[ICOM] icom 706 MK2

[Adrian]

Incorrect, see;

https://www.allaboutcircuits.com/textbook/direct-current/chpt-5/simple-series-circuits/

This is basic knowledge ;


  Series Circuits and the Application of Ohm’s Law

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      What is the Total Resistance and Voltage of a Series Circuit?

In a series circuit, all components are connected end-to-end to form a 
single path for current flow. The total resistance in a series circuit 
is equal to the sum of the individual resistors, and the total voltage 
drop is equal to the sum of the individual voltage drops across those 
resistors.

In this introduction toseries resistance circuits 
<https://www.allaboutcircuits.com/textbook/direct-current/chpt-5/what-are-series-and-parallel-circuits/>, 
we will explain these three key principles you should understand:

  * *Current:*The current is the same through each component in a series
    circuit
  * *Resistance:*The total resistance of a series circuit is equal to
    the sum of the individual resistances.
  * *Voltage:*The totalvoltage drop
    <https://www.allaboutcircuits.com/technical-articles/what-is-a-voltage-drop-in-an-electric-circuit/>in
    a series circuit equals the sum of the individual voltage drops.

We’ll examine thesethree principles using the series circuit 
<https://www.allaboutcircuits.com/textbook/reference/chpt-1/series-circuit-rules/>consisting 
of three resistors and a single battery, as illustrated in Figure 1.

Series circuit with a battery and three resistors


          /*Figure 1.*Series circuit with a battery and three resistors./


      Current in a Series Circuit

In a series circuit, the same amount of current flows through each 
component in the circuit. This is because there is only one path for the 
current flow. Since electric charge flows through conductors like 
marbles in a tube, the rate of flow (marble speed) at any point in the 
circuit (tube) at any specific point in time must be equal.

An important caveat toOhm’s law 
<https://www.allaboutcircuits.com/textbook/direct-current/chpt-2/voltage-current-resistance-relate/>is 
that all quantities (voltage, current, resistance, and power) must 
relate to each other in terms of the same two points in a circuit. 
Before we examine the more complex series circuit in Figure 1, let’s 
examine this concept for a single resistor circuit.


        Using Ohm’s Law in a Single Resistor Circuit

For this initial analysis, we will evaluate the current and voltage for 
the single resistor circuit in Figure 2.

Series circuit with a battery and a single resistor.


On 11/4/24 17:48, Facility 406 wrote:
>> This is the best place to test. Measuring current at two places in a 
>> series circuit is of little benefit, as the current must be the same, 
>> following accepted electrical theory.
>
> I would guess, in a perfect conductor with no breaks or changes.
>
> Due to the numerous bad connections within the cable, current can 
> change at each one, due to heating, corrosion, arcing, loose 
> connections, bad alloys, bad plating, fuse issues, insulation in 
> crimps, broken/missing wire strands, et cetera.
>
> There would be a total draw, but current at the fuse input, for 
> example, may be a few amps, and with six failure points per fuse/clip 
> alone, per side, may only be providing a few hundred mA down the cable 
> to the radio, and, with entirely different issues between +, and -.  
> 3A draw at the supply doesn't mean the radio is getting the roughly 3A 
> it's known to require at idle.
>
> The corroded, arcing, loose, charred power connector may be drawing 
> 3-4A from the supply, and providing barely enough power for the 706 
> series "relay click", or worse, chattering, which is always scary for 
> a radio turned off, and not being touched, and no change between a 
> good power supply, and fully charged battery.
>
> "Hmm....  Must be something in the radio, it's getting power, and 
> drawing a few amps, but it makes funny noises, and won't turn on. 
> Power supply checks good with other equipment, 13.8V even at 20-30A, 
> yeah, must be the radio!"
>
> I've had areas within the factory cord be so bad, the relay click is 
> heard when applying power, but the radio cuts out just trying to turn 
> on.  If/when it does turn on, various failures, at various powers, 
> depending on how the power cable was handled between uses, or the 
> extent of failure conditions occurring during previous use and 
> storage.  But, in the end, yes, a total current, indicating something 
> is happening, but not what, where, how, to what extent, or, if equal, 
> reasonable, or expected.
>
> Sometimes the issues were easy to find.  Charred metal, faint hissing 
> from arcing, hot spots, the loud snap of a cracking fuse from excess 
> heat due to bad clips, or poor fuse element connections at the caps, 
> hot insulation smells, burning metal smells, or wires falling out of 
> crimps
>
> Testing the radio internally could be interesting, but drawing out the 
> cable, fuses, and connector, I get 16 known, and 2 more potential 
> failure points, before the power cord is even connected to the radio. 
> Once connected, most were known to occur, sometimes several at once.
>
> The cables were known bad, new, out of the box, seriously, just 
> outright trash, and got worse with actual use, both mechanically, and 
> electrically.  It was a big deal at the time, lots of posts in the 
> forums about it.  I had to change everything from the PCB inside, to 
> the power supply just to use my radio when new, the cable was erratic 
> in a mostly static desktop installation, and completely useless when 
> mobile.  Ten, twenty, or more, years of use and abuse later, assume 
> far, far worse, than, known bad, out of the box.
>
> Aside from a common trace corrosion issue due to a rubber pad with 
> high acid content resting on the main PCB, or exceptionally filthy 
> user conditions where the faceplate/head connections get covered in 
> scum, causing erratic operation, or failure to turn on, I don't recall 
> having heard of an actual radio issue, other than comments of a very 
> warm regulator in the head or a sluggish screen at very cold 
> temperatures.
>
> Kurt
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