Headtrip2 - Yeah, I need help...

[DaEmbassy]

The Headtrip2 is the first effects pedal I have ever constructed. I've learned a lot, but not enough to get it to work as intended.

I've attached a couple of photos of the finished product. It's ugly, but it is what it is. 

Here's what happens when I give it 9 volts and plug in an instrument:

• The instrument signal is passed through to the output nicely. I can hear it clearly on the output
• The "dry" pot works as expected - I can turn the input signal down to zero
• The LEDs light when I turn on each of the buttons.
• But the effects don't work, despite switching through all 8 of them.
• The voltage regulator is HOT, I rested my finger on it and it burned my finger!

I got my  voltmeter out to make some measurements (I kept my black lead on the -ve lead on the power supply for all measurements):

• 9.11 volts coming in.
• On the voltage regulator, the pin closest to the edge of the board shows 8.77v.  The pin closest to the centre of the board shows 0v.  Is that right?
• And yet the voltages on IC1 look OK - instead of 4.55v I see 4.3v, instead of 9.1v I see 8.7v, and pin 11 shows zero as expected.
• Every pin on IC3 (the EEPROM) shows zero volts (or a few millivolts off zero).
• I checked every pin on IC2 (the FV-1) and they are all some small number of millivolts from zero. I don't understand why pins 6,8, 23 don't show something close to VDD.

On the face of it, I suspect my my FV-1 is dead... and I would be crushed because it was so difficult to get that chip soldered to the board and not get bridged pins (I chose to use solder paste, and I let it warm up to room temperature - BAD MOVE, when I applied the hot air gun the paste went everywhere, and I took me a long time to get rid of the solder bridges).

Before I give up - could any of you share some ideas or insight into what I can do next to rescue this?

Cheers,


MBC

[matmosphere]

Kudos to you. The head trip isn't the hardest build but it's ambitious for a first build.

I am not an expert but I'd check the values for c16 and c17 to start. It seems like if pin4 of ic is measuring low it has to be something in d10, c16, or c17.

It also looks like r23 and r13 might be making contact by the adjacent pads on the component side of the board. Can't tell from the photo for sure though.

There are others on here that are way more knowledgeable than I am, so I wouldn't throw in the towel just yet. I think it took me two or three weeks to get my first pedal working and it probably had less than ten parts on the board.

[DaEmbassy]

Thank you for your encouraging words, Mr. Matmosphere.

I checked D10 and C16 up top of the board and the solder joints look fine.  Is there some other check I can do with these components?
I checked R23 and R13 for contact, and their leads aren't actually touching (thankfully).
C16 looks fine.  I ordered all the electrolytic capacitors as a kit, not realising that they were SMD (beginner's mistake).  I just ordered some 'regular' electrolytics tonight which I will get tomorrow, and so I'll replace C16, and see if that makes a difference.

Thanks again,


MBC

[DaEmbassy]

So I pulled the 100uF SMD capacitor (C16) and replaced it with a 25V electrolytic.  This was not fun, because after removing the original capacitor, the through-holes were full of solder which I could not get out.  It took about 20 toothpicks for me to finally push a toothpick all the way through each of the solder holes.  Then I could drop in the new Capacitor.

I looked at the rear of the board and all the soldering looked fine.  When I studied the front of the board, I realised that in a whole lot of instances, the solder had not flowed through.  So I took the time to reflow every single solder joint to ensure the solder flowed through, and I also took the time to straighten the leads for most components so there was no way they might lean across and touch each other.  I learned that if I took more time in the initial soldering of components to the board, I would need to spend less time reworking them.

With that done, I re-tested the unit.  The only real change is that when I turned on the effect using the switch, the input signal was clearly amplified.  But no effect was evident.  No improvement.

Help!

[DaEmbassy]

Latest PCB pictures (for reference) ...

[matmosphere]

Recheck the voltages and post them.

I would probably go ahead and switch out all the smd caps, though I don't know if that would cause your problem. If you have another voltage regulator it might be worth trying to swap it and see what happens. It sounds like the last one probably burned up when it was really hot.

[jimilee]

To remove solder from empty holes, I use solder wick, or heat the joint and blow it out. Surprised I haven't signed most of my hair off by now.


Sent from my iPhone using Tapatalk

[Govmnt_Lacky]

Pins 21-25 of the FV-1 look suspect (solder bridges)

[DaEmbassy]

This thread needs a Coda ...

I pulled the Voltage Regulator, and tested some spares to ensure the replacement was fit for purpose.

I pulled all the SMD capacitors. Unfortunately, half of the capacitors did not come out cleanly, and left one of those tiny, tinny, SMD legs in the through-holes on the PCB.  And so I began the job of removing those holes filled with solder and SMD leg.  I tried a solder sucker, toothpicks, guitar strings, but was not able to clear the holes.  I ended up adding solder, then using solder wick, over and over again to try and clear the holes. Unfortunately, "ended up" is where the story ends, because the repeated work on through holes has lifted the mask off the board in places, and indeed lifted the copper off the holes (without solving my problem).    I have snookered myself.  I need to buy another PCB, and start again.  I am determined to get this to work, so I will work on a second PCB!

So Kids, let this be a cautionary tale.  Look more closely when ordering parts and DO NOT order SMD capacitors when you should be using plain electrolytics!

Thanks @matmosphere, and all who read and responded to my posts.

Cheers,




MBC