SOLVED Testing components help

[Grazza]

I am reasonably new to this and for my latest builds I have started testing components more stringently. Most of my components have come from Tayda and I am finding that a lot of the components are not within tolerances. Metal film resistors are not within 1% but seem close enough I think. However the box film capacitors from my latest order of components, which are supposed to be 5% tolerance are lucky to be within 25%, some as far out as 40%. I feel like in previous builds I tested a couple of them and they were consistent so I didnt bother to test a lot of them.

Can anyone tell me, is this normal? Are they supposed to be this far out? The tester I am using is this one below. I just recently bought a nice looking Fnirsi tester and it turned out to be rubbish so I am sending it back. Is there something else I should buy for more accurate results?

Also, what am I looking for when testing a diode?

And when matching a quad of transistors, how close is close enough.

A lot of questions there, I am sorry but would love help with this as I have put my building on hold as I am thinking I need to order more components. I alreasy spent a fortune with Tayda, should I be ordering through Mouser or digikey?

 

[KreoPensas]

I'm not an expert but I would distrust the LCR readings more than I would the batch of parts. I prefer to buy IC's from Digikey, Mouser, or Allied which is absolutely nothing against Tayda. I buy plenty of stuff there too.

 

[KreoPensas]

Regarding tolerances and circuits:

My experience is that if the values are common, the circuit is tolerant in that area. If the value is way off the wall, match it as close as possible.

 

[Grazza]

Cheers, previous batches from tayda have read pretty close to what it says on the bag so I thought the tester was accurate. Can anyone recommend a good tester?

 

[BuddytheReow]

Try recalibrating your tester.

 

[Grazza]

OK, how do i do that?

 

[jwin615]

OK, how do i do that?

With the unit off, short the 3 leads together and turn it on.
It likely came with a little bag of bits. One of which bits are 3 crimp on ends attached together. Use that or just bend 2 clipped component legs into a U and bridge 1 to 2 and 2 to 3

Also, those are pretty terrible below 50pF or so.
If measuring a low pF value and I don't want to reach for another meter, I'll usually grab a 100pF or so, measure that. Then measure the 100pf and small value cap in parallel, then deduct the first caps value.

 

[jwin615]

Also, be sure to discharge caps before measuring. New in bag isn't a big deal. But if you pull a large electro fresh off the breadboard or something, could be bad news.
I just put a small square of metal tape on mine, below the zif socket, and tap the cap before insterting.

 

[Grazza]

Great thanks guys

 

[Grazza]

Ok, just got my hands on a multimeter that can read capacitor values and it is showing readings that the capacitors should be. I recalibrated the tester and it is showing 76nf for 100nf cap whereas the multimeter is showing 101nf. Am I right to assume the DMM is more accurate and I need to bin the tester?

 

[Nostradoomus]

depends on the meter

 

[Grazza]

Its a mega expensive meter but is pretty reliable for most things, do they generally measure capacitance well?

 

[Grazza]

Sorry, it's not a super expensive meter, but it seems reliable for most things. I have just read that a good quality LCR is probably a better option though

 

[micmac]

I have a similar tester. It's not as exact as my DMM. It only gives ballpark numbers. But it's

- cheap (20 bucks)
- super easy to use
- it's pretty fast

So usually I prefer it over the DMM for pedal building. When I need precise measurements I switch to my DMM.

If you ever buy a DMM, get one with 10 Mega Ohm input impedance.

 

[micmac]

I just checked and made a few measurements. It looks like yours, the model is T-7 though. I got it maybe 2 years ago. Never calibrated it I think. Below some measurements against the DMM for comparison. They're not too far away from each other. When in doubt I'd go with what my DMM says.

Resistor 1%	DMM	T-7
2k2	2k193	2k236
560k	562k4	565k7
8k2	8k201	8k194

 

[Grazza]

Thanks for that, I will get one. I believe that my DMM has 10M input impedence. Great post thanks.

 

[Barry]

I use a Peak DCA75 for diodes and transistors, resistors I use my DMM

 

[Grazza]

Thank you, I have looked at those a few times since this little crisis of mine. They are just under $400 AUD, if I knew it was 100% the way to go I would buy one. Haven't really had much feedback on them til now.

 

[jwin615]

Believe it or not, there are supposed counterfeit TC1s. Cheaper processor used and some changes on the PCB. The version with an ATMega324 is the legit one.
I did notice, you have a red dot in the upper right of your screen. That's not typical. At first I thought this may be related to the IR reader, but it doesn't mention it at all in the "user manual" or googling.
Maybe it's a low power/battery indicator?

 

[Erik S]

I’d be willing to bet that the manufacturers of the pedals we’re cloning are not paying workers to test every resistor and capacitor before soldering it in.

I get everything I can from Tayda. I visually check the color bands and printed cap values as I install them to make sure I didn’t grab the wrong one, but I trust the components. Before I got the hang of reading the printed values I would spot check a few with a DMM to make sure I was using the right ones and I never found a problem.

Even if you find a resistor that’s out more than 1% or a cap out more than 5%, I don’t think that’s a reason not to use them. That’s probably 5x the level of precision that matters in most pedals.

There are places where measuring is important and good test gear matters, but I don’t think it’s checking all your resistors and caps.