Skip to content

July 5, 2017

Gibson Robot Guitar – Revisited

I was in the studio the other day, went to tune up the Gibson Robot and…meh. Nothing. Plugged in the charger, and couple hours later. Nothing.

Swell. Just swell.

Back in 2014 I’d fixed it with a couple of El Cheapo rechargeable batteries I sourced off eBay. Fast forward three years and those batteries were toasted.

Of course this is pretty much standard for NiMH so…no big surprise. And those 2000 to 3000ma rated batteries off eBay, keep in mind those are just NUMBERS. For example I charged up some Eneloop’s, got 1.48V full charged. Did the same with some A3300 batteries (and some unmarked ones) off eBay and the best I got as 1.37V. Maybe you’re thinking 1/10th of a volt isn’t much, but trust me, in this case with a robot, it’s huge (for other reasons).

As it happened someone emailed me within the last week about that original blog post and since I had some time I decided to dive back into the Tronical murky waters.

The Examination

Instead of grabbing another set of junk batteries I decided that I needed to adjust my thinking for “long term”. If the batteries were going to be replaced every three years I might as well make it easier to do.

Next I didn’t want to use cheap batteries. My choice was to go with the Sanyo or Panasonic Eneloop batteries. The problem here is that the batteries don’t have solder tabs on them so one has to solder right on the battery terminal.

I started by looking for a dual AA battery holder than would fit in the confined area of the Gibson. I found a couple of these in my parts bin.

Bholdaa

The one I had fit, the second one was wider than the Gibson cut out so no go with it. I soldered up the wires, plugged it in and was rewarded with a flashing sequence of blue LED’s around the MCK ring. I have NO idea what that indicated. But there’s no way the thing would respond or tune. Cool flashy LED’s though….

In trying to figure out why, I originally thought the electronics might have fried itself, I came across the specs for these holders. Specifically 1 AMP output MAX! Any more than that the contacts/wire can heat up. Even with the connection I did have there was a large voltage drop. Mostly they want FAR less than 1 amp to be happy.

Last time I tried to power the Gibson with a bench power supply, it failed miserably. Apparently my new bench supply is of higher quality and it powered up the robot just fine. My goal was to measure the current used at idle and when tuning.

At idle the robot used around 340ma (one third of an amp). That surprised me, I didn’t think it would be that demanding.

Kicking the robot into tune mode, wow. Anywhere from 800ma to 1.6 Amps. Depending on how many tuners were running.

No wonder the batteries were soldered in.

The Options

I could either replace the batteries with some new soldered ones or find a battery holder that would fit.

According to what I could find, Eneloop does make tabbed batteries but I could find no source in North America for them. And really, I wanted to avoid soldering in new batteries if I could.

Which lead me to decide on a battery holder.

Armed with some electrical data, I started looking for “spring less” battery holders. Springless holders typically have large metal tabs that rub against the ends of the battery. The current through these connections can be far higher than the typical brass button and spring units in the previous photo.

Try as I might, all the holders I found weren’t going to fit into the Gibson’s battery area.

So you think that would be the end of it right? Nah.

Unleash the Maker

Back in 2014 I didn’t have a 3D printer. I do now. Couple of them as a matter of fact. I used Tinkercad and started designing a box that would fit in the area. A tray is what I finally found worked best.

But first, I needed some UBER springy metal to make battery tabs with. Off I went to eBay, Banggood, etc and found a few things, but not what I thought I could use. So I started to look around the shop for springy tin and presto. It darned near jumped out at me…

Jacks

When I was building guitar stomp box pedals, I was using a lot of these jacks on the PCB for connections. Nice springy tin connections. Yep. I cut the plastic off two of them to get four terminals. Bent them so they’d hold a battery.

Then it was off to add in the design to hold these. So the first couple of designs didn’t work but eventually I got a design that was going to work, at least good enough to test with.

IMG 1195

I couldn’t solder the wires on the tabs when they were in the battery housing I’d made or the PLA would melt. I decided to put the wiring on the bottom of the holder. Didn’t really matter any way.

IMG 1196

I used two terminals with a 16 gauge jumper wire. Took some wrangling to get it in but I got it.

IMG 1197

From the battery side it looks like this:

IMG 1198

Oddly enough, there is a LOT of tension in those little spring clips. So once the batteries are inserted you can see the force of them pressing against the ends.

IMG 1199

I finally put the whole thing back in the Gibson and it works absolutely perfect. As good as or better than the original Tronical design. When I plugged in the charger, it sync’d right up with the guitar and quickly charged the batteries to full.

IMG 1200

Summary

Is this perfect? Will it stand up? I don’t know.

I do know the batteries are wedged in the holder pretty darn good BUT, if they do come loose, I’ll put a zip tie around them and the holder so there’s no way they can budge.

Looking at the clips, I can also see another way to do this. A couple of M3 screws, some terminals, no spring clips needed. But then again, this might not work as good as the spring terminals…

All I know is that when the batteries go again in three years, I’ll be putting in another set of Panasonic Eneloop’s and it’s going to take me about two minutes to do it.

Read more from 3D, DIY, Guitar

Comments are closed.