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Old 4th Jan 2016, 7:57 pm   #1
BigClick
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Question Difference between CH.1 and CH.2

Hi folks,
Apologies for another newbie question...

On the trader sheet for my first project I see what is a symbol for the chassis ground but in some cases it says CH.1 and in others it says CH.2 (see attached). can anyone explain the difference?

Also on the switch layout the switches are labeled S1, S2 etc but on one switch bank there is a "BE" see attached. I dont know what the difference is here either.

thanks
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Old 4th Jan 2016, 8:16 pm   #2
vidjoman
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Default Re: Difference between CH.1 and CH.2

Don't think we can tell from only that small bit of info. What set is it? We can then look at the circuit to see what is there.
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Old 4th Jan 2016, 9:38 pm   #3
Silicon
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Default Re: Difference between CH.1 and CH.2

Are you working on a dual channel oscilloscope?
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Old 5th Jan 2016, 12:25 am   #4
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Default Re: Difference between CH.1 and CH.2

Are there two chassis by any chance?
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Old 5th Jan 2016, 1:11 am   #5
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Default Re: Difference between CH.1 and CH.2

The set is a Regentone A.155
It looks like it's the chassis but I wonder why .1 and .2?
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Old 5th Jan 2016, 1:14 am   #6
Nicklyons2
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Default Re: Difference between CH.1 and CH.2

Could it be a stereo device and it simply means Ch2 layout is the same as Ch1; the complete circuit being shown for one channel and just the switching being shown for the second?
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Old 5th Jan 2016, 1:42 am   #7
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Default Re: Difference between CH.1 and CH.2

From the Trader circuit, Ch1 is the VHF tuner chassis and Ch2 is the main chassis. ERT doesn't distinguish between them. Be only appears on the bandswitch drawing, possibly unused contacts?
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Old 5th Jan 2016, 1:47 am   #8
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Default Re: Difference between CH.1 and CH.2

Radio chassis often have earth-tags stamped out of the chassis in the form of a tongue of metal that various components or wires are wrapped around. Theory says that "earth" is "earth" but in the real world of wiring and sheet metal of significant dimensions, resistance and impedance appear- maybe very low but possibly significant. Sometimes, it's good to separate earthing points for different parts of the circuitry- for example, earthing the power supply capacitors and oscillator/mixer section to the same point on the chassis might under some circumstances introduce an incurable background warble, so they get connected to differing points on the same chassis, hence the "CH.1" and "CH.2" designations. In other cases, such as audio amplifiers, it can be important to have a single point earth to avoid instability. Earthing layout in electronics is frequently a combination of sound theory, long practice and finally a bit of oh, , let's try putting this one here....

Sometimes in mains transformer-less ("AC/DC") sets, it could indicate that they are separated by isolation capacitors and it becomes very important for electrical safety to connect the right component to the right place!
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