AMZ Mosfet building problem

[Tamir]

well well, I built the circuit again and it went very very good, solders are best. not that the effect works, but not I have many space between the components (the first circuit I build exactly with the spaces that the layout shows - as you see, it is very very very close and small so it was hard to debugg.).
I still get the silence when I plug the pedal - no bypass, so what I think is first to do - is rewire everything, but it looks good to me, eh. if after that I get troubles it has to be the circuit (I didn't check for voltages yet on the new veroboard).

I will give you answer soon, I need to relax, being a loser is exhausting 

[Tamir]

OK, i did try different combinations of wiring on the jacks but I didn't get true bypass! it means the wiring is still wrong,
the new voltages are
D = 4.46
G = 0.71
S = 4.74

The gate is still not ok i understand, but maybe it is because of the wiring? how can I at least solve the wiring solution? 'cause if I don't have it, it doesn't matter how great is my circuit.

thanks you all, you are great.

[gaussmarkov]

hi tamir,

i'm sorry that the second one didn't work out.  but now you have two, and you can compare them as you go along debugging.

you are quite right, wiring is often the problem.  either things are connected somehow that should not be or the components are not exactly placed correctly.  i find that checking continuity (beep mode) is a good method for finding problems with wiring.  to do this it helps to have an understanding of the layout and the schematic.  to help you with this, i have put some labels on dragonfly's image:



maybe you could check my work to be sure that i haven't made a mistake?  all of the strips on the vero layout correspond to "nodes" in the schematic with two exceptions.  first, the ground node actually spans two strips.  second, the 4th strip from the top has 3 nodes:  input, output, and A.  i have tried to follow some of the labelling in jack orman's original schematic.  so A is located where his A is and i have called another point "Vr".

in a vero layout like this, checking that all of the components on a particular node are hooked up is easier than on other layouts.  but that is one of the things that i check as i build, that all the things that connect to a particular point really are connected.  i use the DMM continuity check to do this.  with a vero layout, you can just look and see whether the components are connected to the proper strip.  a better check is to actually do the continuity check from lead to lead, not using the strip itself, because this checks the quality of your solder joints.  you should get a strong clear beep in every case.

i also use the continuity test to make sure that things that are not on the same node do not have continuity.  again, with a vero layout like this one, this is relatively easy:  you just make sure that none of the strips are connected to any of the others (with the exception of the two ground strips that should be connected).  also make sure that the input, output, and A sections are not connected.

another way to do a similar check is to check continuity across components.  the two leads of a resistor in this circuit, for example, should not pass a continuity check.  otherwise, there is a connection, or a "short", somewhere.

another source of errors is using the wrong value of a component.  resistors are the easiest to check:  measure the resistance of each resistor on your completed circuit with your DMM.  if it does not read close to the required value, then there is a mistake related to that resistor.  unfortunately, one cannot check capacitors this way.

i ask that you do these checks and fix any errors that you find.  one error that you already know about that continuity tests will uncover is that your bypass wiring is not working.  in bypass, there should be continuity between the tips of the two plugs (guitar cable and amp cable).  trace the connections from one tip to the other and find the places that the connection is broken and make corrections.  as far as problems go, this is one of the easiest to fix so we had better be able to straighten it out together! 

to be able to help you further, i think we are going to need complete voltage readings when your battery is hooked up.  that is, please tell us the voltages at every single node.

good luck, gm

[petemoore]

OK, i did try different combinations of wiring on the jacks but I didn't get true bypass! it means the wiring is still wrong,
  While Back I decided to work boards first, as basic as possible no jacks then add anything after the board seems to work. Working one stage at a time, this ciruit has one.
the new voltages are
D = 4.46 [ I suspect will change when the source is made to be within operational bias.
G = 0.71  [...
S = 4.74  [shouuld be a 2k7 resistor from ground, that makes the voltage reading at the source closer to ground, the 2k7 pulls it toward Gnd.
  Using data sheet on "X' transistor, the layout and schematic, verify the Qpin wired as source is source is connected to the boards source connections [you used socket?]
The gate is still not ok i understand, but maybe it is because of the wiring? how can I at least solve the wiring solution? 'cause if I don't have it, it doesn't matter how great is my circuit.
  ot: Basically the thing has to work when wired right, can't work when not,
Using your first response to "What to do when it doesn't work" as a template for every future response is a good idea, saves anyone reading...having to go back and find early info, try to remember what changed with your circuit etc. right now I've forgotten what transistor you've used...amending a complete rundown of the circuit will make it easier for people to compare early and late data entries...and by looking at the latest debugging data speel, anyone can find the info desired quickly because it is all categorized. Cut 'n Paste, then adjust the texts as the circuit changes, marking new entries with symbols like '*' !!

[Tamir]

Ok, I checked some things
Every thing that should be grounded is grounded fine - 1&2 of pot, sleeves etc.
the two tips connections on jacks are connected (beep), but I am not shure these are the tips, I am still confues about those, anyway.
the two ground strips are connected fine by the jumper (beep)
and the output and input are not connected, or connected to A (as it should be - the cut traces are good). hmm, on the switch itself, I put the leads of DMM on the first legs - the input-output legs and it doesn't beep as well.

what do you mean strips should not be connected? the components are connecting them, as an example, the first and fourth strips are connected because of the 2.7k resistor.

I don't know about the resistor, I mean, I know to read 'em by colours... and they are 4% exception so it should be ok, right?
I say again - instead of 62k I soldered 47k+22k (69k), if it matters.

and I made a mistake, the drain is 4.76 no 4.46.

[gaussmarkov]

let's see ...

OK, I checked some things
Every thing that should be grounded is grounded fine - 1&2 of pot, sleeves etc.
the two tips connections on jacks are connected (beep), but I am not shure these are the tips, I am still confues about those, anyway.

i was referring to the tips of the plugs, not the jacks.  if you put the plugs into the jacks, then you will see which part of the jack touches the tip (the very end) of the plug.  that is the part of the jack that we label the "tip" connection.

the two ground strips are connected fine by the jumper (beep)
and the output and input are not connected, or connected to A (as it should be - the cut traces are good). hmm, on the switch itself, I put the leads of DMM on the first legs - the input-output legs and it doesn't beep as well.

hmm.  have you found any information about how the switch works?  do you understand how the connections are made inside the switch? 

what do you mean strips should not be connected? the components are connecting them, as an example, the first and fourth strips are connected because of the 2.7k resistor.

i mean that there should be no continuity (beep) when you touch one probe to a strip and the other probe to another strip.  a signal will get through when the circuit is working, but there shouldn't be a "short", or a connection that works like a simple wire.

one thing I noticed and seems not so good - the ground and 9v+ strips are connected (beep).

good for you!  you have found the symptom of a mistake.  can you find the connection?  what about the other strips?

I don't know about the resistor, I mean, I know to read 'em by colours... and they are 4% exception so it should be ok, right?
I say again - instead of 62k I soldered 47k+22k (69k), if it matters.

i was suggesting that you read the resistors with your DMM.  you can still read their values with the DMM even though they are soldered into the circuit as long as there are no continuity mistakes.  that is the reason for checking continuity and discontinuity first.

and I made a mistake, the drain is 4.76 no 4.46.

alright.  we cannot use that information until we are sure that everything that should be connected together is and everything that should not be connected is not.  but it is great that you are being careful.  debugging requires that kind of care.

all the best, gm

[Tamir]

Here is the checklist to fill out:
1.What does it do, not do, and sound like?
2.Name of the circuit = AMZ Mosfet Booster
3.Source of the circuit
http://aronnelson.com/gallery/album18/AMZ_MOSFET_BOOST_VERO

5.Any parts substitutions? If yes, list them.
Did not have a 62k resistor, so I soldered 47k + 22k (69k) is series.

6.Positive ground to negative ground conversion? No

7. When the battery is not connected to the clip, when I put the DMM leads on the clip I get 0.00

Voltage at the circuit board end of the red battery lead = 9.45 (as the battery's_
Voltage at the circuit board end of the black battery lead = nothing (it is the ground strips, isn't it?)

Q1: BS170
D = 4.76
G = 0.71
S = 4.74

[petemoore]

Here is the checklist to fill out:
1.What does it do, not do, and sound like?
2.Name of the circuit = AMZ Mosfet Booster
3.Source of the circuit
http://aronnelson.com/gallery/album18/AMZ_MOSFET_BOOST_VERO

5.Any parts substitutions? If yes, list them.
Did not have a 62k resistor, so I soldered 47k + 22k (69k) is series.
This resistance will need to be adjusted...after the source looks ok.
6.Positive ground to negative ground conversion? No

7. When the battery is not connected to the clip, when I put the DMM leads on the clip I get 0.00

Voltage at the circuit board end of the red battery lead = 9.45 (as the battery's_
Voltage at the circuit board end of the black battery lead = nothing (it is the ground strips, isn't it?)

Q1: BS170
D = 4.76
G = 0.71
S = 4.74
  The pinout of the BS170...not that I can see what you have going on there....this is a culprit to many an Fet problem.
  The source pin should read ~2k7 from ground.
  Pull the battery, measure every resistor. Test every ground. Verify every connection and that no extra connections are made. Verify all polarized components orientation. Do that with the Vero Layout and the Schematic...[again, as I guess you already have...]...somewhere in there is a miswire or wrong resistor or...the source should find a voltage near ground with the 2k7 pulling it toward ground, or pinout problem.

[Tamir]

hello sorry but I didn't have time to check everything, I hope you did not stay and wait for me 
well, kind of good news! I understood what was the problem with my wiring and now I got bypass!  weehee to me, I can't say it is not a transparent clean effect!

now, Everything (POT, both jacks and components) are grounded fine, ask my beep mode and I know everything is connected as it should be (except the .1 and .001 caps that maybe I changed between them, but from what I understood it should not be my problem).

you told me to check the resistors with the DMM, so I tried, but since sometimes on this layout there was two components on the same strip I made A solder that contains both legs of the comp's, for example ('cause I realy don't know how to explain)



so if I soldered components like that, I think that's the reason why I CAN'T read the resistors with the DMM, except the resisor that should be 100k but for some reason I read 47k~ and the 2k7 resistors that I can read and they are ok.

thanks a lot, if you have more ideas just say so.
BTW - tomorrow  I will get new resistors from my friend.
BTW 2 - when I play with bypass and then pust the footswitch, I can play for 3 seconds and then I have silence because the effect is not working.

[petemoore]

  Yes...if you get a lower than marked on color code reading of a REsistors resistance in circuit, you may want to find if there's an alternate current path through the circuit, bypassing that resistor if so...
>  Do the math and figure it out
or>  Get two same value resistors and test them offboard to see what that reads offboard...
or>  Lift one end of the resistor illiciting an 'anomolous' DMM reading in circuit, re-measure it with one end lifted.

[Tamir]

I changed some of the resistors (and checked with a DMM) and it still not working, something wierd, when I play on bypass and then switch to boost I can play for another 3-4 seconds and hear myself but in very low volume... and then still nothing.

For some reason I think that's because the effect doesn't get the power from the battey but I has some for another few seconds... yeah I know it is stupid but it happend to me few weeks ago with my Boss.
but from what I see the battery seems to be connected good. and the voltage on point A is between 4.5 - 5 as it should by so I think the bias is fine.

[petemoore]

  FIRST:  Kudos for consistant/rational debugging efforts !!
Bias is a voltage 'relationship' or ratio between the three pins, ie you can maybe get 4.5V on the drain and still have a misbias issue.
  AFAIKTell that 100k should read 100k, the only alternate path is through the capacitor paralleled to it, and no DC should pass through that cap.
 

[Tamir]

then what do I do or check now?

[petemoore]

then what do I do or check now?
  Judgeing from previous fixes, It is quite likely something missed in previous tests...so...the same thing again.
  post the most recent 3 transistor pin voltages measurements again?
  D = 4.76 [would be ok...
G = 0.71
S = 4.74  [but the source V is right next to Drain V,
  The source is near ground, R wise and hence V wise. 2k7 is a relatively small Resistor, and is what pulls the source V to near ground.
  If you have spares, and have the Q socketted, perhaps bending the S/G legs out in opposite directions a touch, then around each other to swap their pin positions...
  The reason I say this is because the Gate is real near Ground @ .71v,
  Measure every resistance from G to....
  Same for S to ground
  ...And everywhere else, apply the meter in any way which you think some reading should look...attach one lead to something, then radiate probe touches of the other lead from that point, testing for R readings, also for continuities/and importantly NON continuities...where applicable according to schematic.

[Tamir]

My BS170 voltages is still same but a little lower because of the battery.
didn't understand what you said about the transistor (and yes it is socketted).
did the regular continuity checks and it seems to be ok excapt a thing I noticed... when the black lead of MM is on the 3 strip from bottom, and the red is on ground / third strip from top - it beeps, but if I change the order (of the MM leads) it doesnt, same with the first and last strips (9V+ and ground)


this is exhausting...

[petemoore]

  'Beep mode' is actually a diode checker, in one direction the diode should beep with the DMM leads attached, if the diode is good, then in the opposite direction it should not beep. Also a number can be seen which is the foreward threshold voltage of the diode.
  when the black lead of MM is on the 3 strip from bottom, and the red is on ground / third strip from top - it beeps, but if I change the order (of the MM leads) it doesnt, same with the first and last strips (9V+ and ground)
  you are testing the diode, and it's good.
  ,,,not the good way to verify pinouts, but...I suspect there may still be a mis-pinout causing troubles, at the source and gate, it is possible to bend the S/G pins around one another [to reverse there assigned pins] and plug it back into the socket. If everything's right it has to work, if any one thing isn't, it wont.
  I need to check, but a 2n7000's [check again, I'm sure you have already..] 'unbent pins would put the transistor pins as shown on the layout, and the 'face' [print on the Q] of the transistor would be facing left/west.
  So the drain pin stays straight, the S/G pins need to bent 'around' each other, I find bending one at an angle, the other to an opposite angle, then around each other so they can trade pin assignments...is an easy enough way to try the pinout.
 

[Tamir]

I am using BS170
this is the pinout of the bs170 (I am sure you knew it but for making sure)


according to this, the face should be to the left, as it is... 
oh, everything is ok... ok sucks.

I want to add something, I realy can't decide. what the effect should do is give me a clean boost (but it have to give a little gain ofcource).
when I play on bypass, and then switch to effect, now I can play but in a lower volume with phenomenon that I get a little gain but not so nice and alternatively. I mean, some times it has gain, and some times not, some times when I pick hard on the strings it does noises to my amp, and it is always low volume. one thing for sure, the POT doesn't do anything.

How can I realy make sure if the effect is actually working and does what it needs to, or it is just a mistake on the circuit?

[petemoore]

  For some reason the source still looks to high a voltage, that 2k7 should be pulling it to nearer ground.
  Gate should be higher, pulled up a bit by the huge 10m resistor.

[Tamir]

I am pretty sure the 2k7 resistor is ok, so what can be the problem, wow, I almost give up  to destroy another effect circuit. yeah.

[Tamir]

Bumpy bump.
this circuit doesn't have any chance, does it?