Battarypack Electribe EMX

Ruso · Post by **Ruso** » Tue May 20, 2008 5:55 am

you know to be honest I'm not sure.... the original battery I used was very dead... I assume the tubes ran because the lights turned on(behind the tubes, which did not happen any other tests I did)... but the electribe wasn't hooked up audio for me to test..

This hope is what got me to go get a fresh battery which fried it...

my room still kind of smells like it

Borg · Post by **Borg** » Tue May 20, 2008 10:22 pm

Well, can't you see that by looking at the schematics if the lights turn on if the current passes through the tubes?

gmeredith · Post by **gmeredith** » Wed May 21, 2008 12:29 am

More updates:

I downloaded the full schematics for the EMX.
The schematics show that the tubes HEATING elements are powered by DC (6V), but the actual tube's amplifying guts are powered by + and - 12V DC

So Ruso's observations did show the tubes appearing to light up, which could easily lead to the assumption that it was working fully - but since he mentioned that he didn't try the audio, I can predict that you will find that it doesn't work.

So although you will see the valves light up, they won't work as amplifiers - so you'll get no sound output from them out of the master outs.

This is shown also on p6 of the service manual, in the very centre of the page, in a box marked "tube PCB"

You MAY get an output out of the individual outs - I say this only because it doesn't show on the schematics any power rails connected to them - they may be single rail, but I doubt it. I would bet that they're + and - 12V DC also. At least you can test this though - power it up on the normal X-tribe power pack, allocate a sound to the individual outs, save your setup, then power down and use the battery pack. If you get sound out of the individual outputs, then at least you've got something for all your trouble. But I suspect not.

This is rapidly becoming the scenario that I first guessed when I joined in on this topic. Although it is not initially using a split rail power supply, it produces a split rail +,- 12V DC further on in the circuit, from the AC power fed into it, just for the audio boards. Everything else is DC.

*IF* this is the case, then you won't be able to run the X-tribes off a single battery pack.

AND - more bad news - you won't be able to hook up a dual battery in split rail config. directly to the power socket like Ruso did with the single battery - note this - YOU"LL START A FIRE!!!

This is because the 4 pins in the socket AREN'T in a split rail config - they're combined together to make only 2 pins in reality. Connect the 3 rails of a split rail battery system to these 4 pins, and 2 of the 3 battery terminals will short against each other - BLAMMM!!

In order to hook up the split rail battery system to the X-tribe, your'e going to have to open it up and tap into a specific point on the power grid for the batteries. Do it anywhere other than at this specific point, and you'll get the same short-out battery situation. I believe that these points are on p4, up the top of the page.

In a split rail battery configuration, you will have 3 battery terminals: +12V DC, 0V DC, and -12V DC. From p4 of the service manual, the +12V DC rail will attach to the circuit just directly to the left of capacitor C88. The -12V DC rail will attach to the circuit just directly to the left of diode D10. The 0V rail will attach to any convenient analog ground point in the circuit - such as the ground end of capacitor C105, which is right next to diode D10.

This battery mod is not going to be easy, but it's not impossible. But it certainly won't be the dream you all hoped for. You're going to have to disconnect each battery from the X-tribe AND from each other whenever you want to charge them - or else build a split rail DC charger

Please DON"T ASSUME I am completely correct in all this - I don't own an X-tribe, so I've never seen inside one. And I wouldn't call myself a elecronics expert - I've built stereo amplifier kits, and some guitar pedals and stuff, which is where I understand the power supply stuff from, but that's about the limit of my knowledge. And I can read simple schematics.

If anyone wants to try and continue on with this split rail battery setup, consult someone with enough knowledge who can guarantee you that this will work before you try it - I would hate to see you all fry your gear on my advice! AND then also beware of the high voltage warning about the tubes that I mentioned before!!

Cheers, graham

Ruso · Post by **Ruso** » Thu May 22, 2008 3:18 pm

great info, thanks a lot... so I guess it looks like the best option would still be to use electribe's power supply and a power inverter....

we're starting to drift off the realistic portable goal in that case and turning into a backpack deal. Still not too bad.

4NDRW · Post by **4NDRW** » Thu May 22, 2008 4:41 pm

*reads whole topic*

whoa, well most of the stuff i was gonna reply with is now irrelevant.

i know we made little amplifiers in highschool electronics class
that had to use 2 9v batteries to make it split rail
and i know how simple dc rectifiers work
so i can see how providing dc into it (if its anything like a rectifier)
can still produce dc out

and i can see that if it needs a negative rail
it cant get that from nowhere...

so to sum it all up..
sounds like the (theoretical) options would be...

*find the parts of the circuit that convert AC to DC
and supply the correct DC voltages to each part

*bypass the audio section that requires the negative rail
see if you can make some sort of seperate audio output or somethin
(maybe the individual outs do work?)

*dont touch the insides of the box at all, and use some form of DC -> AC inverter
preferably if you can find one that goes to 9V 50-60Hz AC
rather than going up to household voltage and then back down to 9VAC with the supplied adapter
as it would be a smaller package, and be more efficient

the last option sounds by far the safest..
give the unit what it wants, and let it do the conversions.

(ps. my electribe sx arrived a few days ago

)

AmigaHeretic · Post by **AmigaHeretic** » Fri May 23, 2008 12:16 am

4NDRW wrote: *dont touch the insides of the box at all, and use some form of DC -> AC inverter
preferably if you can find one that goes to 9V 50-60Hz AC
rather than going up to household voltage and then back down to 9VAC with the supplied adapter
as it would be a smaller package, and be more efficient

Well, at BestBuy you can buy an AC inverter that goes from 12v to 120volts AC for like $15. Sooooo... I think it is not in the realm of sciencefiction to believe to go from 12v dc to only 12v AC would be very hard. So I think this idea is best to. Though I have no idea how to build the circuit.

Did do some googling and found some diagrams of pics for 12v to 220v so I'd imagine someone smart could figure out how to reduce the volt to 110v or 48v or even 12v from the diagrams. But???
http://circuit-electronic.blogspot.com/ ... -100w.html

Larger version... http://bp1.blogger.com/_BQac7gcHPK0/Rcq ... 0-100w.jpg

Larger version... http://bp1.blogger.com/_BQac7gcHPK0/Rj2 ... sistor.jpg

Also found this http://www.thefarm.org/charities/i4at/lib2/inverter.htm

plosive · Post by **plosive** » Fri May 23, 2008 2:59 am

now we appear to have a serious discussion begining.

Ruso · Post by **Ruso** » Fri May 23, 2008 3:06 am

*dont touch the insides of the box at all, and use some form of DC -> AC inverter
preferably if you can find one that goes to 9V 50-60Hz AC
rather than going up to household voltage and then back down to 9VAC with the supplied adapter
as it would be a smaller package, and be more efficient

totally agree, why would you ever want to go 9 volt -> 115(or 240) -> 9 volt again, makes absolutly no sence.

gmeredith · Post by **gmeredith** » Fri May 23, 2008 4:08 am

OK, there are some great ideas happening here!

To make an AC inverter that goes from 12V DC to 9V AC is dead easy! I will refer to the bottom schematic shown by AmigaHeretic (the one from www.thefarm.org)

The transformer T1 shown as a "120V AC out" can simply be substituted for a transformer that outputs 9V AC out. In essence, it's that simple. The only thing you need to make sure of is that the power transistors Q1 and Q2 are of sufficient current rating to handle 2-3A at 12V DC. Plenty of power transistors, especially for car applications, can handle this sort of current constantly. And also, that the transformer is rated also at 2-3A output at 9V AC. Again, they're common.

This is a great idea the more I think about it. It really would be then suitably adapted to ANY low voltage AC powered synth or drum machine. The alesis equipment comes to mind, with their annoying 9V AC plug packs.

Let's keep looking around for some more designs - perhaps someone has already made one.

**EDIT** here's one that's getting close:

http://www.powerstream.com/inv-12dc-24vac.htm

They mention that they can do custom voltages.

Cheers

gmeredith · Post by **gmeredith** » Fri May 23, 2008 4:47 am

I actually found the full page notes for that simple large circuit at the bottom of Amiga's post:

http://www.aaroncake.net/circuits/inverter.asp

It gives a full parts list of suitable components, including the transistors, etc. The schematic is specifically for 12V DC to 120V AC, but he says that all you do for other AC output voltages is choose a different transformer. There's also a forum.

Reading through the forum, the suggested transformer would have a 12V-0V-12V centre tapped primary* coil, and a 9V single secondary* output coil, capable of handling 3-4A AC (ie. about 40W), regarding the diagram.

*Note that, in our application here, that the terms primary coil and secondary coil described here are actually the opposite to what you would ask some one in the shop for when buying it. This is because the transformer, in this circuit, is reversed to how you would normally use a transformer. You would ask them for a "transformer with a 9V single primary coil, and a 12V-0V-12V centre tapped secondary coil, 3-4A please" - and then they would understand what the hell you were asking for. You'll confuse them if you ask for it in the way we're using it here!

Cheers, Graham

AmigaHeretic · Post by **AmigaHeretic** » Fri May 23, 2008 5:52 am

Ruso wrote: totally agree, why would you ever want to go 9 volt -> 115(or 240) -> 9 volt again, makes absolutly no sence.

Which is really what I'm doing now. I have my Geek Squad UPS which runs on probably a 12volt DC battery inside and it converts to 110V AC, then I plug my EMX's wall adapter and it down converts to 9volts AC. Not effiecient, but it works.

Just would be nice to make it all smaller and more portable.

AmigaHeretic · Post by **AmigaHeretic** » Fri May 23, 2008 5:54 am

gmeredith wrote:I actually found the full page notes for that simple large circuit at the bottom of Amiga's post:

http://www.aaroncake.net/circuits/inverter.asp

It gives a full parts list of suitable components, including the transistors, etc. The schematic is specifically for 12V DC to 120V AC, but he says that all you do for other AC output voltages is choose a different transformer. There's also a forum.

Reading through the forum, the suggested transformer would have a 12V-0V-12V centre tapped primary* coil, and a 9V single secondary* output coil, capable of handling 3-4A AC (ie. about 40W), regarding the diagram.

*Note that, in our application here, that the terms primary coil and secondary coil described here are actually the opposite to what you would ask some one in the shop for when buying it. This is because the transformer, in this circuit, is reversed to how you would normally use a transformer. You would ask them for a "transformer with a 9V single primary coil, and a 12V-0V-12V centre tapped secondary coil, 3-4A please" - and then they would understand what the hell you were asking for. You'll confuse them if you ask for it in the way we're using it here!

Cheers, Graham

Awsome work! I would be cool if we could figure out what parts, get a parts list togther, and then post a real easy schematic of how to build it.

Borg · Post by **Borg** » Fri May 23, 2008 12:59 pm

Well I guess I can't contribute to this topic anymore. Turned out to be a bit more complicated than I thought. Nothing I'll be able to do on my own. When schematics and building stuff from stratch I'm lost. But when you guys comes up with the complete solution I could buy the parts, print out the schematics and let a friend do it for me.

Thanks a lot! You're putting down a lot of effort.

4NDRW · Post by **4NDRW** » Fri May 23, 2008 6:54 pm

*is reminded of electronics class again*

didn't think it would be so simple lookin.... but makes sense

we used that whole thing with 2 transistors with middle pins crossed over and 2 capacitors for the bottom half of that circuit in several simple circuits
from 2 LED flashers, to a simple (and s**t sounding) audio oscillator

not sure what sort of waveform it would produce, (ideally a nice sinewave)
you could check under an oscilloscope, but it probably doesnt matter

but yeh
if someone knows what all the component values are?
this would be really easy to make.

4NDRW · Post by **4NDRW** » Fri May 23, 2008 7:01 pm

so, the first circuit...
i can see the 2nd circuit inside the first one

why is it so much bigger?

is it because it provides a higher wattage?