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 Post subject: Any neat ZN414 schematics out there?
PostPosted: Nov Sat 19, 2016 7:59 pm 
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Saw a YouTube video on this slick little chip so I picked a couple up for $5 bucks. Anybody done anything with one of these?

Pete

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 Post subject: Re: Any neat ZN414 schematics out there?
PostPosted: Nov Sat 19, 2016 8:37 pm 
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I have been playing with these for years. Also look for MK484 and TD7642.

Lots more info and activity on The Radio Board.

http://theradioboard.com/rb/viewtopic.php?f=4&t=7291

Also look for articles by Dan McGillis and Raymond Haigh

http://www.fracassi.net/iw2ntf/manuali/ ... -haigh.pdf

These are a lot of fun, but won't work well for shortwave. Excellent for AM band and VLF.

Rich


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 Post subject: Re: Any neat ZN414 schematics out there?
PostPosted: Nov Sat 19, 2016 11:47 pm 
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viewtopic.php?f=12&t=213093&p=1785094#p1785094

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 Post subject: Re: Any neat ZN414 schematics out there?
PostPosted: Nov Tue 22, 2016 1:47 pm 
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Very interesting circuit fifties.

I may have to try that tuning cap arrangement when I build mine.


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 Post subject: Re: Any neat ZN414 schematics out there?
PostPosted: Nov Fri 25, 2016 10:00 pm 
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I just breadboarded one with a TA7642, based off the standard schematic using a ferrite rod bar antenna, and a 14-389 pf cap, and even in my basement, I really was impressed with the sensitivity and the selectivity. I'm about 30 miles west of Detroit so I don't get the wash from our two power stations out here, but it was pretty darn decent! Next I'm going to couple this to an amp based off the lm386n-4 chip so I don't have to use my HealthKit t-4 to hear it. Pretty cool!


Pete

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 Post subject: Re: Any neat ZN414 schematics out there?
PostPosted: Nov Fri 25, 2016 11:16 pm 
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Very nice


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 Post subject: Re: Any neat ZN414 schematics out there?
PostPosted: Nov Sat 26, 2016 3:56 am 
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I'm starting to think this "solid state" business these kids are talking about, might stick around for awhile. Kind of like rock & roll and democracy.....
Well, one outa two ain't bad.

Pete

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 Post subject: Re: Any neat ZN414 schematics out there?
PostPosted: Dec Thu 01, 2016 12:50 pm 
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Location: Melbourne, Florida, USA
Hi Pete, I've been playing with these TA7642's for a few years now. Here is the best circuit that I've tried so far:
http://theradioboard.com/rb/viewtopic.php?f=4&t=4163&p=36519&hilit=fox#p36519

A few things I have noticed about these IC's. One is they like high Q tank circuits!
Also, I have seen differences in performance from part to part. Similar to having to test several germanium diodes to try and find the one that detects best. Same thing with these IC's. The oldest parts were the ZN414's, then came the MK's and today's TA7642's. The TA versions will go higher in frequency too!

I built a copy of the Ferrite Fox 5 and with only the ferrite rod antenna, I hear stations over 1000 miles!
By the way, for those who might want to try this IC out. There is a fairly inexpensive store bought kit that is very similar to the ferrite fox called the AM780 by Elenco. Here is the manual:
http://www.elenco.com/admin_data/pdffiles/am780.pdf

Anyway, good luck with your projects! 73 Bill NT9K..

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 Post subject: Re: Any neat ZN414 schematics out there?
PostPosted: Dec Sun 25, 2016 4:14 pm 
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Thanks Bill,
The only real issue I ran into was with the recommended 1k agc resistor, I had too much voltage present on the chip and the sound would get distorted. I changed that out to a 1.5k which dropped the voltage to .87, which was much better. I tried a 10k miniature pot there but it was too noisy and touchy, and that was all I had around here. I'm going to use a tda7267a IC instead of the lm386n-4 I used on the breadboard when I finally "hard wire" it onto a soldered perf board. Less parts and sounds better. I just started experimenting with IC's and I must say, I'm enjoying it!
I also plan on trying a lm317 to get the two different voltages required out of one battery.
I also should mention that I used the ta-7642 for the radio instead of the 414.

Fun stuff!!

Pete

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 Post subject: Re: Any neat ZN414 schematics out there?
PostPosted: Dec Sun 25, 2016 10:21 pm 
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To eliminate the problem with the 10K variable resistor connect a 100uF electrolytic cap between ground and the end of the 10K pot that feeds the MK-484 then insert a 470 ohm resistor between the pot and MK-484.

That will eliminate all noise from the 10K pot.

Make sure the miniature pot you use is multi turn otherwise it will indeed be too sensitive.

I found that as the AGC resistor is increased in size the maximum signal level the chip can handle is reduced.

With mine I had used a 4.7K which came as part of the kit I bought just for the nice PC board.

During testing I took measurements and got one maximum strength. I then used a 240 ohm resistor and the maximum signal strength was higher.

Seems I'm learning a lot about the MK-484 trying to get my circuit the best it can be.


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 Post subject: Re: Any neat ZN414 schematics out there?
PostPosted: Dec Sun 25, 2016 10:37 pm 
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BakelitePete wrote:
I also plan on trying a lm317 to get the two different voltages required out of one battery.
I also should mention that I used the ta-7642 for the radio instead of the 414.

Not sure of the requirements for the TA7642, but the original ZN414 and following MK484 like a voltage of around 1 (or as you noticed yourself, below that), and the LM 317's lowest is 1.2. That two tenths -believe it or not- can make a noticeable difference.

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 Post subject: Re: Any neat ZN414 schematics out there?
PostPosted: Dec Tue 27, 2016 3:37 pm 
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The audio chip will work ok at 9v but the RF chip is destroyed >1.8v supposedly. Currently I'm using a standard C battery for the RF and a 9v battery for the audio. My thoughts for using the regulator was to simply feed the RF chip with the 1.2 - 1.5v regulated output, and the audio chip with the straight 9v. I'll keep the 1.5k agc resistor to get me to that magic 0.87 or so VDC

Good thing, is all this stuff is cheap and easy to get!

Hey Tube, I'm going to try your recommendations, thanks!

Pete

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 Post subject: Re: Any neat ZN414 schematics out there?
PostPosted: Dec Tue 27, 2016 4:18 pm 
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You're welcome.

The regulator idea is still a good idea to use before the variable pot as it will keep the voltage to the MK-484 circuitry constant as the battery drains, but you might want to check and se how much current it draws, because if running on a battery you want to minimize the current draw so the battery lasts as long as possible.


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 Post subject: Re: Any neat ZN414 schematics out there?
PostPosted: Dec Tue 27, 2016 9:30 pm 
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Tube Radio wrote:
You're welcome.

The regulator idea is still a good idea to use before the variable pot as it will keep the voltage to the MK-484 circuitry constant as the battery drains, but you might want to check and se how much current it draws, because if running on a battery you want to minimize the current draw so the battery lasts as long as possible.

The battery should last 3 months;


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 Post subject: Re: Any neat ZN414 schematics out there?
PostPosted: Dec Wed 28, 2016 2:02 am 
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Yes for the radio circuit, but I don't know if the voltage regulator will draw any current.


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 Post subject: Re: Any neat ZN414 schematics out there?
PostPosted: Dec Wed 28, 2016 6:13 am 
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Here are the new versions for 30 cents each. If you want ten.

http://www.goldmine-elec-products.com/p ... er=G20926A


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 Post subject: Re: Any neat ZN414 schematics out there?
PostPosted: Dec Wed 28, 2016 3:32 pm 
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Very nice.


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 Post subject: Re: Any neat ZN414 schematics out there?
PostPosted: Dec Wed 28, 2016 11:26 pm 
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Macrohenry wrote:
Here are the new versions for 30 cents each. If you want ten.

http://www.goldmine-elec-products.com/p ... er=G20926A

In the 1973 magazine article, the original's were $4.95 each.

That would equal about $27.55 today.

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 Post subject: Re: Any neat ZN414 schematics out there?
PostPosted: Dec Thu 29, 2016 6:41 pm 
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Lots of nifty stuff for TRF radio experimenters at Goldmine:

http://www.goldmine-elec-products.com/p ... ber=G19076

Thanks for the link.

Rich


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 Post subject: Re: Any neat ZN414 schematics out there?
PostPosted: Mar Sat 25, 2017 12:45 am 
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and of course American radio history web page has that mag.just in case you want to read about it more..

http://www.americanradiohistory.com/Ele ... r_Page.htm


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