Both pots on my pedal do nothing. (Update!)

RjM · January 30, 2005, 11:13:39 PM

I don't know why, but they just do nothing. Doesn't matter if they're all the way up or all the way down. I wired my pedal wrong the other day, and my pots lit up inside of them... (electricity) Can pots be fried, or otherwise be damaged by shorts?

See the last three posts for the update. I guess the pots were fine after all, and I am using the wrong imput and output jacks, apparently called 1/4" mono NC tips.

R.G. · January 30, 2005, 11:24:57 PM

QuoteI wired my pedal wrong the other day, and my pots lit up inside of them... (electricity) Can pots be fried, or otherwise be damaged by shorts?

Yes, they can. My parents-in-law have a solid rock **chimney** that was damaged by electricity - lighting, but the principle is the same.

The diagnosis is simple - take out your digital multimeter and measure the resistance between the center lug and the outer lugs and between the outer lugs. If the center lug is open to either outer lug, it's fried.

Don't have a multimeter? Get one. They're available under $10, less than another box and stomp switch.

Umm... generally batteries won't put out enough power to fry pots. What are you powering your effects with??

petemoore · January 30, 2005, 11:35:53 PM

I had a 9v battery smoked pot, lit up like a cigarette cherry !!!

Outlaws · January 30, 2005, 11:38:46 PM

One of my pots won't do anything either. I don't get it. It never lighted up or gave any indication.

petemoore · January 31, 2005, 02:06:47 AM

New pots work.
Most all of the time, don't remem getting a bad new one, heard it happens though...
You measure the resistance like RG says if you want to test your pot. You'll have to figure...or just pull the pot from the circuit to do a conclusive test of your pots ability to V/R between lugs 2,3 and 2,1.
The measured resistance between lugs 1 and 3 is the value of the pot.
Generally when a pot doesn't work, it's a wiring error.

RjM · January 31, 2005, 12:47:40 PM

I have a multimeter, but I'm never sure what settings I should use, or what readings I should look for. What will it read if it is 'open'? It has various AC and DC voltages, and can also test diodes. I triple-checked the wiring for the pots, and it's definately right. I'll just have to get new ones. I've also had a bit of trouble biasing the transistor. I set my multimeter to 20v, touch the black probe to gound, and the red one to the drain of the MPF102 transistor. I get readings, but I'm not sure what kind of readings I'm suppost to be looking for. I'm suppost to adjust the trimpot so that the power drain of the FET is 4.5v, but all readings are to the right of the period, so it doesn't seem like i'm even close to having it adjusted correctly.

petemoore · January 31, 2005, 01:04:47 PM

Can you *link a schematic of what it is?
Did you socket the transistor ?
"Funny voltages that are a decimal point off the mark...
Wrong resistor value [try checking 'em in Cct. see what you can figure]
cold solder
misoriented transistor leads

RjM · January 31, 2005, 01:13:27 PM

It's the spakleboost I'm building. I've double checked, the leads of the transistor is correct, I do have a 2.4m resistor instead of the 2.2 you're supppost to have, and insead of 2k7, I have 3k9. Didn't socket the transistor. I'm not quite sure what a cold solder is. I use a power supply for my pedals.

http://www.diystompboxes.com/sboxforum/viewtopic.php?t=28818

Link to the schematic.

j0shua · January 31, 2005, 01:13:38 PM

HMMMM STRANGE CASE , ARE YOU SHURE YOU ARE USING CORRECT POTS? , CHECK FOR COLD SOLDER .. AND IF THE CAP FRY THAT'S MEAN ( SHORT CIRCUIT ) .....

PUT THE SCHEMATIC HERE TO KNOW BETTER

petemoore · January 31, 2005, 02:29:41 PM

Quote from: RjMIt's the spakleboost I'm building. I've double checked, the leads of the transistor is correct, I do have a 2.4m resistor instead of the 2.2 you're supppost to have, and insead of 2k7, I have 3k9. Didn't socket the transistor. I'm not quite sure what a cold solder is. I use a power supply for my pedals.

http://www.diystompboxes.com/sboxforum/viewtopic.php?t=28818

Link to the schematic.

Cold solder is like non conductive joint.
3k9 is off, but I cant say if that would cause bias to be off so much, doubtful it 'does' more than decrease headroom a little bit. 2m4 should be fine, won't pull input too close to ground, anything over 1meg shouldn't cause a real problem there.
Socketting the Q is a good idea, for pinout, and also trying other Jfets of the same type, because they vary alot. I use sockets alot for Q's.
ANY way you might be able to take some R readings like I say in Circtuit, disallow 'low' readings [lower than what the R looks like] or calculate other path math [why that reading looks like that with R in cct compared to alone] or... start pulling R's and testing them.
A good idea is to test every single R on the board just before installing it.
A schematic LOOKs like what I have 'till I find the difference in my board wiring and the schematic...look at and count all leads at each node.
Look at the nodes. count how many and what connections go to each one. This is a good practice for pre-intensive stuff like reading R's in circuit and testing continuity of solder joints to insure no cold solders exist.
Leaving lead above the board [next to the resistor body] makes it easier to contact the DMM probe to it. I got tired of that...try to hold it on a blob on the bottom WHILE trying to find then touch the 'other side' of a joint atop the board....

petemoore · January 31, 2005, 02:31:33 PM

Be sure all grounds are connected. including the jack sleeves and cct ground...anything with the ground symbol 'attached' on the schem. simply not having a ground may let some signal through, the pots wont' work.

RjM · February 01, 2005, 08:28:27 PM

I just found something out... the jacks I've been using are both mono jacks! They have 3 soldering lugs though, and I've wired everything per the schematic. I unplugged the DC power supply from the sparkleboost, and there was no change in sound at all! I don't think that the FET is getting any power. Alright, bear with me. I'll try to explain what I did for wiring.

Where the battery clip is, imagine the battery clip not there and just a wire from the DC jack to the imput jack. Should I have that wire, and if I need it, should I connect it to the ground lug since it is a mono jack? I don't care if I don't have the feature of having it off with the input cord unplugged. Would it work then if I wired it to the ground lug?

Look at the jack at the very right. It has four lugs, and just imagine the fourth lug not there. It has the same setup for the tip connection with the smaller piece of metal contacting the tip connection.

Oh yeah.... I think I get it. Insead of having one lug for signal and two for ground, the mono jack with three lugs has two for signal and one for ground...

the_badcliff · February 01, 2005, 09:16:39 PM

thats a switchable mono jack that you've got, and it has what is called an "NC Tip". I forget what the NC stands for, but you won't use it in this case. You just want to solder the input wire to the lug that connects to the regular tip, and connect the ground to the sleeve, which is in the middle.

If you are not using a battery clip then that wire should be left out altogether. The green wire is the ground and the red wire is +9V. Make sure your polarity is correct from your power supply. I don't know if this will get your circuit running just right, but its a start.

RjM · February 01, 2005, 10:00:16 PM

Alright, let me get this straight. I should connect the second lug to the third lug, on both input and output jacks? I used the same NC tip mono jack for both input and output. The polarities are definately correct.

Outlaws · February 01, 2005, 10:14:18 PM

Quote from: RjMAlright, let me get this straight. I should connect the second lug to the third lug, on both input and output jacks? I used the same NC tip mono jack for both input and output. The polarities are definately correct.

Simple unintelligent answer warning!!!

I don't know what this jack you discovered is, but just stick a 1/4" cable in it and connect something to a lug that is touching the lower half of the metal jack for ground and something to the lug touching the tip for the signal.

RjM · February 01, 2005, 10:37:47 PM

Quote from: Outlaws
Quote from: RjMAlright, let me get this straight. I should connect the second lug to the third lug, on both input and output jacks? I used the same NC tip mono jack for both input and output. The polarities are definately correct.

Simple unintelligent answer warning!!!

I don't know what this jack you discovered is, but just stick a 1/4" cable in it and connect something to a lug that is touching the lower half of the metal jack for ground and something to the lug touching the tip for the signal.

Alright... so I just connect the signal lugs to the ground lugs. Simple! heheh... time to finally have a finished sparkleboost.

RjM · February 02, 2005, 01:23:06 PM

Alright... I just found something dissapointing out. When I turn the effect off is when I get sound. When I turn it on, it gets no sound. When the DC jack is plugged in, and the effect is off, there is a light humming. If I turn it on, the humming increases a tiny bit. What are some causes of a non-working circuit? Bad caps? Everything is wired correctly, I've triple checked all wiring and soldering. This is so annoying, having all the parts for an effect, but having them be pretty much useless since it doesn't work. Man.......

Dragonfly · February 02, 2005, 01:39:42 PM

Quote from: RjMWhat are some causes of a non-working circuit? Bad caps? Everything is wired correctly, I've triple checked all wiring and soldering. This is so annoying, having all the parts for an effect, but having them be pretty much useless since it doesn't work. Man.......

there are so many possibilities for what can cause a circuit to go wrong....bad voltages, bad grounds, solder bridges, etc.

read R.G.'s "a sticky is needed" post for a cuple hints at the info we might need to aid in the debugging process....

also...check the debugging page at this website....

often times, its the pinout of the fet/transistor...are you 100% positive its oriented properly?

andy

RjM · February 02, 2005, 01:45:15 PM

I at least know that I have the correct pinout for that. I had to switch the gate and source legs since the layout you gave me was made for the NTE, which is DGS, and the MPF I used is origionally DSG. I'll eventually fix this thing... I'll measure the voltages when I get home.

Dragonfly · February 02, 2005, 01:53:01 PM

Quote from: RjMI at least know that I have the correct pinout for that. I had to switch the gate and source legs since the layout you gave me was made for the NTE, which is DGS, and the MPF I used is origionally DSG. I'll eventually fix this thing... I'll measure the voltages when I get home.

cool....we'll "keep with it" till you get it going

debugging can be frustrating, but you eventually end up learning a lot more about the cicuit than you would have if it "fired right up" !

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Both pots on my pedal do nothing. (Update!)