Hey Guys.
i've just started to build my first pedal. Well, im building a Test box first.
Im following exactly the offboard wiring from Madbean and i got trouble with the DC jack.
when im using only the batery, everything works fine, i can even wire via the aligator plugs, a pcb and works 100%. When i plug a DC adapter, started a strong Hummmmmmmm! If i remove the adapter, leaving only the battery, everyting perfect!
with the adapter plugged, the true bypass is working fine. if the switch is on, again the strong Hummm!
If i remove the input guitar cable, the hum still there.
The only "wierd" thing that i can find is that the 9V adapter is sending 13V to the pedal.
Is there a correct way of wiring the positive wires to the DC jack or doesnt matter if you where u wire the battery snap (the ground is properly wired, the question is only for the 2 remaining lugs)
thanks a lot for any help
cheers
No idea on why you're getting 13v from the power supply, but for they wiring I'll try and help. The ground wire goes the the centre lug with the bolt/rivet type thing on, and the other lug in the middle goes to the positive battery snap wire. The lug is switched and will be off when a power jack is connected to save the battery power. The lug on the outer edge is the other power lug, and goes to the board.
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Quote from: Gledison on June 20, 2013, 08:43:52 PM
Hey Guys.
i've just started to build my first pedal. Well, im building a Test box first.
Im following exactly the offboard wiring from Madbean and i got trouble with the DC jack.
when im using only the batery, everything works fine, i can even wire via the aligator plugs, a pcb and works 100%. When i plug a DC adapter, started a strong Hummmmmmmm! If i remove the adapter, leaving only the battery, everyting perfect!
with the adapter plugged, the true bypass is working fine. if the switch is on, again the strong Hummm!
If i remove the input guitar cable, the hum still there.
The only "wierd" thing that i can find is that the 9V adapter is sending 13V to the pedal.
Is there a correct way of wiring the positive wires to the DC jack or doesnt matter if you where u wire the battery snap (the ground is properly wired, the question is only for the 2 remaining lugs)
thanks a lot for any help
cheers
So for the adapter, it sounds like it's gone bad on you. for the dc jack wiring, you have the ground wire, immediately to the right is the adapater wire and then lastly the battery + wire. Have a look at this http://www.madbeanpedals.com/tutorials/downloads/StandardWiring_MBP.pdf
Hey!
Thanks for helping! i got the stupid barrel jack and i changed for the "standard one" (the same described by madbean offboard wiring). My wiring are correct.Tripple check :P .
I will switch the DC adapter for other one and see how it goes.
thanks again for helping!
Hopefully it's all sorted now. I hate having to try and trouble shoot builds that don't work properly.
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Quote from: stevie1556 on June 21, 2013, 10:00:12 AM
Hopefully it's all sorted now. I hate having to try and trouble shoot builds that don't work properly.
Sent from my thumbs using Tapatalk!
Me too, I hate when I don't build it right the first time, but it's even worse when a part has gone bad on you. I've had a few adapters go belly up, and left me pulling my hair out thinking it was my build.
Could it be that you are using a positive tipped 12V power supply? It should say on the wart what the input and output should be. Just trying to cover all the bases here.
Quote from: Gledison on June 20, 2013, 08:43:52 PM
The only "wierd" thing that i can find is that the 9V adapter is sending 13V to the pedal.
UNREGULATED power supply.
Most unregulated wall wart PS will put out above its stated voltage. All that the spec means (ex. 9VDC 200mA) is that the PS will put out AT LEAST 9VDC when it is run to its maximum of 200mA. After a 200mA draw, you will see less voltage coming out.
I have several 9VDC unregulated power supplies that put out 13-16VDC when measured at the jack and/or while connect to a circuit. WATCH THOSE CAP VALUES WHEN USING THESE!!! :-\
Hi.
Jprizz: im using the negative one!
Govmnt_Lacky: yeah, is tottaly unregulated.
Do you think that this will make this strong Humm? Im still waiting the new PS to solve this mistery!
Damn it. First Build, first mistery! i guess this is one of the reasons this stuff is so adictive!! :P
cheers guys
The power supply can inject a lot of noise into the power rails of the pedal. Depending on the type of effect, that can easily come out as hum on the audio lines.
Where the noise comes from can be a bigger issue. It can be from the power supply, the wiring in your house, local ground loop in your effects and amp if they share points in the power circuit, etc.
One thing to note, the 13V on the unregulated supply is the unloaded voltage. When you power something with it, it will drop. How much it drops depends on the power supply and how much current the effect pulls. To find out where it is when loaded, you can just hook up the effect and then measure the voltage of the power supply on the board.
It's your ps, they go bad and put out more than they should. I had a phaser that would hum and I drove myself nuts trying to figure it out because it worked great with a battery.
Hey mates!
I´ve just bought an 1spot adapter and now im getting 9,3V, what i assume its ok!
But, the problem persists! I decided to build than, in another enclosure, and the same problem as in my iphone Box! a very high frequence hum, i believe a lot of dogs got mad aroung my apartment :P
What i dont understand is: using the 9V battery, everything works perfectly. I can understand that an unregulated DC adapter can bring noise to the board but not working at all as well?
cheers !
9,3V is a fine level for the voltage.
Is it a hum or a squeal? By squeal, I mean a high pitched, loud oscillation.
Hey RobA,
yes, kind of squeal. and if i put the put the gain on "11" :P i get some wierd distortion, but only playing the notes harder! just keep in mind that With batteries everything runs smoothly!!!
any tip in how to kill the bloody Squeal? :P
Could be time to post photos and a link to the schematic.
Because it works with the battery and not with either power supply, I'd suspect something in the DC jack wiring or a possible ground loop that is only introduced when the DC jack is inserted.
I will post some pictures a.s.a.p
I found something that might help you experts to solve the mistery.
I've got a old battery that is sending 6.5V. With this battery everything is working fine.
I decided to check with a new one and guess what? the same problem as i got with the adapter.
it seems that the problem is on the pcb than? :P
it seems to me that somehow is not accepting more than 7V, anything higher, it starts to crash!!!
maaaaaaan this thing is getting very interesting!!! :P
any diagnostic?
cheers
Well, that changes everything. Now you need to check all the standard stuff, voltages, solder bridges, component values, etc.
If it's got op amp gain stages, pay close attention to the parts in the feedback sections. Make sure they are the right values and that they are making contact with the PCB and there are no bridges on the pads.
Probing for audio and seeing where it starts to squeal would help too.
RobA, i have no audio probe (yet).
i've found the GGG tubescreamer IC voltage specs. Im using the tonepad layout but , here we go:
original voltage (from DC adapter=9,35V
Ic pins
1- 4,7 V (4,5V) 5- 4,7 (4,5V)
2- 4,9 V (4,5V) 6- 4,7 (4,5V)
3- 4,7 V (4,5V) 7- 4,7 (4,5V)
4- 0 V (0V) 8- 9,35 (9 V)
on brackes are the GGG measurements
It seems to me that the IC is ok.
im using 2 transistors 2N3906 (on tonepad should be 2N3904)
my measurements are:
(in brackets are the measurement for the 2N4401)
Q1 e = 1,36V (2,5V)
b= 8,72V (3V)
c= 9,35V (9V)
The same values for Q2 were obtained.
it seems that my emmiters are sending less that it should and the base is quite high!
could be only a differnce from the 2N3906 in comparison with the 2N4401 ?
so, any further help :P
cheers folks!
thanks mate!
The 2N3904's and 2N4401's are NPN transistors. The 2N3906 are PNP. They aren't interchangeable. The transistors are just being used in an emitter follower, so going from the 2N4401 to the 2N3904 won't make any difference really. Actually, you can use pretty much any NPN BJT here as long as you get the orientation of the pins right. But, you can't use PNP.
Cooooooooooool! you got it!
damn! when i bought the parts the guy told me that was equivalent! BAs"%£$%%rd!
Well, i will change and i hope will be fine.
thanks a lot for your help!!!
cheers
Can i use a 78L05 instead of the 2N3904 ?
cheers
Quote from: Gledison on June 24, 2013, 08:17:13 PM
Can i use a 78L05 instead of the 2N3904 ?
cheers
Nope. The 78L05 is a 5 volt voltage regulator. It's just in the same package as a transistor. What you need to be looking for is an NPN transistor (not a power transistor though). Some examples are 2N5088, 2N3904, BC547, BC549C, and BC550C. The BC549C and BC550C are nice because they are low noise devices. But, they certainly aren't needed in this circuit. There are lots of others that would work too. The best thing to do is check the spec sheet to make sure that the device you are considering is an NPN transistor. It should say that at the top of the spec sheet for any transistor that is. If you just type the part number into the search at Mouser or the like, they'll almost always have a spec sheet for the part.