I'm sure this has been answered plenty of times but I'm not sure what to search for to find an answer. Here is the issue:
1) 9v battery is plugged into breadboard, at this point I'll get a reading of 7.5-9v on the multimeter
2) As soon as my PCB is plugged into the breadboard, V+ going to positive and Ground going to negative, my reading will drop to 0-1v and no sound is produced. Reading from the ground on the battery to the V+ pad on the board also shows the extremely low voltage.
Is this a grounding issue? I've managed to fix it a couple of time by resoldering all my wires and cleaning everything up but I'd like to know what the actual problem could be.
One other question, I have a few PCB's with the standard +V, G, I, O layout at the bottom but they will also have pads for +9v and GND near the top of the PCB. Are these just optional for hooking up the 9v adapter jack? I should only be running power to one pad, right?
The current PCB I'm having issues with is the Grind Customs Helvete, if that helps. Here is the layout:
(http://www.grindcustomsfx.com/wp-content/uploads/2016/01/pcb-helvete.jpg)
It sounds to me like you might have a short on your board. Try measuring the resistance between 9v and ground on the board with your multimeter.
The +9V pad on top is the same as the V+ below and the GND up top is the same as the G on the bottom. By the same I mean the counterparts are connected together. You could run power to both but the second one would accomplish nothing because it is already connected to the first.
They are on the top and bottom because you are meant to run power and ground to the top 2 and the bottom ones are there to chain to your stomp switch, but of course you could make these connections however you want.
Thanks for your time neandrewthal. The resistance measurement between those two points is right at 15k. I'm not real sure what I should be looking for with the measurement. I checked a few other circuits I'm working on and they were significantly higher but also varied quite a bit.
Do you know the battery is good? A shot battery could read ok with no load but add a load and it's sucked dry.
dave
Quote from: olejason on July 30, 2016, 02:10:07 AM
Thanks for your time neandrewthal. The resistance measurement between those two points is right at 15k. I'm not real sure what I should be looking for with the measurement. I checked a few other circuits I'm working on and they were significantly higher but also varied quite a bit.
A short would be much less than 15k. Now that we know that its 15k it shouldnt be loading the battery down that much so Id go with Daves suggestion.
I went ahead and swapped the battery out just to be sure that wasn't the problem. With a fresh battery it reads ~8.5v off the breadboard before I plug in the PCB. Once plugged in it drops to around 1.5v and I don't get any sound at all. I'm not sure what to try next other than resoldering everything which will be difficult with board mounted pots. Everything looks okay but I know that can be deceiving.
I don't know if this helps or is even relevant. If I place an LED in the breadboard it will light up if either the PCB 9v or Ground lead is connected but if both are connected the LED no longer lights up. This also applies to the PCB itself. If I disconnect the PCB Ground from the breadboard, then place the LED in the positive pad on the board and then run a ground lead from the breadboard it will light up. But if the PCB is also grounded it will not light up.
Thanks for your help guys
Gotta be a short somewhere.
Does the battery get warm (hot) if you leave it plugged in for a minute or so?
Any parts on the PCB getting warm (hot) ?
The battery seems to remain room temperature even after plugged in for 5+ minutes. I don't feel anything getting hot on the board either. I've made a bit of "progress" though. At this point the voltage drops around 2v when the PCB is plugged in... so it stays around 6.5v-7v. The big TL074 IC seems like it may be the problem. If I fidget with it I can hear crackles and pops coming through the amp. There are times that it will squeal or sound like its self oscillating if I slowly insert it into the socket. I have voltage reading for all the legs of the IC except 11 which reads zero. Also I don't think this is an issue but my socket is soldered in backwards (notch facing the wrong way) but I have the IC situated correctly in relation to the PCB.
Can you post good, clear, well lit, in focus closeups, of the board (both sides), your wiring, etc.
Maybe we can spot something.
Long as the ic's oriented correctly no worries with the socket. Does the voltage drop with the ic not on the pcb?
dave
Thanks guys, here are some pictures. I tilted the pots as best I could to get shots of the underside of the board. The voltage does indeed drop when each IC is inserted. Here are measurements:
Battery into breadboard, no load: 7.62v
PCB plugged in, no IC's: 7.42v
Only 4558 (8 pin) IC plugged in: 6.85v
Both IC's plugged in: 5.78v
(http://i.imgur.com/oN1byOb.jpg)
(http://i.imgur.com/KJMedpN.jpg)
(http://i.imgur.com/7lOg918.jpg)
(http://i.imgur.com/kDcWIuC.jpg)
(http://i.imgur.com/FW0MWxE.jpg)
Ok, looks good so far.
In your first post you say you are using a breadboard for in/out and power.
Can you please show us those connections? Good shot of the overall setup?
Edit; just one thing.... are you SURE ic 2 is installed correctly?
Cant really tell from the pic.
I just glanced at the layout but I think you have ic2 flipped.
Basically, what they just said. We can`t see for sure but it looks like the TL074 is flipped.
It depends on what markings it has. We can see it has a dot, which marks the top in the absence of a notch. If the other end has a notch then the notch takes precedence and the IC is oriented correctly. No notch on the other end then its backwards. Simply based on a gut feeling and the orientation of the text I bet there is probably a notch though.
I looked at the build doc and from what it shows the IC is in backwards unless the screen mask is different. Not trying to beat a dead horse here just wanted to give you some words of encouragement. If it is backwards don't feel bad about it. Everyone on here makes mistakes like this so just forget it and push forward. I had a Tusk sitting on my bench for a long long time. Couldn't get it to work after several tries so I just put it in the non working pile. Last week I did a redirect and found I had the stereo jack wired wrong. After rewiring it wow it worked. I haven't build as many pedals as a lot of the guys but I think I'm over 60 now and I shouldn't be making those kind of mistakes. S--- happens :o LOL. Hope you get it running soon.
Agreed, that kinda stuff happens to everybody. I know it's happened to me before as well. Definitely don't get discouraged though, this is a fun hobby, the more you build the smoother things will start going. It might help to build a testing rig like the one Brian just posted a tutorial for. If you plan on sticking with this it's definitely worth dropping ten bucks into a testing rig, makes life much easier in the end.
Ya, I've done everything from inserting an I/C backwards, to wiring up power leads backwards, jacks installed wrong etc.
It happens, we're not perfect, and we certainly weren't born knowing this stuff.
Biggest thing for me, is to not work tired/distracted or hungry.
The other thing is to not get cocky.
The following happens when I'm any of the above.....
"I've built dozens of pedals!"
"I know what I'm doing!"
"I couldn't have made a mistake!"
Yes, I'm guilty of all those.... it's a humbling experience.
The other thing that happens is, looking at something and not realizing that it is indeed, installed backwards....
... for whatever reason, you just don't "see" it.
"i put that in there.... It's gotta be right!"
Ha! It don't gotta be anything....
Thanks for the words of encouragement everyone, I've managed to not get too frustrated with this one. I tinker for awhile and then take a break. I don't mind the troubleshooting as long as I feel like I'm making a bit of progress here and there ;D
The TL074 IC does have a notch, sorry I should have noticed it was cropped out in those pictures. I wasn't sure if the dot or notch took precedence so I tried the IC both ways just to be sure. Below is a better picture of the IC & component side of the board and a picture of how I have everything breadboarded. The red lead connected to ground is my input/output jacks. None of the wires in the middle rows are connected to the PCB. If I disconnect power and ground to the PCB I do get a guitar signal through the amp so the wiring appears to be okay.
(http://i.imgur.com/lPJKSzr.jpg)
(http://i.imgur.com/iBvi4sc.jpg)
Quote from: olejason on July 31, 2016, 11:50:40 PM
................. I wasn't sure if the dot or notch took precedence so I tried the IC both ways just to be sure. ...........
If the TL074 was installed backwards and powered up, it's a given that it fried.
Do you have a spare?
Oh wow, I definitely fried it then. Unfortunately I don't have a spare but I'll order one now. I don't recall how the IC was oriented when I first applied power but it very well could have been wrong at that point. Would a bad IC explain all the weird oscillation noises and stuff when I jiggle it?
Quote from: olejason on August 01, 2016, 12:25:27 AM
........... Would a bad IC explain all the weird oscillation noises and stuff when I jiggle it?
Very likely.
Pm'ing your address and I will send one to you tomorrow in the mail if you would like. I have an extra one you can have.
Thank you Brian that is very kind of you, I went ahead and ordered a few earlier though since I needed some other parts as well. They should be here this week and I'll update the thread... hopefully this will solve the mystery :) Thanks again to everyone who has offered assistance.
I received the replacement chips today but unfortunately I still don't get any audio when power is supplied to the PCB. I was very careful to have both IC's seated in the sockets before connecting the battery for the first time. Is there anything else you'd recommend trying? I'm not real sure where to go from here. I'm getting power throughout the circuit but I don't really know what kind of values I should be looking for. If I turn the amp up quite a bit I can hear a little hiss coming through and it is affected by turning the pots. Thanks all, I appreciate your help.
(http://i.imgur.com/89WHKqf.jpg)
I'm sure someone's mentioned but i haven't gone back through, an audio probe to trace the guitar signal through the circuit to pinpoint where exactly it disappears.
http://www.diystompboxes.com/pedals/debug.html
dave
Thanks! The audio probe is helping. I actually had a transistor with a wrong pinout in Q3. Now that is sorted and I traced to IC1 and can still hear the clipped signal going through D1, D2, D3 up to C8 but then I lose it. It also seems to be draining the battery rather quickly, maybe I should use an adapter for power for now? It's late so I'll resume tomorrow.
Bizarrely enough, the complete circuit passed signal for a moment after I changed the transistor. I thought "Hey it's fixed" and went about hooking up the output to my amp. Then it didn't work ;D
Reflowing the solder pads often helps. It looks like you have a few points there that could do with a bit more solder too.
It works! Hooking up an adapter to the breadboard seemed to do the final trick. My battery was still reading around 8v but I guess the circuit was dropping it too far to power the IC's. Someone mentioned that could be an issue a few posts back.
Thanks to everyone for all the help, setting up an audio probe will make all of this troubleshooting much easier in the future.
Have you tried a brand new battery here?? Your last post you were measuring 7.62v unloaded. That seems unusually low to me. I throw out my 9 volts if they have less than 8.8 volts. A new 9 volt should read closer to 9.5 volts. You have to take into account also how much current your circuit is going to draw.. One reason I don't bother using batteries in the pedals I build.
doh! Didn't see page 2! Good to see you got this working