CA Guitar Repair Blog: Caravan Music HS4140N

Overview

It's been a long and winding road getting this Caravan Music HS4140N "trans-acoustic" back into gig-worthy shape. After all, the owner's a well-known busker, and had always intended on using this guitar live. Two issues put paid to his intentions, though. The first was high action, and the second, a malfunctioning preamp.

Lowering the action was rather straightforward, as the truss rod was working and there was no belly bulge or lifting bridge. We only had to dress the frets and condition the fretboard, besides replacing two bridge pins. And to further enhance playability, our strings of choice were D'Addario EZ890 (9-45).

Ah, the malfunctioning preamp. This was a different kettle of fish altogether, more precisely, a "Sevillana Digital Module Trans System A-3," or "A-3" for short. As with most onboard chip-based technology, system failure is always lurking in the shadows. In the case of this preamp, recharging the battery became a major headache, and even when there was enough juice to power up, output was intermittent. We ended up disconnecting the A-3 and installing an under-saddle piezo element soldered directly to the endpin jack.

Sevillana Digital Module Trans System A-3

Although the A-3 is no longer in this guitar, we're including this section for educational purposes. According to the literature, the A-3 is a trans-acoustic guitar pre-amp and digital effects module system "that adds digital effects directly through the guitar body without needing an external amplifier." Its four main components are an under-saddle piezo pickup, an onboard digital processor module, a rechargeable battery, and a "Transducer Actuator," which is "an internal speaker/actuator attached to the back of the guitar body to vibrate the wood and create acoustic effects naturally."

A-3 Control Panel

A-3 Preamp Module Housing

A-3 Rechargeable Battery

A-3 Under-Saddle Piezo Pickup

A-3 Transducer Actuator

A-3 Endpin Jack Assembly

Close-Up of A-3 Endpin Jack

Fretwork

Fret leveling involved successively finer grits of abrasives on sanding beams, as well as diamond sharpening stones. Following this was fret crowning with a StewMac Z-File Fret Crowning File (5080). The sides of each fret were then polished with successively finer grits of silicon carbide paper wrapped around a decommissioned ATM card.

Fret Leveling - First Pass

After the First Pass

After the Final Pass

Frets Are Level

StewMac 5080 Z-File

Fret Crowning Completed

Polishing the Sides

As for the fret tops, they were first abraded with silicon carbide paper from 400 - 1.5K grit, and then polished using 3M Scotch-Brite Pads and 0000 steel wool. All this left fine wood and metal particulates on the fretboard, which were cleaned off with naphtha. Finally, the fretboard and bridge were conditioned with lemon oil.

Abrading the Frets

Polishing - 3M Scotch-Brite Pads

Polishing - 0000 Steel Wool

Cleaning the Fretboard

Conditioning the Fretboard

Conditioning the Bridge

The Home Stretch

First on the list was plastic hardware. The saddle and bridge were fine after a little cleaning, but two bridge pins needed replacement. One was so brittle that it broke in two on our first attempt to dislodge it with a bridge pin puller. As for the second, it was black, and replaced purely for aesthetic reasons.

Existing Bridge Pins, Saddle and Nut

As mentioned in the Overview, the entire Sevillana Digital Module Trans System A-3 was dismantled and disconnected, save for the module housing/control panel. This housing was retained because removing it would have left an unsightly hole in the upper side-bout. We then cut off the mini mono jack from a new under-saddle piezo element ribbon, soldered the cut end to a new endpin jack, and installed the assembly. It was then simply a matter of installing D'Addario EZ890s, stretching the strings, and tuning to pitch. The owner dropped by this afternoon to try out his HS4140N, plugged straight into a Fender Rumble 15. Click HERE to watch the video.