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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Jul Wed 11, 2012 4:42 pm 
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Hi Ricky

I don't blame you for not understanding the coil. It looks just like a resistor. Notice the resistor looking device with orange, orange, brown, gold bands. That's a 330uh coil. The green one, on end, is another coil.

Looks like Tom used 2.2K resistors in series with RCA jacks. Doesn't seem like 8.2K from here? Value isn't critial. It just keeps from shorting left and right channels together.

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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Jul Wed 11, 2012 5:17 pm 
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Norm Leal wrote:
Hi Ricky

I don't blame you for not understanding the coil. It looks just like a resistor. Notice the resistor looking device with orange, orange, brown, gold bands. That's a 330uh coil. The green one, on end, is another coil.

Looks like Tom used 2.2K resistors in series with RCA jacks. Doesn't seem like 8.2K from here? Value isn't critial. It just keeps from shorting left and right channels together.

Thanks, Norm. Do you make the coil, or salvage one?

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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Jul Wed 11, 2012 5:33 pm 
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Hi Rickey

I suppose you could wind coils, but recently bought them in bulk from a offshore seller on ebay, have like $6 in 50...

Send me a PM with address & I can send you the coils... If you need most of the components, Bill Hamre also has a parts kit...

Hey Norm, those audio resistors are 8.2K 2%, there is a very hard to see gray band on the end... Still I've found something in the range of 1-1.5K to be as good as anything... The breadboard has a old pair of 1K that measure closer to 1.2K, didn't want to chop up new resistors I could use elsewhere...

http://amradio.freeiz.com/transmitter/386txled.jpg

Schematic with wallwort P/S & LED tuning indicator...

http://amradio.freeiz.com/transmitter/386txps.jpg


Tom


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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Jul Wed 11, 2012 6:07 pm 
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Thanks Tom, pm sent.

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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Jul Wed 11, 2012 6:55 pm 
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Tom

I must need a new monitor. From here I see red, red, red, gold.

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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Jul Wed 11, 2012 10:06 pm 
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Norm Leal wrote:
Tom

I must need a new monitor. From here I see red, red, red, gold.


Actually Norm if someone told me the end bands were gold, I could see their view... Gray is difficult to distinguish on the blue body...

Tom


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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Jul Wed 11, 2012 10:15 pm 
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Tom, on the schematic, which one is the potentiometer ? I see the trimmer, just a little confused.

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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Jul Wed 11, 2012 11:34 pm 
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The center tap of the pot connects to the .1 that couples signal to pin#2 of the LM386... Audio signal enters through the pair of 10K to one leg & opposite leg connects to ground... It's a common voltage divider circuit, just vision the center tap(arrow) being able to move toward or away from ground(which is exactly what it does) to allow more or less signal to enter the LM386...

Value isn't critical, you can reduce to as low as 5K as long as the input resistors are also kept at approx 20% of the pot's value...


Repost of schematic so it's easier to visualize...

Image


Tom


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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Jul Thu 12, 2012 1:03 am 
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Thanks,Tom.

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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Jul Fri 13, 2012 6:28 am 
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Hello Guys,
Ya count me into let me know what the kit will cost Sounds fun


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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Jul Fri 13, 2012 6:42 pm 
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Sounds like what I need. Where do I send the money?

Thanks,

Andy


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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Jul Wed 18, 2012 12:44 am 
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Thanks to Tom and Bill and anyone else who may be involved in this project. Mine worked perfectly the first time I applied power. It seems to rival much more complex circuits. Now on to a 120 power supply and a case.

Ed


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File comment: It would have been neater except that my dog kept bothering me. Oh yes, I don't have a dog, so substitute another excuse here.
LM 386 Xmtr (Small).JPG
LM 386 Xmtr (Small).JPG [ 94.15 KiB | Viewed 3316 times ]

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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Jul Wed 18, 2012 1:37 am 
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Quote:
It would have been neater except that my dog kept bothering me. Oh yes, I don't have a dog, so substitute another excuse here.


Looks fine to me, oversize components on a small board can be a challenge to work with...

Tom


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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Jul Thu 19, 2012 3:01 am 
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I'm finishing up the one I'm building for a friend and the 0-50pf trimmer/capacitor is bad. Anybody have a spare?

Thanks,
Larry

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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Jul Thu 19, 2012 3:52 pm 
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I'll mail you a trimmer

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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Jul Thu 19, 2012 4:20 pm 
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Thanks Bill.

Larry

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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Jul Fri 20, 2012 3:02 pm 
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hello tom,
I wondering if there is going to be a kit offered this is a great unit for me to build as a gift


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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Jul Fri 20, 2012 3:24 pm 
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Hi Rich

Anyone wanting a kit should contact Bill Hamre, he stocks a supply of parts...


Tom


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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Jul Fri 20, 2012 3:45 pm 
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Bill,
Where did you source that nice ceramic/mica trimmer?
All I see anymore are the microminiature plastic things.

-Sam T.


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 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Jul Fri 20, 2012 6:20 pm 
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Location: aston, pa, usa
Sam,

Dan's small parts and kits.

Bill

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