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In Reply to: RE: Ok Peeps,I've been watning to show these power-supply modiules posted by Michael Samra on July 19, 2016 at 23:01:07
Those types of switchers generate tons of hash. I don't think you can filter it all or that the noise can be prevented from getting into the car's electrical system. Be sure to try this arrangement on a temporary basis first. Personally, I'd use one of the old Heathkit mobile inverters for this. They're much quieter.
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Buy Chinese. Bury freedom.
Follow Ups:
in some pics later.You may have to be a little creative and maybe use a choke and possibly a capacitance multiplier.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Switchers like those create high levels of noise that travel onto both the input and the output wiring. The input wiring is of particular concern because this path connects to other devices in the car. In addition, the input wiring can act like an transmitting antenna for the noise, and it's difficult to filter because of the DC current involved. As Tre' noted, you'll also have to deal with noise radiated directly from the device. Mu metal shielding sounds good in theory, but the supply can't be entirely enclosed due to the need for ventilation. In the end, the noise can be reduced somewhat, but not eliminated. This is why I recommended a temporary installation first, with no permanent mounting until you're sure there are no ill effects.
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Buy Chinese. Bury freedom.
Here's the thing..Back in the late 80s and early 90s,VCRs like TVS have been for years before,had gone to a switch mode power supply.The switching noise from the SMPS hasn't gotten into those circuits and with TVs and VCRs,we have RF,video,audio,and even an AGC delay line, all enclosed in a small area. This does show that a SMPS can be properly implemented to do its job but again,they were using shielding and small chokes on the main rail. This is why I think would be fine but I won't say for sure.
Notice on this VCR that the guy is working on,no longer has the switch mode supply separate with a shield.It actually part of the same board.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Edits: 07/21/16
The video S/N of a VHS VCR is so bad, any SMPS noise is insignificant.Now in the mid 1980s I worked on a broadcast quality ANALOG color corrector which used an SMPS at first. We could not get rid of the noise until we put the supply in a separate box with ferrite cores on the cables.
Much better but still saw noise on a reference video monitor. Went to a large and hot linear power supply, that fixed it.
So yes, it is a matter of degree.
That said I have used small SMPS's on both analog video and audio gear since and have gotten away with it. But you need to be careful with layout.
Edits: 07/21/16 07/21/16
So the goal is VHS audio quality? You're right, that might be possible. :-)
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Buy Chinese. Bury freedom.
Edits: 07/21/16
What about the air borne hash?
An AM radio will prove it's existence.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
I know about Blonde Lebanese hash.It looks like a pastry almost.Hehe.I'll check it with a test but you can use MU metal as an isolation shield a lot of times.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Edits: 07/20/16
"Imagine 10, 20, or 30 individuals running or riding naked in a field of wild marijuana.
It begins with a freshly showered person riding naked for hours on a clean, washed horse inside a two-meter-high "forest" of marijuana.
Afterwards, the human body and that of the horse are covered with a thick layer of resin mixed with sweat.
This produces a substance that is usually dark brown in color, which is then thoroughly scraped off the human and horse's bodies.
The mixture is subsequently pressed, molded into bars, and dried.
The "plastilin" that results from this process effectively comprises very concentrated marijuana bars."
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
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