R (resistor value)..

I mean where did you get the current numbers from?

[antonis]

I not sure if here is the right place for Ohm's Law implementation but let's try..

V = I x R => ( 9 - 4.4 ) = I x 5100 => I = 4.6 / 5100 => I = 0.0009 (900μA)
V = I x R => ( 9 - 8 ) = I x 5100 => I = 1 / 5100 => I = 0.0002 (200μA) approx.

[Lost_soul]

I not sure if here is the right place for Ohm's Law implementation but let's try..

V = I x R => ( 9 - 4.4 ) = I x 5100 => I = 4.6 / 5100 => I = 0.0009 (900μA)
V = I x R => ( 9 - 8 ) = I x 5100 => I = 1 / 5100 => I = 0.0002 (200μA) approx.

I know, but how did you get the voltage drop across R4 to calculate the current with?

[antonis]

I know, but how did you get the voltage drop across R4 to calculate the current with?

YOU got that voltage drops across R4 and I simply trusted you..!!!

Look again on your post #34 and my post #41..

[antonis]

You see, what you all need is just a single voltage measurement, either on Drain or on Source..
(or even between Drain and Source..)

e.g.
The current producing 1V across R4 equals the current producing 1V across P1 (considering R4=R1)..
If not, some current from Drain should leak (in case of voltage drop across P1 smaller than that across R4) or be injected on Source (in case of voltage drop across P1 bigger than that across R4 - observable in BJTs of very low current gain..)

You could even calculate working current by measuring voltage drop betweeen Drain and Source despite Drain-Source channel unknown resistance..

Homework: 
For FCCW configuration, suppose R4=10k, P1=2k and V_DS=4.2V. What is the current..??
Then, what is the Drain-Source channel resistance..??

[GibsonGM]

Lost Soul: you measured 4.4V on the drain.   The supply is 9V.  It must come through the 5.1k resistor.   This means the rest of the voltage is dropped by the drain resistor, which is 9-4.4 = 4.6v. 

[Lost_soul]

Now go make LOUD noises!!   

I finished the circuit and the signal and the LED circuits both were working fine until after like 3 minutes of playing the LED went off but the signal was not affected..
I changed the transistor for the LED and everytime i put another one and connect the battery, the LED lights for like 3 seconds and then goes off.
What is happening?

[Lost_soul]

Homework: 
For FCCW configuration, suppose R4=10k, P1=2k and V_DS=4.2V. What is the current..??
Then, what is the Drain-Source channel resistance..??

I understand now. So you got the voltage from my measuring. I thought you got it from some calculations 

I will do the homework tonight

[R.G.]

I finished the circuit and the signal and the LED circuits both were working fine until after like 3 minutes of playing the LED went off but the signal was not affected..
I changed the transistor for the LED and everytime i put another one and connect the battery, the LED lights for like 3 seconds and then goes off.
What is happening?

Something is draining off the pull-up current from the reverse biased pull up diode, most likely. Parallel the one diode with one or two more. Otherwise, we'll have to dig.

Background: the fundamentals of the Millenium involve the fact that a reverse biased diode has a very small, but nearly fixed amount of leakage current. For silicon, this is best measured in nano-amperes. 30 to 40 years ago, fast switching diodes had to have gold atoms implanted in them to be "fast". Gold doped diodes leak 10 to 100 times as much as ordinary silicon junctions, making them perfect for things like nano-ampere pullups. But the silicon got better. Today, semiconductor makers can make "fast" switching diodes without the gold. So modern fast diodes leak less. How much less is unspecified. Generally, another diode or two contribute enough leakage to make it work.

[Lost_soul]

Something is draining off the pull-up current from the reverse biased pull up diode, most likely. Parallel the one diode with one or two more. Otherwise, we'll have to dig.

Why am i facing so much problems with a simple build

Should i do the resistor test you told me about and see what happens?

Should i measure the voltages of the transistor when switch is on and off? Or maybe i need to change the diode rather than connecting it with another one in parallel?

Idk how to connect them in parallel btw.

But why did it work for like 5 minutes if there was something wrong with it!

I was so damn happy when everything went well

I will try to connect 1 or more diodes in parallel (that't gotta go on the solder side tho as i have no space

But for parallel do you go positive to positive and negative to negative or what?

[Lost_soul]

Generally, another diode or two contribute enough leakage to make it work.

I connected 2 diodes on a small board and 2 wires, then i connected the Mil circuit alone with a 9v battery. At first it light up for about 2 minutes then turns off and doesn't turn on again!

So i used the 2 wires and tried to touch them to the diode in circuit and nothing happened.

2 small notes:
When i touched the wires to the 2.2k resistor the LED went on for a split second and then off.

And sometimes when i disconnect and connect the battery the LED also lights for a split second then off.

Here are some pics for main board.

[GibsonGM]

Components in parallel will be same polarity 'touching' each other.  So, + to +, - to -.  They literally go alongside each other.

Can't see the diodes in your pictures to know if they are correct.

Of course, resistors are non-polarized, so it does not matter which way they go. Here is a picture give you the idea, however:




Same for the diodes, keeping the same polarity:

[Lost_soul]

Components in parallel will be same polarity 'touching' each other.  So, + to +, - to -.  They literally go alongside each other.

Can't see the diodes in your pictures to know if they are correct.

This is how i connected them. I put them in a small board with 2 wires just to test before desoldering and soldering.




The picture also include a close up of the Mil board.

[GibsonGM]

They should go on the millennium board, right next to the diode that is there.  As R.G. said, try adding one, then another. Putting them on another board might introduce resistance, voltage drops and so on that might affect operation. 

The long, flying leads add resistance, capacitance and inductance and allow for a few other nasty things - not that they will stop your circuit from working, but these PARASITIC properties are undesirable, so we try to use good build technique to reduce them!   

-----------------------------
I suggest you find an old printer cable, a USB cable or something, and get some nice, small wire that you can work with. It will make your life easier!  I have even used telephone and RJ45 internet cable, for example.  I try to use stranded wire when connecting pots and switches so that they can flex, and use solid core for most other things. It has not been a problem in 20 years of DIY. 

Hang in there, you are learning a lot in a short time, it's ok  

[Lost_soul]

They should go on the millennium board, right next to the diode that is there.  As R.G. said, try adding one, then another. Putting them on another board might introduce resistance, voltage drops and so on that might affect operation. 

But how can i do that with no space left?
By putting them on the copper side maybe? Or do i have to make another small board for the whole thing and act like this one doesn't exist?

I suggest you find an old printer cable, a USB cable or something, and get some nice, small wire that you can work with. It will make your life easier!

I will definitely try to do that as these wires are expensive

Hang in there, you are learning a lot in a short time, it's ok

Indeed man. I already don't understand a lot of this stuff but am trying to grasp any piece of information so when it clicks my head explodes

This is far from i do in life. I am supposed to be a doctor in 3 or 4 years and graduate from medicine but instead this stuff seems more interesting to me. I just need to manage my time to do both.

[GibsonGM]

Yes, you can put the other diode or two on the back side of the PCB, as long as you are careful to not create a short circuit to anywhere they should not touch! 

Most of us here are amateurs at this too.  There are some very well-educated people who help us along (you have been talking to some of them!), and everyone likes to help others, so don't feel like you're doing it wrong.  You're not, you are just learning 

With your background in science, I'm sure you will pick this up quickly, since it requires logic and working through things in steps. You do not have to be a mathematician. You will learn how to organize all of this by just doing more projects and asking questions!    I am a house painter, but I used work in environmental engineering.  That was also not much math, but 'educated' enough to follow along.   Most anyone who is interested will be able to make some good and fun pedals through this forum.

[R.G.]

Mike is giving you very good advice. You can solder them on the bottom, as he suggested.

For something this small, you can also simply bend the leads of the added diode and trim the leads so that when the diode body is on top of the existing diode, the added diode's leads just reach down to the original diode's leads. Then you hold it in place, heat with the soldering iron in one hand and when it's hot enough touch the joint with solder held in your >third< hand.      Then solder the second lead of the new added diode. We call this "piggy backing", but I don't know if that idiom is used in your country.

I spent some time messing with the circuit and looking through datasheets for diodes. My best guess at the moment is that the "leaky" diode you're using is simply too good, not leaky enough. This would account for some of the funny time delay things you're seeing.

Do you have, or can you easily get some 1N4000 series diodes? They range from 1N4002 to 1N4007 part numbers, and are in black epoxy packages instead of the glass packages of the 1N4148/1N914 parts I think you're using. These are 1 amp rated power rectifier diodes, and they may have higher leakage currents than modern signal diodes like the 1N4148. The datasheets say they >>may<< have leakages up to 5uA. They probably won't be that big, but will probably be bigger than the signal diodes. They may work better.

What makes this hard is that the state of the semiconductor industry has made diodes so uniformly "better" that we are reduced to guessing which diodes are leaky enough for a use that is not what they were intended for.

[Lost_soul]

I understand what you are saying Mike. You don't have to know math to know this stuff, one just needs to make his rusty head work around this sfuff. Just need to make more stuff, ask and here comes knowledge 

It's just that i started doing all this 3 months ago and i can't stop going deeper to the level i am afraid that could affect my normal life but i guess i just need to prioritize what's more important.

You and everyone on this forum has been really helping and has a lot of knowledge and tbh i am a little jealous

After i am done with this SHO i will take it slow and do it in my free time as a hobby. And i already learned a lot from you. I will report back when i do what you suggested. Thank you!