1973-75 Gibson Howard Roberts.
Here is an early 70's Gibson Howard Roberts guitar that came through my shop recently. Let me start by saying how much I love Howard Roberts. Never heard of him? He was a mean west coast session player with a very tasteful style. I recommend you check out his 1963 quartet double album "Color Him Funky: H.R. is a Dirty Guitar Player". Really slick three minute funky jazz tunes.
Howard Roberts is tough to find on YouTube, but here's a tune off of "Color Him Funky".
Get ready for the organ intro.
I had the pleasure of working on another one of these guitars a few years ago that I fell in love with. The guitar was later put up for sale and I only wish that I could have grabbed it. Ah, the ones that got away...
This most recent Howard Roberts that came through the shop is a red single pickup model with a serial number that dates it to 1973 - 1975. The controls are a master volume, mids / bass tone control (or "choke") and a standard tone control. There was also a two pickup model available as well.
Oval sound hole with a single floating humbucker.
Controls top to bottom: master volume, mids / bass tone, standard tone.
“Howard Roberts” tailpiece.
This is a player’s guitar.
The owner of this guitar is Tom Pendergast and he plays a lot of gigs around Boston. I met him at Johnny D's in Somerville, MA where he regularly plays their weekend jazz brunches. (I always get the catfish and eggs). Tom brought this guitar to me because he was having troubles with the pickup's signal randomly fading. The volume would never cut out, but would be significantly quieter at times. Very odd. I have dealt with many connection issues that would cause a guitar signal to cut in and out intermittently (a loose output jack for example), but never a temporary drop in volume. A secondary concern of Tom was that this guitar's middle tone control did not work. This additional tone control is unique to this guitar and is designed to only roll off the mids and bass frequencies. I was given the green light to fix it since I had to troubleshoot the entire wiring harness anyway.
So, the plan of attack:
1. Remove the strings and bridge, and secure the tailpiece.
2. Remove the control knobs and nuts to allow the wiring harness to be pulled out through the sound hole.
3. Clean all three control potentiometers ("pots") and other connections.
4. Touch up any poor solder joints, bad connections, etc.
5. Troubleshoot the mids / bass tone control.
6. Test and reinstall the wiring harness.
7. Clean, restring and setup
: : : : : :
Here we go ...
Handy tool for safely removing stubborn knobs.
Knobs tagged so they go back on the same pots they were removed from.
Circuit components removed. Note the RCA connection that connects the pickup to the rest of the circuit. Another wire (not pictured) runs to the tailpiece that grounds the strings and prevents complete removal of the wiring harness from the body.
Contact cleaner is used to improve these old corroded connections. Hollowbody guitars tend to have “dirtier” controls as they are not sealed inside a control cavity like a solidbody guitar. I had a theory that this RCA connection was corroded and a possible cause of the volume drops. The pots were all cleaned as well as the output jack.
Mids / bass tone control (left) has a component missing that mounts to the bracket. The schematic shows an inductor or “choke” that sets the frequency range of this control. This mids / bass control is completely disconnected from the circuit’s signal path.
The original 1.5 H inductor is very difficult to find, so I used three 0.5 H inductors in series. (Shout out to Bob Dettorre over at DST Engineering for sourcing these for me.)
Test rig before soldering in the new choke. I temporarily connected everything and tapped on the pickup with a screwdriver as I turned the mids / bass tone control and I listened through the amp. I even went as far as to string the guitar up to see how it was working.
Here are the three inductors wrapped in shrink wrap to help protect the delicate coil wires.
The three inductors are wrapped together with electrical tape to form one big inductor module. Then they are further secured with zip ties.
Here is the inductor “choke” secured to the potentiometer. Convieniently it had a bracket I could mount to with a zip tie, bolt, lock washer and nut.
Another view of the new mid / bass “choke” control, not wired up.
Here is the cleaned, repaired and tested wire harness ready to reinstall into the body. Note in this photo you can see the green ground wire that runs to the tailpiece.
A closer look at the mids / bass tone (left) and the standard tone (right).
Electronics reinstalled and the guitar sounds great. The mids / bass tone control is a very cool feature that you do not find on most guitars.
Only time will tell if cleaning the components along with touching up poor solder joints has corrected the volume issues. I could have just replaced the entire wiring harness with new components, but felt that would be overkill on this vintage guitar. As for the inductor on the second tone control? That sure was a curve ball I didn't see coming. Luckily my amp guy Bob Dettorre found an alternative solution to a difficult-to-find original Gibson part number. The real trick was figuring a good way to secure those three inductors (in series) inside the guitar. The bracket on the pot was a lifesaver and using a proper zip tie to bolt to that bracket made the module very secure.
Overall this was a fun and challenging project that helped push my boundaries. Speaking of boundaries, I am reminded of a great quote. It inspires me so much that I even have it up hanging on the wall.
Hopefully it will inspire you.
"It is understandably human to want to sound good to ourselves when we practice, and therefor play what we already know well. However, real advancement comes from tackling new things; coming to grips with work that is more advanced, work that is out of reach unless one really tries to accomplish the seemingly impossible - after all, they're only impossible for a while."
-George Van Eps, Harmonic Mechanisms for Guitar, Vol. 1
1973-75 Gibson Howard Roberts.