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'null'
2003\02\24@065646 by Rick C.

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subject=Re:[OT]: Korg Digital Piano
source= http://www.piclist.com/postbot.asp?id=piclist\2003\02\23\121855a

I would also suspect the power supply. A quick way I check the capacitors is to put a variac on the power input (as long as it is a linear supply) and reduce the input voltage to about 95 volts. This drops the headroom and thus the ability of the filters to provide stable clean power. If the unit acts up, the electrolytics are suspect.

I have an incomplete lecture on just such a problem with keyboards at:
http://www.pic101.com/ensoniq/pswoes.htm

Rick


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'null'
2003\03\03@071649 by Rick C.
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subject=Re:[EE]: Headphone out to RCA line-in converter
source=I have dozens of computers at the radio station I engineer and do
exactly the same thing you are doing with little or no hum or noise.

Make sure you are not using a RCA "phono" input and verify that the line input is of correct levels. Try another source like a portable tape or CD player to verify this.

Buzz or hum could be also a ground loop problem. Grounding both
chassis is not always a good idea because of mains differences.

I doubt the noise is coming from the power supply itself. My Sony VAIO laptop headphone output is clean and has no bandwidth
problems. I can plug it into any audio amplifier and have excellent results.

Using good quality isolation transformers will almost always cure the problem. Jameco has some cheap ones for a few bucks each but the low end suffers a little. Broadcast quality transformers could get pricey but you could find some cheaper on ebay. Almost
any impedance transformers can be used. 600/600, interstage (1k/1k, 2k,2k, etc.) transfrmers are less lossy. Just make sure
they are identical for both channels. If the levels are too high
and you hear distortion on peaks, you may have to pad the input with resistors to drop the level.

Lastly, make sure you are using a good and tested patch cable.
I had a problem once and found that the ground shield was open
between the two sleeves.

Rick




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2003\03\03@073259 by Rick C.

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subject=Re:[EE]: Lead-Acid accumulator pulser against sulfate-cristallization
source=I use these devices all the time. They do work! They are called
desulfators and you can buy them off the shelf or roll your own.

One nice one is from http://www.vdcelectronics.com for about
US$45.00. I have about twenty UPS supplies at work and every two
years I cycle the batteries out, desulfate them, and cycle them back in. I have taken old open gel cells and brought them back to
life again. Lawnmower batteries typically last about three years
before they die. Putting the device on the battery for a month
over the winter brings it back to new again.

I have a 48 volt 2000 amp battery system backing up my home and
use a beefy desulfator on them permenantly. They will extend the
life (9 years) to almost double (15 years).
www.mrsolar.com/batteries/desulfator.htm
roll your own here:
http://www.shaka.com/~kalepa/desulf.htm

Good luck.
Rick


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'null'
2003\05\12@115811 by Dave VanHorn
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At 11:51 AM 5/12/2003 -0400, Mike McLaren - K8LH wrote:
>subject=Re:[PIC]: Oscillator options, or Oops, I bought a series XTAL!
>source= http://www.piclist.com/postbot.asp?id=piclist\2003\05\12\093224a
>
>So, Gentlemen, is a DigiKey X443-ND (18pf) a 'parallel cut' crystal???  Is
>there a way to tell in the DigiKey catalog???

If it spec's a load capacitance, it's parallel.
The ones that don't are series.

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