AW: electronics question for the tech-heads.

["Rainer Thelonius Balthasar Straschill" <rs@moinlabs.de>]

Title: Nachricht

You can try and shorten the pin to the GND pin with a precision potentiometer (of which you are sure to turn it to maximum resistance before powering up). Then you can measure the voltage between power and GND pin while slowly turning the resistor to smaller Ohm values, until the voltage starts do drop. Then you disconnect the potentiometer and measure its resistance value. By using Ohm's law, you get the current the source is able to handle by I=U/R.

 

Wouldn't want to tell you this can be done without any risk whatsoever, though...you might start with a 250kohm logarithmic pot. Also consider that the components (mostly semiconductors) will heat up and then degrade temporarly in performance, so after you got you measurement, subtract 20-25% to be on the safe side.

 

You might also take apart your GK "host" and have a look whether you can find out which component supplies the power supply to the pickup. Or you could jury-rig your GK device and feed the power with a reliable power supply (say, a 7V/1.5A supply which I'd assume would be good for ten guitars)-

-----Ursprüngliche Nachricht-----
Von: mark francombe [mailto:mark@mark-red.com]
Gesendet: Samstag, 12. Februar 2005 14:57
An: loopers-Delight@loopers-delight.com
Betreff: Re: electronics question for the tech-heads.

Good point Brian, but would it be risky to "try", could i blow something? Checking thru the spec of the GK pickup (that would be providing the power) there is no mention of power requirments at all, I guess it has "no user servicable parts" therfore no info...

(how do i check the amperage anyhow?my simple multimeter doesnt seem to have that on it..)

 

Mark

 

Risky...You also have amperage to consider. Will the source be able to handle the amperage that the pickup draws?

 

I think your best bet is to contact the manufacturer for the specs.

 

Brian

 

 

----- Original Message -----

From: mark francombe

To: loopers-delight@loopers-delight.com

Sent: Friday, February 11, 2005 4:33 PM

Subject: electronics question for the tech-heads.

Sorry for Off topic..

 

After a few weeks of completely happy and crazy use of my newly installed (and now working, thanks to LD people) Fernandes Sustainer pickup, I have for the first time left the damn thing plugged in overnight, (battery switch on jack socket arrangment) and drained the battery. THIS WILL NOT DO! now I could add a power switch to the guitar (but then I would no doubt forget that ..)

BUT... I have a cunning plan!!!

I also have a GK midi pickup installed on the same guitar, and when I poke around with the multimeter at the socket that is installed in the guitar that takes the midi to my synth I find a pin that seems to have around 7 volts sitting there. The sustainer pickup taks a 9 volt battery (but when I test, again with multimeter) it also appears to be around 7 volts.

 

Now it doesnt take an idiot to realise what I'm suggesting. I would like to take the power from the GK midi pickup cable and connect it to the sustainer. Which I would have tried already, but for one little prob.

 

If I check voltage on the battery with multimeter connected with BLACK cable to ground and RED cable to battery.. 7 volts. When I do the same on this mysterious power wire inside the GK connector, the multimeter trys to swing the wrong way, I reverse the multi meter leads, and then I get this reading of 7 volts.

Does this mean that the GK pickup is infact powered by -(minus) 7 volts? ( I've never really understood the concept of negative volts Im afraid..) SO.. either I cant use this power, OR I must reverse the polarity of it???

 

Is this possible?

 

Wise?

 

Foolish?

 

Help?

 

 

 

 

Mark

 

 

 

mark francombe
www.markfrancombe.com

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