Author Topic: HEADTRIP Voltages  (Read 454 times)

zgrav

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HEADTRIP Voltages
« on: February 15, 2019, 01:28:55 PM »

I have assembled the Headtrip and encountered some difficulty.  Wiring and parts look OK after checking with DMM for continuity, and all voltages on the FV-1 are correct with the exception of pin 5.  According to the build doc, pin 5 should be at 3.2v.   It is soldered to the board, but according to the circuit diagram the board for that pin does not connect to anything.   On the FV-1 datasheet the pin is described as  "clip" with the explanation that it is for "clip LED output" (probably a clipping signal for an input that is too hot).  My voltage reading on that pin is in the low mV with no signal going in.  Should it really be registering 3.2v?

As for the effect, I get a clean dry signal, and some wet signal that is altered by the three pots.  But in addition to that I get a lot of weird variable high frequencies that sound like someone tuning a short wave radio.  Those sci-fi noises drown out the audio signal.   I still need to trace the audio signal with a probe to make sure a clean signal is going in to the FV-1, but I'm also thinking I might have gotten a bad FV-1 chip.  This was a purchase from an ali-baba seller so I won't be surprised if that turns out to be the case. 

madbean

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Re: HEADTRIP Voltages
« Reply #1 on: February 15, 2019, 01:44:41 PM »
You can dis-regard the voltage reading on pin5. Like you said - it isn't connected to anything and has no effect on the operation of the circuit.

The other problem is much more concerning. Are you sure you have the correct type of crystal in there?
I own madbeanpedals (duh). I am part owner of Function F(X).

zgrav

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Re: HEADTRIP Voltages
« Reply #2 on: February 15, 2019, 05:48:07 PM »
I at least ordered the right crystal for the board.  : ^ )     I have spares sourced from other suppliers, so I can swap the crystal out and see if it makes a difference. 

zgrav

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Re: HEADTRIP Voltages
« Reply #3 on: February 15, 2019, 05:49:10 PM »
Did not have this problem with the Dreamtime project, but the FV-1 for it came from Smallbear.

zgrav

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Re: HEADTRIP Voltages
« Reply #4 on: February 17, 2019, 12:34:53 PM »
Everything on the Headtrip PCB tests OK for voltages on all IC pins, continuity and part values.  Dry signal OK.  Audio is going into the FV-1 on pins 1 and 2  Only noises like a theremin on pin 28, and then only when the external patch toggle is selected.  Probably would be good if I needed some sci-fi effects, since those noises can be adjusted for delays, repeats, phasing with pots 1,2,3 for the respective programs.  But not what I wanted for this pedal. Nothing but silence on pin 28 when the internal patches are selected.   Seems like a bad FV-1 chip to me, but other thoughts are welcome.   I think I will order a replacement chip and give it another try.  I plan to wick as much solder as I can off the FV-1 pins.  After that, would it be better to use a heat gun to free the chip from the board, or try to do several pins at a time with my soldering iron?   

DLW

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Re: HEADTRIP Voltages
« Reply #5 on: February 17, 2019, 12:40:17 PM »

zgrav

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Re: HEADTRIP Voltages
« Reply #6 on: February 17, 2019, 02:04:46 PM »
thanks for that link.    I was not familiar with that product.

zgrav

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Re: HEADTRIP Voltages
« Reply #7 on: February 24, 2019, 08:28:02 PM »
Just wanted to say thanks again for the link to the low-temp solder.  Worked great to let me remove the FV1 chip without damaging the board.

zgrav

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Re: HEADTRIP Voltages
« Reply #8 on: March 03, 2019, 09:46:56 PM »
final update -- replaced the fv-1 chip and the effect works great now.  so overall a PITA to have that part be the bad one, but overall a self-contained class in troubleshooting everything else first.   the effects are great and it is a fun pedal to just get lost in picking out different things on the guitar.

madbean

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Re: HEADTRIP Voltages
« Reply #9 on: March 03, 2019, 09:48:38 PM »
I'm glad you got it sorted. When I started getting serious about the FV-1 stuff I bought a $50 SMD heat gun. I'm super glad I did because it saved my bacon a few times. Being able to remove FV-1 chips reliably pays for itself after you do it 2 or 3 times.
I own madbeanpedals (duh). I am part owner of Function F(X).