TL072 buffer issue - no signal

[mtwtrf]

Hi, I built a buffer from Tagboard Effects on Vero square pad board and I am not getting any signal. This is my first time using this material, and it was admittedly a little tricky for me. Since it was not stripboard, I tried to make all the appropriate bridges, but still nothing. I've attached some photos. Here's a link to the stripboard layout for comparison: http://tagboardeffects.blogspot.com/2011/04/klon-buffer.html

What am I doing wrong? I'm pretty sure my continuity is checking out in the right places. I'm including a picture of the reverse side unedited, and edited to showcase the connections (I think) have continuity. Does this make sense compared to the strip board layout? You'll notice I bridged IC Pins 1 + 2 directly together, and pin 8 direct to 9v. I also misplaced the 47u capacitor so I bridged the (+) lead directly to pin 4. (And pin 5 just trails off to nowhere)

Also wondering, is the wiring correct? (In to input tip, out to output tip? Common ground to input sleeve?) I've never wired for an always-on effect. Thanks for looking.

JL

*edit*
Voltages:

1 - wildly oscillating beta 4.6 - 5.8
2 - similar to 1
3 - 0.38
4 - 0

5 - 9.33
6 - 0.65
7 - 1.09
8 - 1.09

Are pins 1&2 acting strange because I have put a jumper between the pins instead of in connecting them to the next row on the board?

[GibsonGM]

http://www.diystompboxes.com/smfforum/index.php?topic=29816.0


"You'll notice I bridged IC Pins 1 + 2 directly together, and pin 8 direct to 9v. I also misplaced the 47u capacitor so I bridged the (+) lead directly to pin 4. (And pin 5 just trails off to nowhere)..."


No comment. 

[anchovie]

I also misplaced the 47u capacitor so I bridged the (+) lead directly to pin 4.

*CLANG!*

By doing that, you've sent the V/2 voltage reference that biases the input signal straight to ground. The 47u is intended to get rid of AC noise in that reference, so if you don't have the cap you should leave the connection open and risk a noisy buffer, or replace with another electrolytic cap if you have one (anything 10u or higher should be fine).

[mtwtrf]

Well I redid the board - tried to create the same board following a schematic I found from a different site for reference (that had a different stripboard lay out) to no great success.

The fact of the matter is, I'm so green, but this process really helped me get a better handle on schematics following alongside the build. Prior to this I have only built off of nice, sleek purchased PCBs. I think I followed the current flow to a couple end points but got mixed up with the IC, as I don't really have a grasp of what that does. While this was a good exercise, I'm going to wait to troubleshoot them later. I think a big problem is that I don't have a matching schematic for this layout - the one I was looking at seemed too different (and also had a strip board layout, but I wanted to see if I could overcome my initial failure). Luckily I ordered some proper strip board so I hopefully won't make the same mistake the third time around... and as I learn more I can go and correct one or both of the buffers I attempted on square pad.

Thanks for the replies.

JL

[dwmorrin]

Is there anything connected to pins 3, 6, or 7?
Looking at the underside- I can't see any connections to those pins.
That would explain it.

[arma61]

Hi

I've noticed this.. you say in the thread title "TL072", though the link you linked ( ) says (bottom left) "IC is TL071", 72 is a dual opamp, 71 is a single opamp, so pins are not the same, you said "...and pin 8 direct to 9v" this is ok for 072 not 071, that's pin 7.


Forget about that, I've just opened the link in a small window, didn't see the 2nd board!! forgive me!! 

Good luck... and have fun!!

Ciao

[GibsonGM]

Keep going, MTW...this is how you learn. I'm glad to hear you're working WITH the actual schematic. Feel free to try to route the parts YOURSELF!  That's how I've always done it, with great success.  But the first few builds  can be iffy, if you don't have a handle on what to keep away from other parts, etc.    So keep them simple for a while, like this, and have fun with it!    You'll get better exponentially if you keep on...

[avianoguitarist]

Make it a habit to breadboard your circuits before committing them to perf, vero or etched PCBs.
You would have been able to debug this project before soldering.
Also, since you mention you're green at this--DO NOT deviate from the layout.
Your deviations were the cause of the issues.  Also, know your components and what they do--read datasheets on ICs. Jumpering pins you know nothing about is disastrous...as you found out.

You'll get there--just follow schems and layouts to the letter.

[sde]

Hi,

Nice your sardine-can-like design.

As suggested by dwmorrin, try to connect your input to pin 3 (1IN+ = the positive input of the first opamp).
Also, while the 2nd opamp is not used, you should connect pin 5 and 6 to ground (2IN+ an 2IN-) and leave pin 7 (2OUT) floating.

[MrStab]

try flipping the layout horizontally in Paint or something, and compare it to the underside of your board (as i'm guessing you've checked the top enough).
maybe pointless, but when i was starting out, i found that examining stuff from different perspectives could help a lot.