Testing Electronics in TL-1 kit

[rokitrik]

Do any of you electronics gurus have a process where you test all electronics (pickups, volume pots, switches, etc.) prior to beginning assembly to ensure everything is in good working order?

[fender3x]

I do...

Mostly with an ohms meter. I check the pickups to make sure that each coil gives a resistance reading that it should. I test all the pots to make sure that the total resistance is right. I also check them at "5" to confirm that the taper is audio or linear (I don't trust what is stamped on the case or wafer) and that they all show about the same reading at "5." Since pots of, say 500K, can vary by over 100K, I also check to see that they are at least close to each other. I don't usually do this with new pots, but I have occasionally run a signal through them and listened for scratchiness.

I test all the switches to make sure they are working properly with the ohms meter. In this case I am just testing for continuity...that connections are open or closed as they are supposed to be (1=not conneted, ~0= continuity).

If I use any simple resistors, I test them. I did not used to have a meter that would test caps, but I do now, so I test them as well. I admit that I do this not so much to see if the resister is faulty, but more to make sure I have the right one ;-)

Once everything is connected, I clip a lead onto the ring of the jack and test to see that all the pots, switches, shielding and the strings show as continuous.

On my last project and on the one I am working on now, I have assembled the wiring harness on a template. Once the pickups are installed, I can test the wiring harness before putting it in the bass. This was VERY useful on the last project, an ES style bass. On these you have to shove the whole wiring harness through the f-hole, so you want to get it right. As I was testing the tone control, I realized they were basically not rolling off any treble. I got some advice from Weirdbits about changing my cap values, and was able to do that before putting the harness in the bass. Also, while I was testing on that bass, I pulled the shaft out of one of the pots...and was happy to have that happen during testing rather than when in the bass!

I am testing paint and finishes right now... The more experience I get the more I test everything I can.

[McCreed]

Not much I could add to what fender3x said other than I could not live without my Digital Multi-Meter (DMM for short).
A multi will give you resistance, capacitance, voltage, continuity etc. Mine will even do temperature with the special probe.

I use it constantly for all sorts of guitar work. Mine has an audible alarm for continuity testing which I find very handy.

A decent one is not that expensive (especially if you consider how much we all spend on guitars/pedals/amps ) and having one is simply invaluable.

[fender3x]

My multimeter is not as fancy as McCreed's. The "fancy" one cost me less than $20. It will measure inductance (which is useful for pickups), capacitance and resistance. That's all you need for what I wrote above. Search for a multimeter with the model name "4070L." Cheapest one I could find that measures capacitance. They are marketed under different brands (read that cheap Chinese)...interestingly all with the same model number. I have also seen 4070D...don't know what the difference is, but mine has worked impressively well.

I also have a few really cheap ones (I don't think I have ever paid much more than $10). These won't measure capacitance or inductance, but work just fine for resistance and testing continuity. Also they are great for testing batteries and LOW voltage. Don't use one of these on any real voltage!

I don't know how people lived before these devices were cheap and plentiful ;-)

[rokitrik]

I do...

f3x,

Thank you for your detailed response! Very helpful. I have a good multi-meter (see attached) that I can use to run the tests you mention. I'll give it a try and post other questions here if I get stuck.

Rick

[rokitrik]

Not much I could add to what fender3x said other than I could not live without my Digital Multi-Meter (DMM for short).
A multi will give you resistance, capacitance, voltage, continuity etc. Mine will even do temperature with the special probe.

I use it constantly for all sorts of guitar work. Mine has an audible alarm for continuity testing which I find very handy.

A decent one is not that expensive (especially if you consider how much we all spend on guitars/pedals/amps ) and having one is simply invaluable.

Thanks McCreed. My DMM tests continuity with an alarm as well. It does the rest of the tests too. I'm going to dig in and learn as much as I can on how to run the tests you gents recommend. Appreciate your input!

Rick

[rokitrik]

My multimeter is not as fancy as McCreed's. The "fancy" one cost me less than $20. It will measure inductance (which is useful for pickups), capacitance and resistance. That's all you need for what I wrote above. Search for a multimeter with the model name "4070L." Cheapest one I could find that measures capacitance. They are marketed under different brands (read that cheap Chinese)...interestingly all with the same model number. I have also seen 4070D...don't know what the difference is, but mine has worked impressively well.

I also have a few really cheap ones (I don't think I have ever paid much more than $10). These won't measure capacitance or inductance, but work just fine for resistance and testing continuity. Also they are great for testing batteries and LOW voltage. Don't use one of these on any real voltage!

I don't know how people lived before these devices were cheap and plentiful ;-)

Looks like I need the 4070L you recommend to test inductance in order to test the pickups. Thanks again f3x!

[McCreed]

Based on the photo you posted, it doesn't have continuity or inductance capabilities.
Also, I've never seen a "cheap" DMM that can measure inductance. The only devices I know of that will measure inductance (L) are an oscilloscope and signal generator.
My understanding is (and it is a tentative grasp at best) that a typical DMM does not have the capacity to generate appropriate signal frequencies as part of the L measuring process and are expensive bits of kit to make.

[rokitrik]

Based on the photo you posted, it doesn't have continuity or inductance capabilities.
Also, I've never seen a "cheap" DMM that can measure inductance. The only devices I know of that will measure inductance (L) are an oscilloscope and signal generator.
My understanding is (and it is a tentative grasp at best) that a typical DMM does not have the capacity to generate appropriate signal frequencies as part of the L measuring process and are expensive bits of kit to make.

McCreed, according to my DMM manual a continuity test can be performed, see first attachment. It cannot perform inductance tests but the 4070L advertises it does per the second attachment (note that it tests for H not L.) I agree that an oscilloscope and signal generator are optimum -- but out of the question for me really.

Maybe the 4070L DMM does not give a fully accurate reading or like you say, won't achieve appropriate signal frequency. To be honest, I doubt I would get that advanced in my testing. I guess I'm looking for simple tests that I can perform to avoid problems before I install the electronics and also a means to learn more about guitar electronics theory.

Curiosity killed that kitty, so I've got to watch my paws.

Thanks for following up, my friend.

Rick

[McCreed]

Looks to me that the 4070L DMM is all you need for doing what most of us do here.

I can't attest to the inductance, but I'd be sceptical. The other functions are more important for guitar wiring work IMO.
And just to clarify - "L" means inductance; and inductance is measured in units called Henrys (H).