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Re testing the components, note that the readings can be affected by other components in the circuit so when measured values don't match what you expect you may need to un-solder one end from the board to measure accurately.

Here's what the coloured bands mean
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Discussion Starter · #642 ·
Thankyou Bob. That is the exact chart I'll need if there's still no sparks after repairing the stuff already identified.

For now I'll satisfy myself with their apparent consistency and hope they don't become a potential issue.
 

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FWIW, I studied electronics half a century ago (in the awkward period after they stopped teaching about vacuum tubes and before they started teaching about integrated circuits) but haven't really done much for the last couple of decades because I didn't really have anywhere to work. Last winter's project was re-organizing the basement workshop I inherited from my Dad a couple of decades ago and I decided one of the benches was going to be for electronics. When I was putting some components that I've had for a long time away I decided to spot check some of the resistors to make sure I was putting them in the right drawers and the off readings led me to learning that carbon composite resistors can change value over time so I spent a bunch of time measuring several thousand of them and ended up throwing out a hundred or so bad ones.
When I was doing electronics all the time I could read resistor values pretty easily but lately not so much so when I started testing the resistors I put that chart up on the computer's screen and consulted it a lot. By the end I hardly glanced at it ;-)

Re the parts you circled in red: Like Brink, my first thought would be that they are capacitors but with them being folded over onto the mounting tabs of the semiconductor devices like that thermistors (temperature dependent resistors) to compensate for component temperature makes sense and Andy's page that Brink linked does mention something like that.
BTW: Those semiconductor devices could be transistors, SCRs, Triacs or even a couple of other types but I'd need to see the writing on them and look up what they are.

Re measuring capacitors: When I was in school that was done with a rather complex and expensive device called a capacitance bridge but these days a lot of multimeters can do that. When the season for working in the garden and garage ends and I go back to the basement shop I have a big box of capacitors that need to be tested & sorted like I did with the resistors.
Note that capacitors must be measured out of circuit because even the traces on the circuit board can affect their readings, let alone other parts of the circuit.
 

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Discussion Starter · #644 ·
A capacitor [condenser} as used in points ignition can be tested by briefly flashing it to a battery - lead to positive and body to ground. If you then bend the lead back to 1/4 inch from the body you should get a spark between the terminal and the body proving the capacitor is charging and discharging.

I don't know how these would be powered up though so you're probably right.

I have my basic meter inside at the moment as I can read resistances easier on a non auto ranging meter.

But my more expensive meter may have a suitable setting. Strangely, I only bought that one for one thing - audible continuity.
 

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Ignition condensers are a special type of capacitor. Also, that test just tells you that it is taking and holding charge (the most basic functions of a capacitor), not what the capacitance value is. In electronics capacitors can be used in different ways and sometimes the value is pretty important.

The new meter I bought this year has full auto ranging but it also tells you what the value of the component being measured actually is as opposed to the ones that you have to set to a range and then figure out what the reading means). In the pic below the resistor is supposed to be 220Ω but the meter says it is actually 279.6Ω (after the pic it went into the bin). Note that it shows "Ω" above the 9; If the value was KΩ or MΩ it would say so instead of you having to figure it out from the range the meter is set to. You can also set it to a specific range before measuring if needed/desired so that you don't have to wait for it to decide on the correct range and switch to it, although it does that faster than any of my other meters measure the value anyway.
I tried measuring a couple of capacitors when i got it go make sure it works and it seemed to be OK but I haven't used that function much yet.
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Anyway, that's probably enough of me hijacking your thread to tell you about my shop....
 

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Discussion Starter · #646 ·
Nah, you're pretty close to the topic.

Re the old school capacitor test. A fair assessment of the health of the condenser could be made by the level of snap of the spark.

I had my first bike when I was 15. A CD175 bought not running.

I had ne experience and no one to help me so it went to a workshop - where it sat for literally months, poked at occasionally but undiagnosed so unrepaired.

I brought {pushed} it home.

That condenser test came from a book on motor mechanics dating back to the year dot. It diagnosed the problem and the part was replaced with resultant running bike. I still have that book.

I've never taken a bike to anyone except for tyres since.

And our four wheelers only three times. Two of those I still ended up rerepairing their repair. Anderson automatics did a great job of rebuilding our commodores trimatic though.
 

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Automatic transmissions are a mystery to me that i don't even want to understand! LOL
 

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Discussion Starter · #648 ·
Me too. We've had few cars with autos. To own it generally we need to be able to fix it.

When I was about 17 I had a top of the range 1971 toyota crown deluxe with everything including an auto trans and a dreadful engine factory fitted.

The trans slipped, bucked and carried on and being largely ignorant of such matters took it to a local garage for a service and band adjustment. It was still carrying on when collected.

I put it over our pit and observed no sign of work with bolt heads etc. still [email protected] encrusted.

My local library had the manual for this car.

The pan not only had to come off to adjust one set of bands {the other set were accessable from outside - though still [email protected]} it had to come off to even drain the thing, let alone change the screen.

I did it myself. It was never great but it was greatly improved.

The engine blew up on a fruit picking trip. I sold the car for $65 and hitch hiked home.
 

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That's a funny story although i'm sure it wasn't at the time! I can't understand how these so called "repair shop" employees/managers can sleep at night or look themselves in the mirror when they charge you money for a "repair" they didn't even do??? So unscrupulous!
 

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Re the old school capacitor test. A fair assessment of the health of the condenser could be made by the level of snap of the spark.
<<<
That condenser test came from a book on motor mechanics dating back to the year dot. It diagnosed the problem and the part was replaced with resultant running bike. I still have that book.
Oh, I don't doubt that it is a good enough test for ignition condensers, and I wish someone had told me to check the one in my Dnepr that way (I did eventually figure it out but only after a lot of stalling and hard starting).

But for caps used in a circuit like this (found randomly on the internet) it wouldn't even come close

(Understanding Schematics - Technical Articles)
 

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Discussion Starter · #651 ·
my understanding of these things is less than rudimentary.

my understanding works like this. Diode - anti backflow valve {I worked in irrigation}, transister - 3 pin switching relay. Resister, means to reduce flow of power etc. I don't understand electronics. But if you can identify a fault, identify and obtain the needed part many things can be repaired by the bloody minded. :p

Many years ago my son was interested in electronics. I bought him a fairly fancy metal detector in kit form. Fairly intricate, many parts and neither of us were game to tackle it. I've ended up with it and think I should tackle it at some point soonish. I can't remember it's features but only that it has some discriminatory functions.
 

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One definition of a capacitor is 2 conductors separated by an insulator.
For DC when power is applied to a cap it charges up and the current stops flowing so it is basically an open circuit. But for AC it has to charge alternately as the voltage polarity reverses, which allows some of the charge to pass from one side to the other (complicated physics that I no longer remember how to explain) so it acts as an impedance (the AC version o resistance) and the impedance decreases as frequency increases.

Inductors (coils) are the opposite; They pass DC like a plain wire would but for AC they have impedance which increases as frequency increases.

When you put a coil and a capacitor together the impedance of one increases while the impedance of the other decreases and there is a frequency where the combined impedance of the 2 is highest or lowest (depending on whether in series or parallel), called the resonant frequency. Such circuits are used to make oscillators, radio tuners &c.

I'll bet your metal detector kit has at least a couple of tuned circuits like that.
 

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Impedence = resistance?

Have just ordered 20 IN4007 resisters for the princely sum of $3.85 posted. Should get them next week.
I think yes...but Sidecar Bob......??? Maybe a conversion factor??

"Impedance is the property of the material to oppose current in ac circuit and resistance is the property of the material to oppose current in dc circuit. Resistance is given by ohm's law R=v/I. impedance is a measurement which combines resistance and inductive reactance and capacitive reactance."
 

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I generally assume a capacitor in a circuit is the correct value as I'm not designing the circuit. Then I apply my trusty old Simpson analog meter on OHMS setting, first one polarity connection and then reverse the polarity. On a good capacitor I expect to see the needle rise at a decelerating rate and stop, then do the same on the reverse polarity connection, actual values ignored. If it fails to move the needle or pegs it I try a different OHM meter setting and if still undesired display, its trash. If its trash and the value is not printed on the cap I try to research the correct component, otherwise the circuit is moved closer to the waste can. Real basic but I've saved quite a few circuits that way over my life, more industrial electrical (motor starting caps) or auto than any sophisticated electronics though. There is a lot of basic electrical system troubleshooting (as opposed to electronics) that can be done with 2 or 4 120v light bulbs in series connection. Some of my most admired old time mentors in the electrical construction and industrial world didn't even have a meter in their tool box. Those days are gone though, until the apocalypse.
:D I do own several decent digital meters, but they can be deceptive by detecting very very small voltages and currents because they don't "load" the circuit. Again, I'm not speaking of electronics, but "working electricity".
 
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Discussion Starter · #656 ·
Rich, I just checked the capacitors by the method you gave on the 2000K scale. Both polarities produced a climb to max reading and then went beyond the 2000K scale. I guess that means they're OK.
 

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Impedence = resistance?
I think yes...but Sidecar Bob......??? Maybe a conversion factor??

"Impedance is the property of the material to oppose current in ac circuit and resistance is the property of the material to oppose current in dc circuit. Resistance is given by ohm's law R=v/I. impedance is a measurement which combines resistance and inductive reactance and capacitive reactance."
I was giving the simplified explanation. Impedance is normally specified in ohms the same as resistance is and most people can understand that resistance is the opposition to current flow in DC
Not really a conversion factor per se. As I said before, impedance depends on the inductor or capacitor and the frequency of the voltage.
Note that in a purely resistive load impedance is equal to resistance.

Anyway, the only place most people encounter impedance is for speakers. In the old days it was fairly important that the impedance of the speaker and the output impedance of the amplifier match and if they didn't the could could be distorted most amps had output transformers with 8Ω impedance so most speakers had a nominal impedance of 8Ω (as a speaker designer getting the impedance vs frequency graph as close to a straight line as possible was one of my goals for higher end models).
Then they learned to make amps that don't need output transformers and their outputs were compatible with 4Ω, 8Ω, 16Ω or whatever the speakers were and they eventually figured out that if the speakers were 4Ω instead of 8Ω the amp could produce more power from the same supply voltage.
Explanation: The peak to peak (AC) audio output voltage cannot exceed the DC supply voltage without flattening off the peaks of the waveforms (called "clipping"), a particularly audible form of distortion).

Have just ordered 20 IN4007 resisters for the princely sum of $3.85 posted. Should get them next week.
I hope not. 1N4007s are supposed to be diodes.... ;-)

I think I paid about $2 CAD for 20pcs the last time I bought 1N series diodes on eBay but prices have gone up since then. The best price I can find for 20pcs axial lead 1N4007 today is $2.96 CAD/$3.21 AUD so that's not a terrible price
(I did find SMD 1n4007s for a bit less but you don't want to get into soldering them if you don't have to).

Rich, I just checked the capacitors by the method you gave on the 2000K scale. Both polarities produced a climb to max reading and then went beyond the 2000K scale. I guess that means they're OK.
An ohmmeter works by passing a small DC current through the resistor under test and measuring the voltage across a known resistor that is in series with it.
When you connect a capacitor to an ohmmeter it charges up and when you reverse the capacitor it discharges through the meter, then charges up with the new polarity. Basically, the initial low resistance reading (the resistance scale of an analogue meter usually reads from left to right, the opposite direction to the voltage and current scales).
Depending on the meter and the capacitor value you might be able to determine if the cap is accepting charge that way but it won't tell you anything about a cap in the pico or nano farad range and my 100KΩ/V analogue meter (that recently died after being my good meter for over 30 years) would barely kick the needle even on caps in the 10-100 microfarad range (most digital ones won't tell you anything that way either).
 

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Discussion Starter · #658 ·
Yeah, I thought diodes while my hands typed resisters. I do this...

I'm guessing impedence relates to recharge time in the case of a capacitor?
 

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Sort of. There's some physics involved related to charge rates, the size of the plates and the dielectric constant of what is between the plates and a few other factors that I mostly understand but it has been so long since I needed to know the details that I'd have to look up how to explain it. And it also depends on the frequency of the signal applied.
For everyday purposes the easy way to remember the relationship between frequency and impedance is to think of it this way:
DC is zero hertz (cycles per second). A capacitor is an open circuit for DC (at least once it has finished charging), which is infinitely high impedance/resistance so its impedance is higher at low frequencies and decreases as frequency increases.
A coil is basically just a bunch of wire so at DC (zero Hz) the impedance/resistance is equal to the DC resistance of the wire (when we measure an ignition coil with an ohmmeter this is what we are looking at - it takes a lot of turns of very fine wire to make up thousands of ohms in the secondary winding) so its impedance is the lowest at low frequencies and increases as frequency increases.
 
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