Home Forums GuitarPCB Build Support EMEXAR 3 Micro Amp No Sound in effect mode.

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  • #19025
    Handsom .
    Participant

    Hello I’m having trouble with my build. I am getting sound in bypass mode, but no sound in effects mode. On thing that may be causing the trouble is I replaced C5-15uf with a 22uf as I was not able to find a 15uf capacitor with the voltage I would like unless I was going to buy 500. Lol. I will upload images shortly. If someone can confirm the Orientation of the pots also that would be great. This layout is just giving me trouble…. I went with the 10k resistor and jumper cable for the volume but I have my doubts if it’s correct.

    #19027
    wilkie1
    Moderator

    Install pots with the #1 lug soldered to the pad marked with a small “1”.

    Please provide good photos showing front and rear of the board as well as views of all wiring, jacks and switches.  We are unable to help further without these.

    #19030
    Handsom .
    Participant

    #19031
    Handsom .
    Participant

    So it is set up with the input on the left and output on the right but the shouldn’t matter as long as I insert the jacks accordingly…

    #19033
    Handsom .
    Participant

    I chose to use a Tl072 and here are the readings:

    pin1:0   pin2:.09   pin3:0   pin4:0   pin5:0   pin6:0   pin7:.06   pin8: 0

    I also don’t know if the 4001 is in the tight way. I am getting only getting a reading at the stop of 8.63

    #19034
    Handsom .
    Participant

    Also what is the unmarked pad above c5 for?

    #19039
    Barry
    Keymaster

    Sorry for butting in but I figured you may need this info asap. (late at night) Looks like a Micro Amp Build.

    So you cannot use a TL072 with that circuit. That is a Dual Opamp.

    You must use a TL071 or the suggested LM741 which are Mono Opamps. Always look up Datasheets before substituting. The pinouts are different and that is why you are getting no voltages.

    The extra pad above C5 is there in case you want to use a Film Cap instead of an electrolytic.

     

    I did not check anything else.

    If you still have problems after changing to a proper Mono Opamp then you will need to report voltages again.

    #19042
    Handsom .
    Participant

    No thanks for butting in…. also thank you for catching that… I have originally put a TL071 in but wanted to attempt to change it out then of course mistakenly put a TL072 in… I have a 16 hour shit today but will report back once I get home tonight!

    #19043
    Handsom .
    Participant

    Are you able to identify the orientation of of the R10-1n4001, the C5-15uf(which I replaced with a 22uf which I had on hand), the R3-10m connection to VA. It is my understanding that electrical components have a tolerance range. Capacitor in particular tend to have a tolerance of 20%, though I went with a 22uf, mathematically a 10uf should be closer to spec… I went with the 22uf because I figured it’s value at least meets the rated 15uf even at its lowest tolerance…. is this the correct thought process?

    #19057
    Handsom .
    Participant

    Alright so I went ahead and changed out the I.C. Back to the original and I get a lovely reading of….

    TL071

    pins: 1)0   2).10  3)0 4)0   5)0  6).9   7)0   8) 0

    Help!!!

     

    #19061
    wilkie1
    Moderator

    You are not getting power to the IC.  Pin 7 should be close to the supply voltage @ 9V..

    #19063
    Handsom .
    Participant

    Yeah I agree. Anything above .10 would be a start! I believe it definitely has to do with the diode. There is now way in knowing which way the 1n4001 should be facing unless you know your stuff. If you look at image number 1.1. This is how diodes usually look in a schematic drawing….    image 1.1

    Since the Emexar has multiple orientations for different builds . We place the diode in R10 is has a icon of a resistor. But if you take a look at the next image 1.2 it explains pretty well the you want the negative facing away from the power source.

     

    Sooo if we go back to the emexar circuit we can see the +9v before i.c. Pin 7. image 1.3.

    Then if we take a look back at the trace on the board we can clearly see the connection between R10 and the on-board +9v. Meaning the strip should be facing south away from the +9v. Image 1.4

     

     

     

    #19064
    Handsom .
    Participant


    I hope that all came out correctly and makes sense. Very hard to navigate on an iPhone

    #19065
    wilkie1
    Moderator

    I agree.  Turn that diode puppy around and see if that solves it.  I’m sure Barry can post a clarification to the build doc.

    #19162
    Handsom .
    Participant

    So I went ahead and turned the diode facing south away from the Emexar print and pop goes the weasel… it worked, I tested the pedal after work (at very low volume) it was 12 at night and it worked! I started to raise the volume and I was getting a very nice tone and different than my other boost build. Come the next day the pedal did not work once more. Light is still functional, but the i.c. me similar voltages and I was to tired to remember to take voltages the previous night😩

    #19163
    Handsom .
    Participant

    Do we think it’s the 22uf in replacement of the 15uf that’s causing this issue? What are the circumstances in which this can happen?

    #19279
    Handsom .
    Participant

    any ideas!!!

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