Archer Video Enhancer Schematic!

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Archer Video Enhancer Schematic!

Post by psyingo » Fri Sep 14, 2012 12:33 am

this is a repost from electro-music. thought it would be pertinent here as well.

Hi there.

So I traced out a schematic from an old Archer Video Enhancer/Audio Mixer device.

I kept the schematic original, didn't add any modifications; although I did change q1 and q3 to 2n5088 and q2 to 2n5087 over the original C945 and A733. 2n3904 and 2n3906 would likely work as well. Some interesting modifications would be to change the biasing resistors for q1 and q2 and maybe R7. I have not done any mods to this circuit, nor have I built it yet. I have simply traced it from the PCB.

The circuit itself is a bit like a sharpener and contrast rolled into one. When you bring VR1 down past 10% or so, you start to lose sync which is a result of the unsophisticated circuit design. VR1 is a voltage divider/level control for the whole signal path, and there is no clamping circuitry for the sync, so everything, including sync, is attenuated by VR1. An odd artifact of this circuit is when you bring VR1 down, you start to filter out everything except blue, not sure why.

I personally rather like this circuit, despite how unsophisticated it is. It will directly process composite, with the notes above.

Just like any enhancer of this sort, you will get a lot more apparent noise when you 'enhance' the signal.

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Post by nickciontea » Fri Sep 14, 2012 8:21 am

:yay: :yay: thanks for posting.

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Post by lizlarsen » Fri Sep 14, 2012 9:08 am

Nice!! :)

For LZX'ers... you could definitely use this in an in-system patch (just remove the 75R termination resistors) and probably achieve some fun lo-fi effects. :)

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Post by wcfields » Fri Sep 14, 2012 11:38 am

Good work! Excited to see some of these Archer/Radio Shack boxes disassembled and reused in some way closer to CV Controlled modules.

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Post by psyingo » Fri Sep 14, 2012 11:46 am

i would hope they wouldn't care about some crappy transistor video circuit from the 80s, but if they do, ill just modify the values a bit or soemthing.

save it while its hot.

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Post by daverj » Fri Sep 14, 2012 2:43 pm

You can't get much simpler than that circuit.

If you have one and want to have a little fun, disconnect the 1nf C1 from the emitter of Q2 and connect a 10K pot between them. That'll give you an adjustment of the enhancement.

Or do as above, but connect the wiper of the pot to the emitter of Q2, the 1nf cap to one side of the pot, and a different capacitor to the other side of the pot (with the other side of that cap going to the +12 like the 1nf). Select a larger cap (maybe .01uf or .0047uf) to enhance the mid frequencies as well as the highs, or select a smaller cap (maybe 330pf) to enhance just the noise and fine detail.

That way when the pot is in the middle you get very little enhancement and as you turn it one way or the other you enhance different ranges of frequency. A smaller pot might be better (more even range). I'm just guessing at a common value pot. Anything from 1k to 10k will probably be good.

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Post by basementcookies » Fri Apr 25, 2014 4:42 pm

What does the JP stand for?

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Awesome Thanks

Post by CFOG » Wed Jun 11, 2014 5:34 am

Oh nice! i was gonna circuit bend one of those, but maybe ill just build one and hack it that way.

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Re: Archer Video Enhancer Schematic!

Post by OutaSpaceMan » Wed Jan 29, 2020 7:08 am

Just picked up an unused example of this device..
C/w manual and original purchase receipt..!
Sadly the manual didn’t contain the schematic so this, and the hack suggestions, are much appreciated..👍
Now I’ve got to try and remember where I put the cheapo dash cam I bought and didn’t use..
Fortunately my old video recorder is to big to lose..😳👍

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