MXR Micro Amp, from General Guitar Gadgets.

[markbee]

Ive build a clone of MXR Micro Amp, its rather simple project and people recomended it to me. I followed this pattern http://generalguitargadgets.com/projects/15-boostersrouters/70-mxr-microamp-project . Im totally new to all this so you can imagine how much of a noob I probably am. I finished everyting just yesterday and the pedal does nothing. The signal doesnt eve get through the pedal in bypass mode. Its completely dead. I dont know where to start with searching for mistakes, Ive checked the wiring and it is ok. The only thing I changed was 22M resistor, I couldnt find it anywhere so I used two 10M and connected them paralely.
I dont know what to do, Im frustrated as hell. I will appreciate any help or advice. Thank you

Here are some photos if it helps you to see some mistakes or so. Wiring is messy but im sure its correct.

http://imageshack.us/photo/my-images/407/fotografie0655.jpg/
http://imageshack.us/photo/my-images/696/fotografie0656.jpg/
http://imageshack.us/photo/my-images/846/fotografie0664.jpg/

[twabelljr]

It is hard to see the switch and jack wiring, but not having signal in bypass suggests something is wired wrong or the input is shorted. The 2 10M resistors you have wired in series is fine. If you can get the bypass sorted out and the pedal still does not work, post your voltages following the "DEBUGGING.." thread.

[markbee]

http://imageshack.us/photo/my-images/20 ... e0665.jpg/
http://imageshack.us/photo/my-images/33 ... e0668.jpg/
http://imageshack.us/photo/my-images/85 ... e0671.jpg/

here are some other pictures if it helps

[arma61]

Hey looks like you IC is backward, the dot, pin 1, shoudl be towards the top of the board, where the wires are connected to.

also if you can use socket for IC, just to be sure you don't overheat them.

Ciao

[markbee]

ok, thank you. Yo think thats all?

[arma61]

All ? who knows 

Let's say that with a wrongly placed IC surely it cannot work. Reverse it and let us kow.

Ciao

[Mark Hammer]

He notes that there is not even any bypass signal, which suggests something more than the IC orientation (although that will clearly have implications).

Possibilities?

1) Much like JFETs, you would figure that, with only a few lugs, there are only a few possible ways to misconnect a stereo jack.  And you would be wrong.  There are 837 ways to miswire a jack. 

2) Beginner builders often apply way too much heat to the stompswitch, and that ends up melting the grease inside, causing it to flow over the contacts inside and insulate them from making electronic contact.  You can fix this by taking the switch apart, cleaning the melted grease off the rocker contacts, and re-assembling.  Not for everyone, and certainly not a dyed-in-the-wool cause of your difficulties.

[markbee]

Ive been careful while soldering not to apply to much heat on the stompswitch and I think the wiring should be ok, ive checked it multiple times and its alrigh according to generalguitargadgets. So what would you do in my situation?

[arma61]

He notes that there is not even any bypass signal, which suggests something more than the IC orientation (although that will clearly have implications).

Right Mark, didn't read that, just opened the picture and compared and saw the reversed IC... 

So what would you do in my situation?

I'd leave the switch and possibly the jack for the moment, you need now to know if your board is working properly

I suggested this some weeks ago to another forum-mate

"" Try the easy way, or the way I'd do (and I've done  )
leave out the switch
leave out the jacks
connect + to the board
connect - to the boards and to other 2 spare wires
using a pencil make a ring on your 2 spare gnd wires an put these rings directly on the barrel of the cable coming form the guitar and on the barrel of the cable going to the amp.
do the same rings for you input and output wire and put them on the tips of the above cables
(optional, though recommended,  fix the rings with some electrical tape so they don't move)
connect yout battery/adaptor to + and - goind to the board

so now we know if the circtuit itself is working..... then slowly slowly and one at the time we can add jacks and switch.
""

.....last but not least

.... Wiring is messy but im sure its correct.

never say that!!           

Ciao

[markbee]

So I tried to check continuity on everything and it seems just fine, but the components on pcb are not responding to the continuity test, whats up with that?

also the LED diode does not seem to respond

[arma61]

you cannot check for continuity on components soldered to the board, you'll could get wrong reads, just measure the voltages and post them.

[stezza]

it seems the simplest thing to do is make sure signal is getting from the input to the board and to the output when bypassed. There must be something wrong with the witing of the jacks or switch. Get the thing bypassing and then worry about the board. I can't open the second lot of images of the switch/jack wiring.

[twabelljr]

I can't see the second set of images either. Plug a cable into the input and output. Connect one end of your meter to the tip of the input cable and make sure there is no continuity to ground (the enclosure or the cable sleeve). Check continuity from the input tip, through the switch, and to the tip of the output in bypass mode and find where it is shorted or open due to a mis-wire or faulty switch. In bypass you should have continuity from input cable tip to output cable tip. When the pedal is engaged you should have continuity from the input cable tip to the "in" pad of the board. The bypass is the easiest part of the circuit to debug. at this point and since it does not work it is most likely the main problem right now, (other than the I.C.) especially since the led does not illuminate either.

[markbee]

here are the fixed links

http://imageshack.us/photo/my-images/854/fotografie0671.jpg/
http://imageshack.us/photo/my-images/339/fotografie0668.jpg/
http://imageshack.us/photo/my-images/201/fotografie0665.jpg/

[mmaatt25]

My favorite tool for debugging ( and I have a lot of practice) is an audio probe.
Simple to make, have a look at GEOFEX.
Feed the input of your faulty pedal with a signal or plug your ipod into it. Connect one lead to ground on your pedal and the other lead to input of the pedal (the audio probe should be plugged into an amp/speaker/pa so you can hear it) and you should hear the signal. Work your way through the circuit until you don't hear any signal and there's your fault (or one of them any way).

Matt

[twabelljr]

Does your input cable tip have continuity to the single red wire or the yellow wire on the input jack? It looks like you have the yellow as your bypass circuit and it seems to be wired right at the switch but looks like the single red and yellow may need to be switched at the input jack lugs. Yellow should go to tip. I am comparing to a stereo jack I am holding and THEY MAY be different (hard to tell from the pics) so you really need to check with a DMM. Continuity from input tip, through yellow wire to switch, across the red jumper to the other yellow wire, and the to output jack tip. The output jack looks correct, so maybe try working bacwards from output tip with DMM also. *I am still focusing on bypass at this point* It looks like you followed the switch wiring diagram at GGG, correct??

[petemoore]

  Simple little things, but a lot of them.
   The wire and the other wire make a circuit if..connected to a source.
  You want boost and 'fancy' switching, in a box.
   Since the chips been reverse polarized, the easy way to test is with a new chip, chances that it's damaged outweigh the cost of another.
  Then it's a matter of more reading and testing. The user requirements are set by ma nature, the schematics showing sets of circumstances under which she's required to follow ohms law, she does this consistantly.
   Switch wiring alone is complicated', until switch wire-testing finds some things out:
  With 3pdt switch it's easy to make the 3 isolated TPT 'rows' oriented as 'columns', in which case unwiring the switch and turning the body and lugs 1/4 turn is required.
   Electromechanical switch wiring is best explained by the schematic, in my case the details became clear with a bypass box, switch and DMM to verify the marks shown in the diagram, also to test that no new 'nodes' were created [such as a signal wire touching the box or other ground conductor].
  Introducing power supply adds more user requirements, to which I like to add: test for non-shorting conditions at battery clip +/- [and/or PS jack] prior to applying power supply...following through into the circuit...the power supply may have diodes [which are one-way current 'switches'], and DC blocking or filtering capacitors [which require understanding the difference between DC and AC before knowing what to expect when they're in a circuit].
   And last but not least, resistors which resist AC or DC.
    Finding a block is easiest when something changes if it is lifted, this can't happen with more than one block, breaking the circuit down into segments allows an unblock condition change to be noticed, a noticed unblock is a debuggers cause for celebration.
  Having the circuit on a testjig is good, that signal input and output can be tested for [so that the input of the circuit actually goes to the guitar cable tip etc., gnd.s are all made and the through-wiring can be verified as 'works'...then the actual circuit board can be tested on, all blockings having been sorted as throughways for the signal...then Gnd. is Gnd.d, the circuit input/output could be spliced right into the guitar cable [power the circuit with a battery, no DC gets through the capacitors], but is easier to test on a testjig which connects the Gnd., input and output only...directly through jacks/cables [test all that stuff, all the way from guitar cable tip through amp cable tip...if the in/out wires are twisted together the guitar cable tip and amp cable tip should be a connection...getting rid of all the switch confusion makes it easier to test the circuit, getting rid of the circuit makes it easier to test the bypass switch/etc. wiring.

[markbee]

twabelljr: i checked the continuity from imput tip through yellow one > red jumper > other yellow one the output jack ant it is all good, I cant find any other mistake than the opamp which cant be causing the no singnal coming through thing. im just confused

[twabelljr]

i checked the continuity from imput tip through yellow one > red jumper > other yellow one the output jack ant it is all good

If that is all good you should have signal in bypass. Did you test it with cables plugged in and check tip to tip or just touch the jack lugs? Make sure the input is not shorted ground also. The test you did you will show continuity even if it is shorted to ground. If your signal circuit tests good like you say and you do not have bypass there almost has to be a short in the signal circuit. From your symptoms and what I can tell from the pictures I am thinking the yellow wire on the input jack is connecting to the ring/sleeve with a cable plugged in which is the power supply ground. (like the single red wire and yellow wire need to be switched at the input jack) I can see both jack sleeves connected together so that is ok. Sorry if I am way off and good luck!  

[Cymbaline]

I had the same exact problem just this last week, when I built the BSIAB2 (Brown Sound In A Box 2) from GGG.  The effect was dead, and I couldn't even get the bypass to work.  It turns out the input was shorted to ground; I guess it was shorting against the case or something.  What fixed it was to disassemble the pedal, taking all the guts out of the enclosure, board, jacks, switch, pots and all, and then it worked perfectly.  (Be very careful when you do this so as not to break any wires.)  I'm still not sure what was shorting against what exactly, but I was very careful when I reassembled it to make sure the connections on the input and output jacks weren't touching anything, and now it works just fine.

I'd give that a try.  As posters before have said, since the IC is soldered in backwards the effect won't work, but you should be able to get the bypass function to work if everything's soldered together right.  You should be able to get all the guts out in one piece (so to speak), but you'll have to unsolder the wires to the DC input jack, because of the way it's mounted.

By the way, I've been lurking a while but this is my first post.  Hi everybody!