APX6 problem

APX series guitars are designed with a focus on playability. Their thin bodies and cutaways that provide greater access to the upper frets, offer smoother switching between electric and acoustic instruments.

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HarryEvan
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APX6 problem

Unread post by HarryEvan » Fri Feb 07, 2014 4:18 am

I've got an APX6 that I bought back in '88 (I think) and when I use it with a pedal or another 9 volt device, strange things happen. With a Zoom 505 a few years back, the battery in the guitar nearly exploded. When I used a Boss TU-12 tuner, it reversed the polarity of the meter (got the tuner back with a VOM, don't ask how) and plugging it into a Vox Mini 3, it reversed it's polarity, which I got back with the VOM (wish I knew how I did that one).

No one at Yamaha had a clue, but a tekkie with Zoom said it might be the way the power switching is set up in the guitar. With that, and the subsequent problems, I was thinking maybe it's in unplugging at the guitar first, rather than the pedal or amp, just a shot in the dark.

My brother has an identical APX6, but I haven't found out if he's encountered any problems. Before I use it with a wireless, I thought I'd explore things a bit more, and this time Yamaha sent me the service manual (attached) and said, "Hope this helps." Thought it might help someone here, too. Anyone have anything similar to this happen to them?

HarryEvan
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APX6 n-SYSTEM20_20L_21_SM.pdf
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Saul
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Re: APX6 problem

Unread post by Saul » Fri Feb 07, 2014 11:42 am

Not experienced any problems like that myself, although I have a CPX700 so may not be quite the same. Seems like the other 9 volt equipment your using is being allowed to send too much power to the guitar. Given the age of the guitar my guess would be a component failure, perhaps capacitor or diode both of which are cheap and easy to replace. I'm no electronics guru but I would be looking at a diode since these are designed to allow current to flow in one direction and inhibit it's flow in the opposite direction.

We have plenty of people on the forum who are far better qualified than me to advise on this and I'm pretty sure one of them will pick this up and be able to guide you in the right direction soon.

Thanks for posting the pdf by the way :)
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Re: APX6 problem

Unread post by Buzzard » Sat Feb 08, 2014 1:34 am

Welcome Harry.

That's a tricky one.
Usually the negative/ground is disconnected when the plug is removed.
That goes for the output in guitars with active pickups and also for the input plug on most pedals.

If all plugs and cables are in good shape, the circuits should not mix their current in any way. (be sure to use MONO cables)

First test the guitar, plug a cable in and use a voltmeter on the other end of the cable to see if there is any voltage at all.
There should be none, or at the most a very small voltage.

If this is ok, plug straight into an amp (no pedals) and see if there is sound, and if the guitars circuitry and battery behaves normally.

Try different amps if possible.

If it works ok so far, is suspect that you may have used stereo cable(s) or you pedals may have the fault,
but if you have different guitars known to be in good working condition use them to test the pedals with an amp.

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Peter
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HarryEvan
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Re: APX6 problem

Unread post by HarryEvan » Sat Feb 08, 2014 4:05 pm

Thanks, Peter, but I went through all of that. I just had the preamp out and inspected it as well, but nothing seemed to be a problem there, either. I did disassemble the jack and there can be a situation where the tip of the plug is touching both contacts if the plug isn't pushed in all the way (these guitars have always been a little difficult to get the plug all the way in) or removed quickly. I did remove the second layer of insulation within the jack, which makes it easier to get the plug in quickly. I think I would have made the switching contact a little longer so that this doesn't occur (hindsight). But removing the jack has definitely loosened it up in the wood surrounding the hole, so it may be a problem in the future. After the work, I tried it in the tuner and all seems well, so far.
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Re: APX6 problem

Unread post by Buzzard » Sat Feb 08, 2014 10:19 pm

Hi Harry.

Do you now have a working guitar with a loose plug ?

Is there a way you can fasten the plug ? , if not , better get a replacement.

Here's a picture of the plug in my APX-500 II , combined plug and strapknob, AND with 2 small screws to hold it in.
Maybe this part can be used for your guitar, and since this model is still in the shops, spareparts should be available.

Image

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Re: APX6 problem

Unread post by parametric » Sun Feb 09, 2014 4:10 am

For sheer functionality - I'd recommend fitting a Neutric LOCKING jack socket. Plugs in easy, but you must press a little release tab to take the plug OUT. No more accidental unpluggings.

Probably NOT an option if, like me, you prefer to keep it "original" (if its a collectible or rare guitar).

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HarryEvan
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Re: APX6 problem

Unread post by HarryEvan » Sun Feb 09, 2014 5:13 am

Actually, I had a working guitar to begin with, just had a glitch with pedals and tuners that I'm working around. I didn't think the jack was just pressed in, rather threaded and screwed in like a Highlander's jack/preamp. A little wood glue or something will do the trick.

That I was able to loosen up the mechanism of the jack by removing the extra layer of insulation helps quite a bit more - it had always been a problem to be sure the plug was fully seated in the jack as the extra layer made it extremely tight, always felt like it was in, but it had to go the extra click. That the longer contact couldn't have been a bit longer to avoid the momentary short was someone's oversight and there's not enough to work with to improve it.

Just have to be quick, especially in disconnecting from the guitar. With the tuner and other devices, you can disconnect at their end first, but I've got this wireless that can't be easily (maybe quickly or gracefully would be better terms) disconnected on stage. Will just take some getting used to.

Both those jack options would require a bit more work than I want to do, rewiring the jack. Neutrik 's hardware is pretty good stuff, but the jack is still tight enough that it's not going to accidentally disconnect, by any means. It's as difficult to remove as it is to seat.

And this guitar was the low-end model with the cutaway, though I never saw a price tag on an APX5, so, unless my grand-daughter were to find a very eccentric collector in her old age, it won't ever be worth more than the $325 I paid for it (including the gig bag) all those years ago. It still plays well, the intonation is right, I've only had to adjust the relief in the neck once and it sounds really good plugged into an amp or a P.A. (actually, it sounds good acoustically if you're standing in front of a glass door), it's very light and even the tuners are holding up after all these years.

I've only come across one item with the Yamaha brand on it that wasn't quite up to snuff - an older 500cc, twin cylinder motorcycle from the 70's. It was nothing like the 650's they admittedly copied from BSA, Triumph, Norton and Royal Enfield. A dog, must have tried something "original". Three tuning forks...
Harry Evan Vermillion
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Saul
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Re: APX6 problem

Unread post by Saul » Sun Feb 09, 2014 4:07 pm

I remember that old Yamaha XS500 very well. It's biggest problem was the overly long timing chain that would stretch and snap. The XS650, which I also had was a really nice bike but could be a complete pain in the ass to start sometimes but at least it didn't constantly leave a puddle of oil wherever it went, unlike the British counterparts it was based on.

Hope your APX issues are sorted. The whole APX range are great guitars, even at the budget end. Can't say I have ever come across a bad Yamaha guitar at least not so far. Quality control seems to be high no matter where they are built.
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