digitech - Unbroken String

TC Helicon VoiceLive3 Pedal Refurbishment

December 23, 2018December 9, 2018 by latchaw

A lot of capable technology lives in this device. However, if the musician can’t select a configuration because the big rotary selector knob broke off, then it’s e-waste. Can the Unbrokenstring Crew bring this pedal back from the dumpster?

Pedals live on the floor, and there is plenty of dust to attest to to the fact that this unit has been working hard exactly where it was born to be. No harm in cleaning and detailing this unit before we’re through!

The main issue here is the broken rotary encoder. We have the knob, but not the shaft.

Time for a quick tour before we begin. This pedal serves both vocal and instrument duties. Flexible monitoring options are available, as well as 3.5mm stereo headphones out and line-in capability.

Separate paths are maintained through the unit for vocal and instrument signals. Stereo effects are available.

Midi, USB in and out, and a power switch complete the rear panel. That black rectangle above the USB ports is a cleat to tie off the power cord, to make it a little more difficult to pull the barrel plug out of the power jack.

It takes a lot to get into this box. Let’s start at the bottom.

The bottom lid is off. So far, so good.

The footswitches are VERY old school, rugged American made switches, proven reliable since the middle of the century.

Let’s remove the sides next. This bracket on the side panel supports the bottom circuit board.

These are the external screws on the sides.

These are Torx-head cap screws, giving the device a cachet of ‘tamper-proof-ness’ unless you have the right tools.

Next, the rear panel comes off. More Torx screws.

Under the side plates, metal plates support the unit to make a very strong metal box surrounding everything.

At last, we can get to the next layer. The unit is still upside down.

I’m documenting where cables go. This is a front-panel indicator assembly.

More cable documentation. See the Ruffles potato chip?

Most of these cables will be marked with a Magic Marker to identify them for reassembly.

Next, the front panel is removed. These knobs pull off.

There are no lock nuts under these controls. Interesting…

We have a few more screws to keep track of. Many of these are a certain length, and shall be returned to the right place.

The LCD is tilted back to gain access to a few more Torx cap screws. Our final objective is in sight!

The broken rotary encoder is on the same circuit board as the LCD. To minimize stress on the circuit board, the old rotary switch is cut away, leaving the individual leads in place. These individual leads are much easier to de-solder.

The holes where the new encoder goes are cleaned and ready to go.

This rotary encoder is a special order part. Not just any component will fit.

This is a workmanship check of the solder-side of the rotary encoder.

And here is the component side. Again, not just any part will work here.

We can take a break and do the clean-up prior to reassembly. Compare this with the first picture. Yes, the LCD window has been cleaned and polished.

Reassembly is the reverse of assembly (wow, that’s profound.) The correct fasteners must be reinstalled at each step.

Everything is back where it belongs. Remember the Ruffles potato chip? That is actually a dab of adhesive that secures the flat ribbon cable. A dab of silicone will be added in a moment to secure the ribbon cable again to the same spot.

Looking good! Everything initialized. The factory reset procedure is complete.

Somehow, I thought that this was an appropriate preset screen to display. I think we’re done!

Here is a video showing how the rotary encoder works to change presets and configure the unit into different operating modes.

Support this band! – Fake Believe

Thanks for reading all the way to the end!

CONTACT – David Latchaw EE
281-636-8626

Digitech GSP1101 Effects Processor Repair

February 3, 2017 by latchaw

A frantic spouse called to explain that she was vacuuming and hit this ‘thing’ and broke this little piece off it. Could I fix it before her husband found out? The Unbrokenstring Crew to the rescue again!

The gain knob on this unit is a rotary encoder. This component is available from several vendors.

She kept the knob, which is GREAT news, because although the rotary encoder is available, the knob is not.

The remains of the shaft of the rotary encoder was removed from the knob. So far, so good.

Let’s get to work replacing the broken rotary encoder.

As is the usual case, all the knobs come off first.

The circuit board lifts away easily.

These cool little plastic spacers set the geometry of the rest of the buttons and controls.

We will put this piece away somewhere safe while work elsewhere continues.

To minimize the stress on the circuit board while removing the old component, the body of the broken rotary encoder is cut away from the component leads at an angle perpendicular to the circuit board.

With the component cut away from the circuit board, de-soldering the legs becomes trivial.

The component legs are gone. This is a high-quality circuit board, double-sided copper and plated-thru holes.

Both sides of the circuit board are cleaned up.

Here is the new part, ready to be soldered onto the circuit board.

We are ready for reassembly. That plastic spacer is re-installed as it was before.

The cable carries all the signals back and forth to the front panel. I like this bit of orgami.

The circuit board is held in place by the bodies of the controls, which are in turn bolted to the front panel.

Everything is back together, ready for testing.

This looks good! While we were at it, we will do a factory reset.

Now, everything is as it once was. And the husband was scolded for leaving his toys on the floor, where she could hit them with the vacuum. Maybe I could sell him a rack case?

Thanks for reading all the way through!

CONTACT – David Latchaw EE
281-636-8626

DigiTech Whammy Pedal Checkout

November 18, 2016 by latchaw

This pedal wouldn’t work regardless of how it was connected. He tried the supplied power supply and a pedal power unit in his pedal board, with no luck. Could the Unbrokenstring Crew straighten out this mess?

We put the pedal and the power unit (wall wart) on the bench and verified that nothing worked.

Here is the clue. The customer provided a DC 9v output wall wart, a power standard which is commonly used in the world of guitar effects pedals. That power standard is not compatible with this unit.

Not much else to see around the rest of the pedal. The MIDI control is a nice touch.

This is the ‘correct’ wall wart. This one says 9vac output, which is what this pedal needs. I love eBay!

Something is rattling inside this unit. Removing these Allen head cap screws will allow us to open the case.

This is what is rattling.

And here is where it goes. This hardware works well, so we can set the switch aside for now.

The electrical connection between the circuit board ground and the chassis is made via this metal stand-off. This connection was intermittent until we took the wire brush to the end of the stand-off.

The light spot on this circuit board is called ‘measling.’ This indicates that something got very hot.

This inductor goes between the power supply and the chassis ground of something plugged into the pedal. So, it failed. The head of the destruction caused the measling seen above.

Here is another view. This inductor serves as a simple noise filter when nothing is plugged into the guitar input jack.

The inductor is replaced and the unit goes back together. Working with the correct wall wart, this pedal is fun! It does pitch bending and chorus effects surprisingly well, considering its age and the technology used.

Thanks for reading all the way through!

CONTACT – David Latchaw EE
281-636-8626