AMZ Mosfet building problem

[gaussmarkov]

hmm, sorry, what cord? didn't know about it, I just soldered the wires.

squidsquad is just refering to putting the plug into the stereo jack.  plug=cord in this case.

[petemoore]

  If you're using the input jack as a power supply lift...
  stereo 1/4'' phono input w/V+ to ring, sleeve to circuit ground, open [no *mono 1/4'' plug connecting the stereo jacks ring/sleeve] the power supply circuit is lifted.
  Insert mono 1/4'' plug into a stereo jack wired like this and the power supply circuit is completed.

[Tamir]

oh, I am realy stupod forget to do it.
drain voltage is about 5.06~

now I get numbers, more details?

[squidsquad]

Your guitar cord...into the fx's input....which connects the battery (when wired properly).

[Tamir]

Yeah yeah, I understood it. what details can I give you now except the drain voltage?

[gaussmarkov]

Seems like a straight forward layout, read the "What to do when it doesn't work" stickie and
come back with some voltages etc, that will help solve it MUCH quicker that just "It dont work"

more voltages (source, gate, ...). 

[Tamir]

Seems like a straight forward layout, read the "What to do when it doesn't work" stickie and
come back with some voltages etc, that will help solve it MUCH quicker that just "It dont work"

more voltages (source, gate, ...). 

maybe something I do understand?
wow, I am sick of not  understanding you guys, I tried the wiki and stuff but I can't find answers to all of these, so don't be mad at me, I guess it will come with the experience. 

[gaussmarkov]

ok.  here's more information on reporting voltages.  in your circuit there is a single field effect transistor (or FET), the BS170, which has 3 terminals called the drain (D), the gate (G), and the source (S) terminals.  you have now successfully measured the voltage at the drain terminal at about 5V, which is where it should be according to Jack Orman's on-line article about his circuit.  the point A that Jack refers to connects to the drain of the FET.  the "what to do when it doesn't work" stickie gives the example of reporting voltages for a transistor with 3 terminals labelled C, B, and E (collector, base, and emitter).  in your case, you should report the D, G, and S voltages.

you should also measure the voltages (relative to ground) of the two ends of your diode (even though logically those voltages are covered by the G and S voltages of your FET--that's how you debug--they might not be the same).  and you should report the voltage at the point marked Vr in Jack's diagram.

best wishes, gm

[gaussmarkov]

here's a useful item you may not have noticed:  the third link at the top of forum pages is called the "Debugging Page."  you should also read that.  especially take the time to make the audio probe.  this will be an indispensable tool for your debugging.  i just used it yesterday to find a missing connection on something i was breadboarding.  i had forgotten to hook up the supply voltage to an IC.

all the best, gm

[Tamir]

ok thanks a lot
D = 5.06~
G = 0.56 (~)
S = 0.04-0.06

mm the diode leads are in the same strips, but anyway the minus is as the G and + as S.

[gaussmarkov]

ok thanks a lot
D = 5.06~
G = 0.56 (~)
S = 0.04-0.06

mm the diode leads are in the same strips, but anyway the minus is as the G and + as S.

great.  now here's another item that has helped us all:  "the search function is your friend."  if you use the forum's search function and enter the words "amz mosfet boost voltages" then you will find this thread where these voltages are discussed.  more searching gives this other thread. 

you will see that there can be lots of confusion, even about this fairly simple circuit.  there are issues about getting the pinout of your transistor correct.  you have to check on the transistor for who made it and look at their datasheet.  and you will see R.G. and Joe Davisson both comment that the Gate voltage must exceed the Source voltage for the transistor to conduct (you have that part right). and Doug H comments that you need at least 2V at the Gate to turn the transistor on (he looked at a datasheet to find this out).  that is a problem for your circuit, your G voltage is way too low.

so recheck the value of your resistors (with your DMM) and--i mentioned this above--read the voltage at the point marked Vr on Jack's schematic.  it's the spot between the 100K and the 62K resistors.

all the best, gm

[petemoore]

http://www.muzique.com/schem/mosfet.htm
  I'm trying to work on figureing this thing out, so correct my typing please, and tell me what it is you're about to do that I'm Suggesting, that way I can decide whether you should seek better advice before letting me screw up your circuit, disregard if my personal test [which may or may not help] isn't what you wanted to read.
  >IIUC< [and welcome any corrections]
  C1 blocks DC at the input. the Mosfet input is so high impedance = current flow is so small it can be disregarded FPOTDiscussion.
  The circuit works without the protection zener diode.
  The 10M pulls the gate up, smaller values will pull harder [I'd persue fix first tho].
  The 100k/62k is a 162k divider..you could just string those two series without the rest of the circuit, connect V+ and Gnd. as shown to battery, and measure...something above 1/2v...these are there to provide a voltage through which the 10m is able to hold bias on the gate, the 62k is a socket in the case of my mosfet boost, a socket in which I plugged a 100k linear pot so I could dial up easily R value there, measure and replaced with a fixed Resistor.
  The Drain resistor, 2k7, allows the drain to be less than 9v, and turns some of the current flowing from S/D into voltage for output. It is the drain bias resistor. C4 blocks DC at the output, may be used to cut lows if made a smaller value.
  well...there's the top half, the bottom half is about the source, the 2k7 , Jack Orman says:
  The source resistor is bypassed by a large capacitor in series with a variable resistor used as a gain control. The minimum resistance setting yields maximum gain.
  Because the 10uf allows for current to flow at *'frequencies which the Mosfet boost will be expected to amplify' with it's gain pot set at 0.0k, it's *'effectively like having the source grounded' , the source resistance is used as a gain control, limiting S/C channel current flow.
  I just take the dogmatic approach, connecting the DMM to D, then testing that C4 is Beeping', and 2k7 is measure between D and V+.
  Then connect to V+, and measure the 62k.
  Then Ground, test all shown grounds, measure the 100k, and turn the pot up then measure the 2k7.
  Then check the gain pots resistances [turning the potshaft/ measuring R's]..
  Measure the 10m...
  observe the polarity of the zener and C5.
  Hope this Helps !!!
 

[Tamir]

the search function is your friend

Are you telling me? I am Linux user!
ofcource I used the search, But I didn't know what the voltages even mean and especially that they are wrong.

I have read the posts you gave me and Jack's arcticle, and since this layout doesn't use a trim, I can't tweak, but read that I can do it with resistors changes. anyway, in the first page of the topic, I said that I didn't have 62k so I used 22k+47k, I guess it is not so different so it won't work.

now, I want to check "point A" as jack said to, but I don't know where it is on this layout
http://aronnelson.com/gallery/album18/AMZ_MOSFET_BOOST_VERO

as I understand it, it is the 4 strip from upside between 2k7 and the Drain pin.

[petemoore]

  Point A on that layout is still the transistor's Drain Pin, where the 2k7 is connected.
  The 62k almost certainly will need it's value adjusted.
  You can lift one end of the 62k, then clip a 100k lin. pot wired as Variable resistor [wiper and one outside lug] to determine the resistor value which brings 1/2v to the transistor output [drain]. Then unclip and measure the set 100k pot's value and find a fixed resistor [or two] that equals that value and install it.
  Having the '62k' as an easily adjustable Resistance makes biasing a Mosfet boost point A, easier.

[Tamir]

I will check all that you said in the evening, but I have a question, why don't get bypass even the effect itself not working? isn't that true bypass? (yes it does)
and I didn't understand how to connect the pot... which leg goes to?

[gaussmarkov]

the search function is your friend

Are you telling me? I am Linux user!
ofcource I used the search, But I didn't know what the voltages even mean and especially that they are wrong.

yes, it can be frustrating to know that the information is out there but you do not know how to find it.  i have certainly experienced that.  the "friend" quote is one that appears on this forum all the time and it can sound sarcastic.  i apologize for that.  my point was to show you how you could use the search function and find some of the information that you seek.  you know about searching but not how it could help you in this case.  you are working on the "amz mosfet booster" and we have been talking about measuring "voltages," so i wanted to help you to see that putting those 2 things together into a search of this forum would get you some of the information that you are looking for.

I have read the posts you gave me and Jack's arcticle, and since this layout doesn't use a trim, I can't tweak, but read that I can do it with resistors changes. anyway, in the first page of the topic, I said that I didn't have 62k so I used 22k+47k, I guess it is not so different so it won't work.

now, I want to check "point A" as jack said to, but I don't know where it is on this layout
http://aronnelson.com/gallery/album18/AMZ_MOSFET_BOOST_VERO

as I understand it, it is the 4 strip from upside between 2k7 and the Drain pin.

precisely.  i did explain this above, perhaps badly.

you have now successfully measured the voltage at the drain terminal at about 5V, which is where it should be according to Jack Orman's on-line article about his circuit.  the point A that Jack refers to connects to the drain of the FET. 

we all understand how easy it is to overlook something.  this happens all the time.  especially at the beginning it can be difficult to know where to focus your attention.  hang in there with this circuit and you will get it to work and you will have learned a lot about how to make the next one.

one of the other things that i noticed while using the search function for you is that at least one  beginner started similar threads and got no response.  that can happen because this forum is a busy, slightly random place.  i hope you don't get discouraged.

[Tamir]

sorry about the up but i think it's not over.
well, i am confused right now, so what I ask is, maybe should I give another try and build the circuit again? if yes, what are your suggestions or advices?
I can't stand building things and they don't work, I almost give up...

[petemoore]

1  Count the number of connections at each node.
  Measure every resistor with DMM, just prior to it's install.
  test as you go. look also for 'extra connections around newly made ones
repeat step one each time you move to the next node.
  Treat each mark on the schematic as there for it's reason, cap and diode orientations [the diode[s can be tested].
  I appreciate the time and effort you've done with the board, the circuit has to work or not work when conditions dictate.
  I've had the second build work And show what was up with the first board...
  you can be 4 minutes away from discovering a cause of a circuits malfunction at any time you are debugging. 
   

[Tamir]

just before I go to waste another money and parts ( Just kidding, it's cheap and I have some stock), can you tell me why don't I get true bypass even the effect is not working? isn't that what TB is all about?

[gaussmarkov]

yes, you are correct:  true bypass works even if the circuit that you are bypassing does not.  if your true bypass is not working, it is not wired correctly.  you can use your DMM in beep mode  to find the missing connection.  put the switch in what you think is true bypass and then find the place that your input jack's tip fails to connect to your output jack's tip.  you could have a problem at either jack or at the switch.

you haven't finished debugging your circuit yet, right?  you have a problem with the voltages on the G and S legs of your transistor and there are some things you can do to find the problem.  unless i missed it, you still need to tell us the voltage between the 62K and 100K resistors (strip 2 counting from the top).  can you check the resistance of 10M resistor?  a lot of DMMs don't go that high.  have you checked the direction of the diode?  the banded end should be connected to strip 5 (counting from the top).

also, let me recommend again that you make an audio probe.  you can use it like the beep mode of your DMM to see where you audio signal is (and is not) present in your circuit.  you would use it first to check that the signal appears at the input of your vero board.  if not, then your input jack isn't wired correctly.  then you would check strip 5, to make sure that your signal is getting through that first capacitor.  then check at the drain of your transistor (point A)--except right now there won't be anything there because your transistor is not turning on with the voltage so low at the gate of your transistor.  finally, you would check whether the signal is getting through the last capacitor to your output connection.

you could build the circuit again, and you might get the second build to work.  my advice is to get this circuit working.  it seems to me that you have already learned a lot from the debugging that you have done so far.  petemoore is right, of course, to say that one often learns from the second build what was wrong with the first.

good luck, gm