Power/Wiring problem I keep having

[olejason]

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:

[neandrewthal]

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.

[olejason]

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.

[davent]

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

[neandrewthal]

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.

[olejason]

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

[galaxiex]

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) ?

[olejason]

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.

[galaxiex]

Can you post good, clear, well lit, in focus closeups, of the board (both sides), your wiring, etc.

Maybe we can spot something.

[davent]

Long as the ic's oriented correctly no worries with the socket. Does the voltage drop with the ic not on the pcb?
dave

[olejason]

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

[galaxiex]

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.

[matmosphere]

I just glanced at the layout but I think you have ic2 flipped.

[neandrewthal]

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.

[BrianS]

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  LOL. Hope you get it running soon.