Electronics problems. Please help!

[Ken]

Well, today was to be a joyous occasion. I thought I'd finally completed my pedalboard. Get it all hooked up and plugged. Barely a sound is heard. I turn up my amp, and you can barely hear the guitar.


Whip out the multimeter and measure from the end of my guitar cord which goes into the pedal chain, to the very end of the cord traveling to my amp.

The measured resistance for that path was 100kOhm!

Naturally I was ticked. I took out each cable and measured its resistance. Here are my numbers (I did not subtract the resistance of the metering cables.)

Metering cables: 0.3 ohm
20' Monster Cable: 0.4ohm
Input of board to Crybaby: 0.5ohm
Crybaby to AutoWah: 2.2ohm
AutoWah to Envelope Filter: 2.5ohm
Envelope Filter to Distortion: 3.5ohm
Distortion to Flanger: 1.0ohm
Flanger to Phaser: 1.2ohm
Phaser to Digital Delay: 1.3ohm
Digital Delay to Slap Echo: 1.4ohm
Slap Echo to Compressor: 5.0ohm
Compressor to Output: 0.4ohm
10' Monster Cable: 0.4ohm

Adding these numbers obviously does not equal 100,000 (100k), and multiplying doesn't get me close either. Where in the world is so much extra resistance coming from? I find it hard to believe it's anything but the new custom connections since I've run all these effects together in this order before with no problems. I was just trying to save myself some setup hassle by localizing everything and decreasing the amount of cable, but now my guitar is literally whisper quiet!

I'm showing this information to my physics teacher tomorrow, but I am really stumped. Any help any of you electronics guys may offer will be greatly appreciated.

 

[Kent S.]

Re: Electronics problems. Please help!

Running the DC current from the meter thru your pedals isn't a great idea, infact it's a no-no. Unless you've got all true hard wired bypasses.
Unless I missread this, that sounds like what you said you did, sounds like one of the peds went south on you, or there is a grounding problem with trying to power all your pedals off something that that may not be compatible (maybe a few of the pedal want to see reversed polarity), or the is a partial short that you are missing (intermittent). If you plug straight into the amp with each cable (yes even the 6"patch cables or what have you) and you know those are fine, then the problem is somewhere else. An input or output may have fried or become a partial connection. Simply put if the cables check out (actually playing), then the problem is somewhere else, If each pedal checks out (playing) then the problem is somewhere else. If you run into problems when they are combined (especially if you are using a *one for all* power supply (read ... may not be compatible with the voltage /current /polarities of all pedals), then you know there is a problem there. Just take it one peice at a time.

 

[Ken]

Re: Electronics problems. Please help!

Wow, I didn't know that metering like that was potentially harmful...thanks for the heads up! Hopefully I didn't fry anything.

Right now my money is on the power supply. When I get home tonight I'm going to switch all the pedals over to battery operation to see if that improves things. If not, then it's time to start testing them one by one. Ugh...


Thanks so much for your help! I really appreciate having a resource like this forum for when things just aren't adding up.

 

[Kent S.]

Re: Electronics problems. Please help!

The current from the meter isn't going to fry anything, but it's still not a good idea for more than a few reasons (just don't do it), plus the pedals have input and output caps designed to BLOCK DC from getting in or out of the pedals ...so the manner in which you were testing it was, well, not conductive (no pun intended) to getting a clear answer to what was going on, sounds like the caps were partially charging, and the impedance resistors were passing some of the current. I wouldn't give stock to the reading you got in the manner in which you tested it (thru the pedals), I 'd check the cables themselves, the AC power polarities, voltage and maximum current draw (is the supply rated high enough to take the current draw). Then the input and output jacks of the units themselves. Also hit R.G.Keen's site, ... www.geofex.com and look up his audio probe, build one (you'll laugh when you see what it is), and use that plugged into an amp on low to probe the pedals to see were you are losing signal at, and yes the cap on that probe is to keep out the DC bias on the pedals from popping the amp while letting thru the audio signal.

 

[Ken]

Re: Electronics problems. Please help!

Well, every reading I gave above is cable-only. The only reading that passed through any pedals was the 100kOhm for the entire run.

How should I go about measuring the polarities, vAC and milliamps?

 

[Kent S.]

Re: Electronics problems. Please help!

Well, every reading I gave above is cable-only. The only reading that passed through any pedals was the 100kOhm for the entire run.

How should I go about measuring the polarities, vAC and milliamps?

In short, read the manual that came with your meter ... But the adaptor should tell you if the center of the barrel connector is hot or ground, the mA rating will be on it as well, the voltage is easy enough to measure, although that should be listed on it as well. The same info regarding voltage and polairty should be on your pedals, if not 9v is a safe bet (I know I can hear DUH!, right now)but the curent draw is either on the pedals or you'll have to look it up with the manufacturer, to measure it, you'll have to run them off the battery (no adaptor)and measure the current drawn from the battery, turn the controls until you find the highest number (doesn't matter if it's positive or negative, as that's just showing the curent direction, the number is waht you are concerned with here),read the manual of the meter, it should show you how to do current measurements (ie put the bloody thing inline with the battery, read the precautions, if you screw up your meter it's not my fault. Do all the pedals work okay to begin with? If so, I figure there is some type of power problem. Do they work all hooked together, but running on batteries alone? If they do, it's a power supply problem, or wiring error.

 

[Imp]

Re: Electronics problems. Please help!

just test the pedals themselves - start from the amp. plug into the box HALFWAY across the board.

if you hear the guitar as normal, that half is ok. the problem lies before it.
if not, well, you've narrowed it down a lot. look at the pedal in the middle of the 'problem' half.

it could be that the power supply you have is really struggling with all those pedals... switching to batteries will tell you a lot here

hope this helps man

tom

 

[Thames]

Re: Electronics problems. Please help!

Resistance ?!! You wont get anywhere with such results.

Guitar signal has very low current, measured in millivolts. At this low current, resistance as very little to do, but CAPACITANCE plays an major role. Guitar cable performance is measured in capacitance per foot, whereas speaker cable is measured in resistance per foot, the current being alot higher (and that's the reason why they dont need shielding).

So dont waste your time measuring resistance... the problem is elsewhere.

 

[Robert S.]

Re: Electronics problems. Please help!

Yikes, all these in depth explainations for the physics of a pedal board make my head spin.

Troubleshooting a pedal board is easy and you shouldn't need a meter. Plug your guitar into and out of each pedal first and make sure each individual pedal is working. If one is not, there is your problem.

Next plug into the first and second pedal and check for signal at the amp. Keep adding pedals one at a time until you find the problem, and then correct it.

Not all pedals plug in from the right and out from the left. My best guess is that you have a pedal plugged in backwards.