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Yamaha G10 Repair

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Yamaha G10 Repair

Postby BJG145 » Tue Dec 18, 2018 8:13 pm

The latest inpatient is a Yamaha G10.

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MIDI guitars have had a long and troubled history. The most famous early attempt, of course, was the 1985 SynthAxe.

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Despite the bizarre styling and $13K price tag, Allan Holdsworth demonstrated its power as an expressive instrument on albums such as Atavachron.

Yamaha's 1988 G10 found a champion in the Spanish jazz guitarist Antonio Onorato. I love this live performance of Arabesque.

https://youtu.be/rkrEWA7GigA?t=135

The G10 is unusual in several respects. It has an input for a BC1/BC2 breath controller. And it uses a "predictive" tracking system which makes it more responsive than the majority of MIDI guitars, which try and figure out which note you've played after you've played it. Yamaha patented a system whereby a special pickup constantly sends ultrasonic signals along the wires, and works out the fret position by analysing the echoes. By the time you pick the string, it already knows what fret you're on.

The G10 is connected via a proprietary 15-pin cable to a G10C module, which offers MIDI output. It was originally designed to be played through the TX802 sound module, which is basically a rackmount DX7, or the four-operator TX81Z - and in fact, the G10C includes a set of guitar-friendly patches ready to be dumped to either of these modules.

Finding a complete working system isn't that easy. I've sometimes seen them surface in Japan, or Russia, but I don't think I've ever seen a complete system offered in the UK, and the cable seems particularly difficult to come by.

However, I recently noticed someone selling the guitar on eBay in the UK, and I'd also found a module plus cable in Spain, and a BC2 in Germany. So it seemed the right moment to try and put together a working system.

I'd expected problems, so I was pleasantly surprised when I plugged it in with my go-to VST lead synth (Bob Papen's Blue), and it worked straight away.

The fun didn't last long though, as one of the strings slipped down a few notches...and it hasn't worked since.

The strings, incidentally, are pretty strange...it takes six G strings tuned to F#. Go figure. (The resulting acoustic noise, though muted, is pretty discordant, as you can imagine, so people generally wear headphones or crank up the volume.)

When you turn the thing on, the G10C gives the guitar a once-over to test the strings, and if it's not happy you can't get any further. The display will show something like: "OK OK OK OK OK NG", to indicate that a string is "No Good".

Despite a lot of tinkering around with the various adjustments at the bridge, and different strings, I could never get it to accept the top E again.

I figured that the testing phase must involve the ultrasonic pickup, since that's the only thing that's being checked all the time. (You're not even supposed to touch the strings when you turn it on.) So I took a look at that.

First you peel off the outer cover...

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...then an inner cover which damps the strings...

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...and you see the three pickups. The right one detects velocity, the middle one detects bend, and the left one is this ultrasonic device that detects the finger position.

The string shown is the faulty one, and that pickup element looks sunk a little below the others.

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I'm wondering if this is the root of the problem; whether it means the string isn't in proper contact with the piezo or something.

If you take out the screws at either end of the pickup, you can lift it out. Each of the six blocks in this pickup has a small hex screw either side. I've tried removing these, but I wasn't able to change the position of the block.

It has a circuit board screwed to the back, but I haven't tried removing it. I think it would be interesting to try taking that off and see if there's any reason why the position of that end block is different, or if there's any scope for adjusting it. If so, that seems worth a try.

The next possible experiment would be to see if it could be removed and switched for one of the other blocks, to test the theory that it is indeed that block which is at fault.

I don't like to mess with this myself as I'll probably lose one of the pieces or make things worse. :tongue: Fortunately I've discovered a broad-minded electrical repair shop a mile away that seems happy to take a break from TVs and look at the latest junk I've scooped up on eBay. So I'm gonna drop it round there tomorrow and see what they think.

There's very little documentation available online, but I've discovered the joy of patents. I found a related patent application here...

https://patentimages.storage.googleapis ... 723468.pdf

...and "Fig 17" on page 15 looks exactly like the element I'm suspecting, so it's possible it might contain some useful info...
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Re: Yamaha G10 Repair

Postby blinddrew » Tue Dec 18, 2018 10:49 pm

Following with interest. :)
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Re: Yamaha G10 Repair

Postby zenguitar » Wed Dec 19, 2018 1:31 am

Another piece of guitar MIDI gear I lusted after but couldn't afford!!

And I am also reminded of Douglas Adams on Desert Island Discs; his luxury was a left handed SynthAxe because he wanted one and they didn't make a left handed version.

Still hanging on to my old Athlon windows PC ready for when I can use it to run the Axon AX50 editor.

Andy :beamup:
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Re: Yamaha G10 Repair

Postby BJG145 » Wed Dec 19, 2018 7:02 pm

...hmm, nope - the local repair guy took one look at this and shook his head. If it had been the G10C module, that would be OK...but some weird-looking guitar, no way. He gave me the contact details of someone else to try. When I looked them up, I found they specialised in woodwind repair.

I think guitar techs are going to see it as an electronics problem, and electronics techs will see it as a guitar problem. It really needs someone who's willing to embrace either possibility; the solution might involve filing a slot to get a better contact, or diagnosing a faulty connection. I'll try the vintage synth repair places, but I'm not sure what they'll be like on digital systems and MIDI.

Returning disappointed from my trip, I decided to take the DIY approach a step further and remove the six tiny screws fastening the circuit board to the back of the pickup. It wouldn't budge though. Maybe you have to remove all twelve of the tiny hex screws either side of each block as well, but that would be tempting fate for someone of my clumsiness. As it was, I managed to "ping" off one of the string retaining screws. I heard it bounce somewhere in a corner of the room, but I doubt I'll see that again. *sigh*

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Something that puzzles me is that the ultrasonic pickup only has seven wires as far as I can see; one for each string plus ground, or whatever. I'd initially imagined that this pickup had different elements to create and monitor the ultrasonic signal on each string, but is it possible that this can be done just from a single plate, with a single connection...? Seems unlikely to me. Maybe I'll have to take a closer look at that patent. This is the pickup alright, and the date seems right too. It has to be this thing it's talking about...

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Re: Yamaha G10 Repair

Postby Wonks » Wed Dec 19, 2018 7:17 pm

I'd imagine that the ultrasonic signal is pulsed on and off, rather like radar signals. A signal is sent out and then the string sensor waits for the return signal to determine which fret is selected. A new pulse is then sent out and the process repeated. As the longest send + return time will be for an open string, then the ultrasonic pulses can be sent out at regular intervals as fast as the worst-case timing allows .

Which in theory means that only one ultrasonic transmitter is needed, provided it can transmit to all 6 strings at once, so maybe the transmitter is built into the bridge unit so that the third pickup only has to sense the return signals?

The ultrasonic system is almost certainly why all the strings are the same diameter and tuned to the same note, in order to get equal ultrasonic signal travel times.
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Re: Yamaha G10 Repair

Postby BJG145 » Wed Dec 19, 2018 7:26 pm

...oh, I see! Yep, that makes sense Wonks. Clever.
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Re: Yamaha G10 Repair

Postby BJG145 » Thu Dec 27, 2018 11:06 pm

BJG145 wrote:I decided to take the DIY approach a step further and remove the six tiny screws fastening the circuit board to the back of the pickup. It wouldn't budge though. Maybe you have to remove all twelve of the tiny hex screws either side of each block as well, but that would be tempting fate for someone of my clumsiness.

...having a bit more time to meddle with this over the Christmas break, I decided to take the plunge and comprehensively remove all the bits that were holding this pickup together.

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It did no good though. I still couldn't get the circuit board off the back to look inside. I guess you have to unsolder all these points as well, and I wasn't going to attempt that.

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I did some further peering, prodding and cleaning, but it made no difference. I'd tried a couple more places to see if I could get someone else to take a look at it, but no luck there either.

I wasn't ready to abandon the '80s MIDI guitar dream though, so I trawled Reverb and found someone willing to haggle a bit and sell the guitar part separately from his dodgy module. (They didn't have the cable either; no-one does.) This project was ending up costing more than I'd planned, but the prospect of a change of G10 was very tempting. I'd been getting fed up with trying to tie knots in the guitar strings in the right place to try and fix them at the points where the restraining blocks were missing, and with the damaged screw holes - and trying to dismantle the ultrasonic pickup was definitely wearing thin.

This other guitar was untested, but looked in good condition, so I thought, oh well, yeah, let's do this. Within hours it was paid and posted - job done, and I was looking forward to finally getting my hands on a (hopefully) working system.

:)

Then I made a major mistake.

I thought to myself, "what if", and took a close look at the input connector on the G10C module under a lamp.

Yup. One of the pins was missing.

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I checked the service manual to see if it's needed, and well, yup, the descriptions definitely talk about 15 connections, not 14.

That is so annoying. :headbang:

If that's now the reason behind the string error, it's some kind of infuriating coincidence, because my troubles definitely began when that string slipped its moorings.

I guess it's possible that the string error is with the guitar, but this missing pin is some other problem waiting to bite me on the ass once I've got that sorted.

At least I guess TV repair man might be willing to take a look at that one.

Grrr.

*edit*

Well, hmm, I dunno. I might have got away with it. The corresponding socket on the cable doesn't seem to have a connector, at either end...

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Maybe it's unused after all...? Just have to wait and see.
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Re: Yamaha G10 Repair

Postby Wonks » Thu Dec 27, 2018 11:53 pm

They'd certainly have mentioned a 15-pin connector in the descriptions, but that doesn't necessarily mean all 15 pins were connected.
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Re: Yamaha G10 Repair

Postby BJG145 » Fri Dec 28, 2018 12:00 am

OK! I've been flipping through tables like this in the service manual...

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...but I don't really understand what I'm looking at, so I think I'll just keep my fingers crossed. (There's no ID I can see on the plug except the numbers; the missing one seems to be number 15. I'm encouraged by the apparent lack of corresponding connections on the cable anyway.)

This is the new one I'm waiting for...

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Very excited! It's being sent from the US. Not looking forward to the customs charges.
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Re: Yamaha G10 Repair

Postby BJG145 » Tue Jan 08, 2019 8:19 pm

I got the ransom note from Parcelforce. The replacement G10 has arrived at the local depot and is being held pending the payment of additional customs, VAT and handling charges of £75...ouch. This one had better work.

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This system recently sold on eBay in Australia, and they thoughtfully included a close-up of that guitar input socket which clearly shows the same absent pin. So at least that's good.

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Re: Yamaha G10 Repair

Postby blinddrew » Tue Jan 08, 2019 10:59 pm

good luck!
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Re: Yamaha G10 Repair

Postby BJG145 » Wed Jan 09, 2019 10:58 pm

Damn these things are finicky. My heart sank when it initially stuck on the dreaded "NG" string error, albeit with a different string. But a new string and half an hour's tinkering finally rewarded me with the G10C's equivalent of the one-armed bandit's three bells...the mythical all-clear.

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Having got that far I was finally able to hook it back up to Blue 2 and play some of my trademark simpleton pentatonic licks.

https://soundcloud.com/qchord/g10

I would urge anyone who discovers this thread and is considering getting one of these things to think again, and try something simpler like the Uilleann pipes. I haven't begun to finesse the settings, but I reckon it'll take a lot of work to get it playing as smoothly as something like a Fishman TriplePlay or Jam Origin on a standard guitar.

Something in me rebels against synth sounds on a Strat, while the G10 does perhaps have the retro-futuristic look to carry it off. The clashing chorus of six strings tuned to F# is pretty bad though, and I think I'd have to swap my headphones for closed-backs to drown it out.

I still like it, and somehow just the challenge of getting the damn thing to work at all endears it to me. In general, I suspect the problem-solving side of music tech attracts me to the subject as much as the musical side.

At least I feel I've tamed this b*****d to some extent now, so even if it won't work in the morning, this evening I'm happy.
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Re: Yamaha G10 Repair

Postby zenguitar » Thu Jan 10, 2019 1:14 am

Well done :clap:

Where's the Lion Tamer emoji when you need it?

Andy :beamup:
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Re: Yamaha G10 Repair

Postby blinddrew » Thu Jan 10, 2019 9:29 am

BJG145 wrote:I would urge anyone who discovers this thread and is considering getting one of these things to think again, and try something simpler like the Uilleann pipes.
:bouncy:
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Re: Yamaha G10 Repair

Postby ef37a » Thu Jan 10, 2019 11:36 am

Masochist!
Good work though. Re the cable: Someone here (Will?) will recognize that connector. What is its diameter? If you can find those it would be good to make up a spare cable. You could scrap a Scart cable or use two CAT 5 shielded cables, gives you 8 pairs plus two drain wires.

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Re: Yamaha G10 Repair

Postby Sam Spoons » Thu Jan 10, 2019 12:20 pm

edit :- I was wrong.....
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Re: Yamaha G10 Repair

Postby BJG145 » Thu Mar 28, 2019 10:02 am

Just thought I'd mention this G10 system that's just appeared on eBay. Nothing to do with me, but if it is indeed fully working as indicated, it could be a bargain at that price. Having kept the faulty spare, I could supply the missing cosmetic bits and expert advice (*cough*) for a very reasonable fee... ;)
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Re: Yamaha G10 Repair

Postby BJG145 » Thu Mar 28, 2019 10:56 am

(...though having said that, I should warn that it's apparently missing several of the slim metal blocks that sit over the strings and clamp them down. Someone would have to try and improvise something for that...)
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