First time pedal build issues

Discussion in 'Burnt Fingers DIY Effects' started by anthrotony, Apr 11, 2019.

  1. anthrotony

    anthrotony Tele-Meister

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    Hi everyone, first a disclaimer of sorts. I was trained in electronics decades ago but my career took a different direction away from soldering irons. I still have a decent technical understanding though. However, I have a neurological disorder which is annoying when playing guitar as my hands are not very steady - this makes soldering a little more challenging on something as small as this pcb! But I went slowly and steadily checking all the joints as best as I could.

    So that out of the way. I have just built a FuzzDog Ross compressor and have several different (I think) issues. But I'd like to start with the first one which is making me pull my hair out. And I don't have so much to start with.

    I decided to test using FuzzDog's recommended method.

    Screenshot 2019-04-11 at 12.41.33.png

    So, testing my new battery it now reads 7.9 VDC (it was just over 9V at the beginning). The battery got hot, so I checked for obvious short circuits and didn't find anything except that somehow my live voltage wire to the board was loose so I fixed the solder joint. A continuity check between the V and G joints is good. There's no short circuit at this point. But when I measure the voltage between V and G on it reads 0.9VDC...

    Before I continue checking my board, I'd appreciate suggestions as to how I can lose 90% of my voltage at the entry point on the pcb. Does this still reflect a ground drop somewhere else on the board?

    Thanks!
     
  2. Splodgeness

    Splodgeness TDPRI Member

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  3. anthrotony

    anthrotony Tele-Meister

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    Oh thanks for doing that -- I should have thought to post the link for the schematic. I will make some time to look at those this afternoon and report back.
     
  4. anthrotony

    anthrotony Tele-Meister

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    @Splodgeness I've checked the polarity for each of C9 and D1 and through the magnifying glass they seem correct. I installed the caps using FuzzDog's guidance that the longer pin was positive (into a square pad on the pcb). A physical inspection of all the caps reveals that the vertical stripe, negative, is in the proper hole. And D1 has a cathode stripe over the negative pad (square) as expected.
     
  5. lastRebel

    lastRebel Tele-Meister

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    Is your battery snap using colored wires? If it were wired backwards, I’d think D1 would let full battery current go straight to ground. ?
     
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  6. anthrotony

    anthrotony Tele-Meister

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    I would not have thought about that... so I checked and yes it's ok. Thanks.

    Still looking for ideas. I'm still looking to see if I can see any particular cold joints or solder bridges as well.

    For sure, the circuit drains the battery very quickly, so I'm not even sure where else I could actually check voltages. So I'm very much still looking for suggestions :)
     
  7. Splodgeness

    Splodgeness TDPRI Member

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    Can you post up some photos? Component side and track side of the PCB?
     
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  8. ICTRock

    ICTRock Tele-Afflicted

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    you started where I would have started, visual inspection

    I always suggest continuity testing and tracing next ... does each part go to the next or to all the places it connects? do the pins that are supposed to go to ground get there? is the stuff that isn't supposed to be going to ground end up there?

    if continuity and tracing doesn't get it done, time for voltage checking ... is the voltage where it should be?

    finally, a looper pedal, function generator(or atari punk console), or someone playing the guitar and an audio probe will guide you through the circuit to where the signal dies.
     
    Last edited: Apr 12, 2019
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  9. anthrotony

    anthrotony Tele-Meister

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    I'll get some pretty sharp photos and post asap, probably later today.

    @ICTRock Yes, I'm trying to recall my process from so long ago. But I don't find it so logical on such a small pcb -- tracking each component to the next in the schematic seems a challenge when it's not easy to identify each component other than visual checks. The traces are mostly invisible of course. And one other thing I'm not very clear on is that there are markings on the lower side which also look like traces but I'm not actually clear about this :( My 60-yr-old brain thinks it's still very young but sometimes doesn't demonstrate it ;) In any event, the images that I take will be useful even to me as I can see them blown up to the size of my laptop screen to help with circuit tracing. I will be building an audio probe in the next day or so in the hope that I get to the point where current is actually travelling around the circuit rather than, as I suspect, going straight to ground. I found that my 9v battery is now only reading 7.5v after perhaps 15 minutes of connection, so that's still my best guess.
     
  10. anthrotony

    anthrotony Tele-Meister

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    Well I got some photos which show the naked truth of my soldering joints :( The first thing I should explain is the jumper wire under the board. My initial iron was too hot and it massacred the pad under R13, causing some of the trace to come away from the board. This trace would have gone towards the top left of the board (component side) and then went horizontally right under those caps, ultimately joining C16. Rather than try to stick the trace back to the board I decided it would be safer to run the jumper wire. I measure 10Kohms between the two connections so that appears correct, although I suppose it is possible that I've messed up something else at either end of the jumper, or even causing a short to ground at some point - but I thought that the correct resistance measurement does not support that idea.

    My photos show some solder splashes and some joints that look a little dark/dull.

    It is very difficult to see the D1 in the lower left quadrant, mounted vertically.

    Anyway, I hope this might help shed some light on the problem.
    Cheers,
    Tony pcb2.JPG pcb19.JPG pcb7.JPG pcb10.JPG pcb17.JPG
     
  11. Splodgeness

    Splodgeness TDPRI Member

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    Having looked at your photos and compared them with the layout diagram I think you have your +9v and Ground connections reversed on the PCB. It looks like the orange wire connects to the red wire (ie the positive 9V) from the battery clip via the connector block and you have soldered this to the "G" pad on the PCB. The green wire on the PCB "V" pad is connected to multiple green wires in the connector block and what appears to be the black wire from the battery clip (ie the negative 9V).

    Connected this way, D1 will act almost as a short circuit (It's doing what it is there for in the circuit, to protect against a reversed power supply connection).
     
    Last edited: Apr 13, 2019
  12. anthrotony

    anthrotony Tele-Meister

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    Looking at my own photos, I think you might be right. There were no markings on my pcb (seller error) except the LED, which is the empty pad. So if the image of an older board on the pdf is correct, then the order of the pads from left to right would be IN - V - G - OUT - LED. From the underside of my board in the last photo above, it indeed looks like I've soldered IN (white) - G (green) - V (red) - OUT (black) and of course LED left empty as this actually get on a separate daughter board. I'm going to look at my pcb as soon as I'm able, and initially simply use my connecter blocks to reverse these two wires and check. Thanks so much for taking the time to look at this on my behalf.

    Cheers,
    Tony
     
  13. Splodgeness

    Splodgeness TDPRI Member

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    No problem! Hope you get it working
     
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  14. anthrotony

    anthrotony Tele-Meister

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    Well, a quick message to FuzzDog to confirm that the correct pad order was indeed the same on the new unmarked pcb was confirmed, so I switched temporarily the red and green wires from the board (so red was now ground) and then rechecked voltages. Correct at battery, correct at board entry points, and just for my own concerns, correct at pin 6 on the IC (ground) and pin 11 (V+). So I'm going to attempt a test to see how the board functions...

    I'm suitably embarrassed that despite multiple visual checks, I didn't see the wiring crossover. Pretty ticked off at myself about that. hopefully lesson learned. As soon as I can power up my amp I'll try this out and report back. Many thanks so far to all who have contributed :)
     
  15. anthrotony

    anthrotony Tele-Meister

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    So I just managed five minutes to plug a guitar through the pedal, and I'm not at all surprised, but there's something else going on. No signal being output, no noise whatsoever. So I'm going to make some time later today to start debugging again... Should I post back to this thread as a continuation, or is it better "protocol" to start a new thread? Just in case anyone has an idea on this one!

    Cheers,
    Tony
     
  16. lastRebel

    lastRebel Tele-Meister

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    I think you would be ok continuing in this thread. Glad you got that sorted out! Good start...
     
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  17. lastRebel

    lastRebel Tele-Meister

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    I’d start with checking all 3 diodes for proper operation. D1 may have overheated dumping that much current to ground. These are picky about getting too hot, even with soldering.
     
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  18. jimilee

    jimilee Tele-Holic Silver Supporter

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    I did the same thing one time. Best bet is to make an audio probe and start at the beginning.


    Sent from my iPhone using Tapatalk
     
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  19. anthrotony

    anthrotony Tele-Meister

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    Hi guys, I'm trying to make the time to continue my circuit testing while taking care of a couple of injured kittens. That's almost a full-time job, lol!

    General question as I'm reading contradictory advice on the web... I'd like to measure the three diodes, especially the main D1. I thought that I could disconnect power (easy as I'm using the battery harness) and measure either resistance through the diode in both directions while it is still on the board, or use the diode setting on my DMM the same way, but I've read several times that the diode has to be partially lifted from the board for this to be accurate. Can anyone help me understand which method is correct please? I figured it would be good to know if they are functioning correctly before getting into serious diagnostics :)

    As soon as I can make the time I'll build an audio probe. I think I have a couple of spare capacitors around that I can use with an old guitar cable...
     
  20. jimilee

    jimilee Tele-Holic Silver Supporter

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    It has to be lifted, at least on one end. If you don’t, you’re measuring the circuit resistance. Resistors and caps are the same way.


    Sent from my iPhone using Tapatalk
     
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