A quick question re:Multimetres and wiring.

[nDR01d]

OK everyone, I just want to be sure here so that's why I'm asking the question - If I set my MM to 200 Ohms and then poke and prod around the wires, I should be getting a small reading, say 0.3. And this means I've connected the wires correctly. So when I get a reading of 1 this means there is no connection and I have to resolder that wire? Thanks in advance. =D

[stan]

if you get a reading of 1 you have exceeded 200 ohms

select a higher option

you are correct in that a small or zero reading should indicate continuity between the two probes

[nDR01d]

Thanks Stan. Always best to double check :)

[stan]

1 can also mean an open circuit: no conduction/connection at all

[nDR01d]

OK, so I have tested and retested all the wires and at the moment, I have narrowed it down to the 0.47uf capacitor(?). I took it out completely and put my clips on it and got nothing across either lead. Does this mean I need to replace it, or is this normal? BTW, if I have to replace it, is there anything better than 0.47uf or is this the 'standard'?

[wokkaboy]

Hey Ndroid,
maybe check another capacitor see if you get a reading. Try a different multimeter setting too.
There is no standard rating capacitor it all comes down to the personal taste of the sound you like.
Try experimenting with a lower uf capacitor and see what sound you prefer

[nDR01d]

Thanks Wokka, I tried out a green cap - 2A473J was printed on it that came with a TL-1A I ordered. I think that means it was also a 0.047uF. But that had a reading on the 20M setting of 0.38. So I guess my multimeter is working and the other cap is not. I tried all the settings for Ohms too. Looks like it's time to order 1 or 2 Orange Drops from Adam! ;)

[wokkaboy]

hey NDroid, yeah those conversion figures sound right.
Yeah order some orange drop caps are good.
There's a few more to choose from at Realtone
http://www.realparts.com.au/electronics/capacitors.html

I'm yet to try the treble bleed circuit are
http://www.realparts.com.au/electronics/capacitors/klein-treble-bleed-capacitor-and-resistor-mod.html

They are designed to work better when the volume is lower

[Rabbitz]

Unless you really know what you are looking for a digital multimeter (DMM) set to measure resistance will tell you very little about a capacitor. Even then it will tell you very little.

Without going into extremely deep detail a capacitor is a bit like a rechargeable battery, it will store a charge and release it when the voltage feeding it drops below a certain point.

So when you connect your ohm-meter (DMM) across the capacitor the voltage applied by the DMM will start to charge the capacitor. Now, an ohm-meter is used to measure resistance, thus the ohm-meter is looking to compare a known voltage that it supplies with the voltage it receives back after it passes through the resistance. The voltage difference (or voltage drop) is used to calculate how much resistance there was.

Back to our capacitor, as the capacitor charges it "takes some of the electrons out of the circuit" which the ohm-meter will see as voltage drop. So as the capacitor charges the meter will show a change of resistance up until the capacitor is charged then it will show an open circuit - the capacitor is now blocking the DC voltage from flowing. This is all very fast and a digital meter may well miss it all and show just an O/C. A mechanical meter may show a bounce of the needle.

Some (well a few) DMM's actually have a capacitance meter. This can then tell you a) what the value of the capacitor is, and b) whether the capacitor is actually working.

So why does it make a connection in the guitar? Inside the guitar the current flow is a form of alternating current, thus the signal will flow through the capacitor as it is alternately charging and discharging depending on the state (+ve or -ve) of the signal due to the modulation from the strings.

I hope that was meaningful.

[nDR01d]

Thanks Rabbitz. I'm still going to buy a couple, just to be on the safe side.

[DrNomis_44]

OK everyone, I just want to be sure here so that's why I'm asking the question - If I set my MM to 200 Ohms and then poke and prod around the wires, I should be getting a small reading, say 0.3. And this means I've connected the wires correctly. So when I get a reading of 1 this means there is no connection and I have to resolder that wire? Thanks in advance. =D



Usually, if you're measuring resistance on a Digital multimeter set to 200 Ohms and you're measuring an open-circuit it will display OL on it's LCD screen, a reading of 1,or something like 0001 will mean a resistance of 1 Ohm.


Readings of less than 1 Ohm will display as 0000.

[keloooe]

I personally use an auto-range MM, you just select the type of measurement and it automatically sets the range and gives you the unit it is measuring in as well, I like it!

[DrNomis_44]

I personally use an auto-range MM, you just select the type of measurement and it automatically sets the range and gives you the unit it is measuring in as well, I like it!


I'm a bit more old-school with my multimeters, you have to manually change the ranges with the ones I have, I've been looking into buying a replacement for one of my digital multimeters that can measure Capacitance as well as Inductance and Frequency.

When I'm working on an occasional pedal build and I'm trying to find an elusive fault that I can't find with a multimeter, I use one of my other pieces of test equipment called an Oscilloscope, usually in conjunction with a Signal Generator, they are a bit more technical.

[sulistbu]

Hi nDro1d, check if your meter has capacitance function and use it to verify your caps. Unfortunately setting your meter on resistance is not effective way to check any caps as previously mention by Rabbitz.

Budi

[sulistbu]

I'm a bit more old-school with my multimeters, you have to manually change the ranges with the ones I have, I've been looking into buying a replacement for one of my digital multimeters that can measure Capacitance as well as Inductance and Frequency.

When I'm working on an occasional pedal build and I'm trying to find an elusive fault that I can't find with a multimeter, I use one of my other pieces of test equipment called an Oscilloscope, usually in conjunction with a Signal Generator, they are a bit more technical.

Hi Dr, Element14 has this DMM, and a friend of mine recently purchase it for his study/apprentice.
Its quite good for money, I've compared it with my Fluke 177, in term of basic function and measurement (Vdc/Vac, Resistance, Capacitance, Temp, Freq ) it is very good.

http://au.element14.com/tenma/72-7735/multimeter-digital-hand-held-3999/dp/7430590?MER=MER-BPR-4PPM-SP-TM-MM

Budi

[DrNomis_44]

When you try to use a digital multimeter to test a capacitor, initially the multimeter may show a low resistance reading, then the reading will increase till the multimeter shows DC, this is because a capacitor is essentially an open-circuit as far as DC is concerned, when you measure resistance with a multimeter you are measuring pure resistance to DC (direct current), capacitors do exhibit resistance but it is resistance to AC (alternating current), AC resistance is totally different to DC resistance and is frequency dependent, this is basically how the capacitors in the tone controls of a guitar work to control how bright or dull the guitar sounds.


At very low frequencies, the AC resistance that a capacitor presents to them is very high, almost like an open circuit, now, as the frequency increases the AC resistance will become less and less and the capacitor will let more of the signal through it, the tone control pot gives us a way of controlling how much of the signal gets affected by the tone capacitor.


Apologies if I'm sounding a bit technical here.