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Battery Drain W/variax Off


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#1 pheld

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Posted 25 April 2013 - 11:03 PM

Why does the battery drain so quickly with the 1/4" connected and variax switched off? Ideally there should be no need for power at all when the guitar is switched to magnetic pickups regardless of whether the instrument is plugged in or not. Also the "power-saving" feature that supposedly takes effect when the volume is rolled off doesn't seem to help much. My JTV59 drains completely over night if it is plugged in, is on magnetic pickups and with the volume on 0. Just like it would if I had been playing with variax-models all night. It's ok if I pull the plug, but that should imho not be strictly necessary. It may be that the variax-circuit requires a few seconds to boot so that it would be too slow switching back and forth between piezo and magnetics if the circuit had been completely powered off, but a power-saving circuit should still bring the consumption to near 0 when it is not used.


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#2 phil_m

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Posted 26 April 2013 - 03:43 AM

It's just the nature of lithium ion batteries. Because the terminals of the battery are connected, there's still leakage from them even if the circuit downstream isn't closed. Even a lithium ion battery sitting by itself loses charge slowly. Pulling the 1/4" definitely helps. You have to think of the Variax like a guitar with active pickups. If you leave that type of guitar plugged in overnight, the battery will die quickly as well.


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#3 silverhead

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Posted 26 April 2013 - 06:43 AM

..... Ideally there should be no need for power at all when the guitar is switched to magnetic pickups....

I don't think that's true. When switched to magnetic pickups, the Variax OS (it's a computer, after all) still has to be cycling and 'listening' for the command (Model Select knob depression) to instantly turn on its modelling. It's akin to having your laptop computer running and being able to repsond to your keystrokes instantly, even though you may temporarily be reading a book instead. If you want to turn off your computer completely you need to power it off (unplug the guitar cable).


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#4 toneman2121

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Posted 26 April 2013 - 08:33 AM

if there is a way for electricity to flow it will find it. a small light in your car; glove box, trunk. will drain a relatively new battery overnight. is your battery new?


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#5 pheld

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Posted 26 April 2013 - 04:19 PM

I don't think that's true. When switched to magnetic pickups, the Variax OS (it's a computer, after all) still has to be cycling and 'listening' for the command (Model Select knob depression) to instantly turn on its modelling. It's akin to having your laptop computer running and being able to repsond to your keystrokes instantly, even though you may temporarily be reading a book instead. If you want to turn off your computer completely you need to power it off (unplug the guitar cable).

Which point I made in the original post. Any computer that requires some form of boot sequence will have to be kept alive to respond within reasonable time in a real-time environment. However, my experience with embedded computer design says that it should be possible to conserve 95% or more of the operating consumption by dropping the clock from GHz to kHz and still be able to wake the device up in less than 1ms when necessary. In this case the switch could generate a direct interrupt to the circuit and it should be able to react fully within a couple cycles. So I wonder why the battery drains nearly as quick when the variax circuit is off as when it is in full operation. It's not unusual for a device that operates for 10 hrs on a battery to stay alive in standby (active but running very slow) for 500hrs or more on the same charge. Measuring current I see about 15-20% reduction with the variax off and volume on 0, which is very far from the reduction seen on many other types of circuits in standby-mode.

 

I'm happy with my JTV. Like with many new guitars it'll take a plek-job before I can get the action as low as I wish, but other than that I have no complaints. It's just that I'm reading about "power-saving features" and can't really find any. 


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#6 pheld

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Posted 26 April 2013 - 04:37 PM


It's just the nature of lithium ion batteries. Because the terminals of the battery are connected, there's still leakage from them even if the circuit downstream isn't closed. Even a lithium ion battery sitting by itself loses charge slowly. Pulling the 1/4" definitely helps. You have to think of the Variax like a guitar with active pickups. If you leave that type of guitar plugged in overnight, the battery will die quickly as well.


Any battery drains over time even if it is placed in a vacuum where electrons can't travel, because all known battery constructs have internal leakage. Lithium-ion in general is actually a lot better than many other technologies in this respect. The problem arise with rechargeable cells which shouldn't be discharged below a certain voltage, or they will loose their ability to take charge. To avoid that the equipment, and sometimes the batteries themselves, have a built-in circuit-breaker. A small amount of energy will leak through this circuit, but it is minuscule in most modern battery designs, and certainly insignificant compared to the load of an operational or even "sleeping" variax. 

 

A 1/4" jack used as a power-switch should be a stereo-jack, and wired so that neither the amp nor the magnetic pickups become part of the circuit. I.e. any leakage should happen within the internal circuitry. The variax supposedly has powersaving-features, unlike a plain guitar with active pickups so they don't compare at all. I've got other guitars with active circuitry that uses the jack as power-switch, but there's next to no drain on the battery with the jack plugged if the built-in circuit has powersaving features or other internal power-switching (hardware or software).


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#7 pheld

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Posted 26 April 2013 - 05:35 PM

if there is a way for electricity to flow it will find it. a small light in your car; glove box, trunk. will drain a relatively new battery overnight. is your battery new?

The battery is as new as the guitar. It has about 10 charging cycles so far. I have no clue when it was made. I may replace it with an external powersupply feeding through a custom stereo-cable as part of some mods along with new magnetic pickups and coil-tap switches.


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#8 toneman2121

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Posted 26 April 2013 - 06:45 PM

so your question is rhetorical


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#9 davidb7170

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Posted 27 April 2013 - 11:24 AM

Actually, the battery & electronics go into a low power state (not off) when you roll the volume off on the JTV, and the model knob flashes every few seconds. This is like closing the lid on your pc -- puts it into sleep mode. In that mode, the pc is in a low power state. If you leave it long enough in that state, the pc battery will eventually discharge. To disconnect the battery on the JTV, simply unplug your 1/4" plug from its jack -- it's like active pickups like EMG that get turned on by plugging it in. Even with the volume down, there is drain on those batteries, too... Try it. If your battery still drains, then you might have a battery or internal connection problem with the JTV.

 

My 2 cents.

Dave


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#10 pheld

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Posted 27 April 2013 - 01:49 PM

Actually, the battery & electronics go into a low power state (not off) when you roll the volume off on the JTV, and the model knob flashes every few seconds. This is like closing the lid on your pc -- puts it into sleep mode. In that mode, the pc is in a low power state. If you leave it long enough in that state, the pc battery will eventually discharge. To disconnect the battery on the JTV, simply unplug your 1/4" plug from its jack -- it's like active pickups like EMG that get turned on by plugging it in. Even with the volume down, there is drain on those batteries, too... Try it. If your battery still drains, then you might have a battery or internal connection problem with the JTV.

 

My 2 cents.

Dave

I'm not complaining that a sleeping variax is draining the battery, just trying to understand why the difference between active and sleep is so small. I have just completed tests sampling current and voltage over time while the battery discharges one time with the variax active and one time with it in sleep mode (turned off with vol on 0). The sampled data confirm that the energy delivered by the battery during the 2 test-runs is the same. The time from full-charge to voltage-cutoff occur was 11hrs13min with the variax on and 13hrs24min with the variax sleeping. I would expect power-saving to achieve quite a bit more than that. All it needs to do while sleeping is to maintain RAM-contents and state, something that most recent computing devices are able to handle with considerably less than 10% of its operating power-consumption.

 

For reference: I have 2 guitars with active pickups. One has a built-in powerswitch on the volume-pot and thus doesn't pull any measurable current from the battery in 0-position. The other pulls about 2% of its maximum consumption when the volume is on 0.


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#11 toneman2121

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Posted 27 April 2013 - 02:36 PM

change the battery


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#12 pheld

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Posted 27 April 2013 - 09:54 PM

change the battery

Wich of the facts presented in this thread make you suggest that this is a battery problem? Both batteries supplied with the guitar work the same, and both charge and discharge the amount of energy mentioned in their specification (calculated from voltage/current/time-plots). I.e the battery delivers the same number of mAh regardless of whether the variax-circuit is active or in sleep-mode, while the discharge-time only varies by a couple hours. 


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#13 toneman2121

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Posted 28 April 2013 - 03:53 AM

Which of the facts presented in this thread make you suggest that this is a battery problem? Both batteries supplied with the guitar work the same, and both charge and discharge the amount of energy mentioned in their specification (calculated from voltage/current/time-plots). I.e the battery delivers the same number of mAh regardless of whether the variax-circuit is active or in sleep-mode, while the discharge-time only varies by a couple hours. 

in which post did you mention 2 batteries? has anyone else had this experience? it may be possible both batteries are defective.  maybe the sleep mode circuit is bad. maybe the charger is defective. obviously, there is current leakage if in fact there is a fault.  you will have to troubleshoot the circuit to find the fault, if any. in which case, you will have to have specifications of the circuit or compare the findings to a known good one. changing the battery will be the easiest and less time consuming. try a different cord. how do you expect anyone to answer your question when you know all the answers but still can't determine the problem. maybe it's supposed to act that way. if so, unplug it. done


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#14 pheld

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Posted 28 April 2013 - 01:15 PM

maybe it's supposed to act that way.

I was kinda hoping that someone in or related to the design team may comment on design issues, but this may very well be case. I did some more measurements today and discovered that the digital interface is active even if nothing is connected. It may boil down to the fact that there are opportunities for optimisation in future hardware revisions. 

 

I'm sorry I didn't mention multiple batteries, but a battery seems ok to me when it delivers the prescribed number of mAh in each charge-discharge cycle. Pulling the cord when the guitar isn't used is a good thing to do, but I think that especially those who play mostly magnetic pickups would benefit a lot from an improved sleep-mode.


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#15 toneman2121

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Posted 28 April 2013 - 01:22 PM

better to burn out than fade away

 

i suggest submitting a support ticket


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#16 phil_m

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Posted 28 April 2013 - 01:58 PM

Pulling the cord when the guitar isn't used is a good thing to do, but I think that especially those who play mostly magnetic pickups would benefit a lot from an improved sleep-mode.

 


I don't understand why pulling the cord isn't a good thing to do. Even if I'm at a gig, I might pull the cable from the guitar between sound check and the show. At home I always just unplug it. It just makes it a non-issue then.


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#17 katiekerry

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Posted 28 April 2013 - 04:10 PM

Yeah I always pack my guitar in its case between practices..  But I Also use the HD500 to power it  though..  But I get your gripe they kinda advertise it as a sleep mode when volume is turned down Or no battery drain.. 


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#18 pheld

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Posted 29 April 2013 - 04:13 AM


I don't understand why pulling the cord isn't a good thing to do. Even if I'm at a gig, I might pull the cable from the guitar between sound check and the show. At home I always just unplug it. It just makes it a non-issue then.

I wrote that pulling the plus _is_ wise. This is not a big issue, but I use the magnetic pickups 95% of the time and it's a bit annoying that the battery is draining quickly for no good reason. My solution is to feed power from an external adapter via a stereo cable. I may also use the leftover pickup-ring-switch from my coiltap setup as a circuit-breaker for the battery should i need to use it in the future.


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#19 toneman2121

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Posted 29 April 2013 - 05:31 AM

I wrote that pulling the plus _is_ wise. This is not a big issue, but I use the magnetic pickups 95% of the time and it's a bit annoying that the battery is draining quickly for no good reason. My solution is to feed power from an external adapter via a stereo cable. I may also use the leftover pickup-ring-switch from my coiltap setup as a circuit-breaker for the battery should i need to use it in the future.

seems like i read yesterday that you wrote "pulling the plug isn't a good thing to do". i guess phil and i read it wrong 


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#20 toneman2121

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Posted 29 April 2013 - 05:46 AM

so here are your choices. submit a support ticket, troubleshoot the circuit in the case of a fault, unplug the guitar cord, live with it. i'm sure nobody here can give you the answer  you want.

 

i think there is a fault in the circuit


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