Output/sound issues on a Boiling Point build

[Ambugaton]

Hey Everyone,

New to the forum and pretty new to pedal building as well. This is only my 3rd build and have a few problems/questions that hopefully are not too annoying.

Problem is that I am only getting output when I strum very hard and even then it is very farty and intermittent.

I double checked my veroboard for bridges and any potential cold solder joints and found no problems.

I put together a quick audio probe and have traced the signal all the way to pin#3 of the IC and everything is great up until that point. From there the signal goes to pin#5 and that is where the problem starts. I swapped out the IC for another IC that I think should be compatible (TL072ACP) and although the output was a little more consistent it was still really flubby and crackly with some loss of sound.

The IC is mounted on sockets and all connections were reflowed to ensure good connections.

Any thoughts?

Attached photo of the layout I used and a schematic (didn't really reference it while building since I am still learning them)

[Ambugaton]

Correction: I get sound on Pin#3 but nothing on Pin#1 so that is where I have followed the signal. Does that simply mean the R4558P needs to be replaced? It appears to me that the only reason the signal wouldn't continue on to Pin#1 would be internal of the IC?

[PRR]

Welcome.

If the IC is not biased at reasonable DC values, it will not work except on extreme signals.

Top of this page, "Debugging", read and report. Let's see what DC is on pins 1 2 3 first.

[Ambugaton]

IC1
P1: 9.2VDC
P2: 8.8VDC
P3: 9.2VDC
P4: 0.0VDC
P5: 9.3VDC
P6: 9.2VDC
P7: 9.2VDC
P8: 9.2VDC

Q1:
C: 9.38VDC
B: 5.3VDC
E: 8VDC

Q2:
C: 9.3VDC
B: 9.3VDC
E: 6.1VDC

D1:
A: 9.2VDC
K: 8.8VDC

D2:
A: 8VDC
K: 9.2VDC

D3:
A: 8.4VDC
K: 8VDC

D4:
A: 8.8VDC

D5 & D6 (LEDs in parallel)
9.2VDC / 7.6VDC

[GibsonGM]

Welcome, Amb, and I would suggest you go back over your board VERY carefully...make SURE every cut is made, completely.   

Everywhere that's noted as "VR" on the schematic should be about 4.5V (most of your IC pins etc should be near this)!  So either a component is in the wrong place, or there's a short from + to VR or something like that. 

Also, the emitter of Q1 needs to be very near zero volts, so I suspect something is also shorted with respect to that! 

Sometimes if you find the source of this problem, the rest of the voltages will fall in line too....

[anotherjim]

10k, R17 in the schematic, which is IC pin4 to 2nd row (as Level pot lug 1). It's acting like that resistor is missing/not connected or very high value.

[duck_arse]

Ambugaton - just in case you've done a funny mirrored build [it does happen], can you post photos of what you have built, pleeze?

and welcome.

[Ambugaton]

Thanks for all the suggestions everyone. Yeah I quickly realized that I should not be getting 9V on the IC pins after comparing to voltage readings on similar circuits.

I will go through everything and double check all component values and joints and report back.

I am wondering if I overheated Q1 and caused it to push through the full 9V? Good excuse to read about how a transistor works I guess.

[thermionix]

As suggested above, R16 and R17 need to be the same resistance.  10K is specified here but it would work if they were both 22K for example.  The voltage readings you posted suggest a high likelihood that R17 is a higher resistance than R16, although a wiring error is also possible.  But you have a good place to look first.  Maybe you have a 100K and a 10K, or a 10K and a 1K, easy mistake to make because just one band is a different color, and sometimes yellow looks like orange, or orange looks like red, etc.

[Ambugaton]

Just verified all R values and everything is good there. I did just realize that the 1k resistors are specified as CC (assuming that's carbon comp?) But would that throw things off? I wouldn't think so.

Still tracing through the schematic and verifying again. Have no experience testing caps but they charge up to 25kohm with meter leads, switched they discharge and charge back up as well.

Still looking

[Ambugaton]

Pics...reminder only 3rd build but will accept anything constructive.

[thermionix]

I don't see much similarity between your board and the layout you said you followed.

CC likely does mean carbon comp, but that's not necessary and won't affect voltages.

[duck_arse]

this one, maybe?

[Ambugaton]

Yes sorry I had posted the wrong layout

[Ambugaton]

So running a razorblade down each track of the veroboard didn't improve anything significantly... although I am now getting 7.6VDC on Pin 2 of the IC for some reason. Everything else is the same as previous readings.

[Ambugaton]

Reflowed all the solder joints on the board and get new readings:

IC1
P1: 4.7V
P2: 4.1V
P3: 4.0V
P4: 0V
P5: 9.3V
P6: 7.1V
P7: 2.9V
P8: 2.9V

Even more confused now and also realize that the readings are different depending on the switch settings between diodes and the different caps. Which I guess is to be expected.

Q1
C: 9.3V
B: 2.3V
E: 3.2V

Q2
C: 9.3V
B: 9.3V
E: 8.2V

Feel like that transistor Q2 is the problem... maybe a short between the collector and base?

Still no sound. LED lights up and the true bypass has no problems...

[thermionix]

Sure seems like you have a short between C and B of Q2.  Possible that the transistor itself is shorted, but I think much more likely that is on the board.  Vero can be tricky like that.  You have the usual things like solder bits and component leads, but also little fragments of copper from drilling out the cuts.  I know you said you ran a blade between tracks, but get a loupe or magnifying glass and really inspect every square mm.

I don't think the switch settings should change any DC voltages.  So you might have multiple issues goin on here.

[Slowpoke101]

A quick question: What transistors are you using?
Also, is there any chance that you can post a few more pictures of the component side with better lighting and different angles. Some of the parts shown on your current photo are in shadow or hidden by larger components.

Cheers.

[GibsonGM]

Sometimes you have to keep it as simple as possible.   When you see 2.9v at pin 8, which is power and should be ~9v, right there you KNOW you have a short or some other big issue at the power rail.   So you look only at that, from where the battery snap is to the board and on down the line.
First you make sure the battery isn't 2.9V, of course (ha ha).

So, 9V goes to the board top left.  As mentioned, you have the collector of Q1 there, and farther over the IC gets power to pin 9 directly from that row.

I would get my DMM, set to continuity, and see if there is continuity between C and B of Q1 - the short Thermionix suggests.   If it beeps, and you CANNOT find any solder bridge or other path, remove the C leg of the transistor and see if the IC then has the 9V on pin 8. 

As for pin 5 having 9V (??), I can't see how that's possible unless maybe you're counting pins backwards and have reversed the gnd and +?   Just a guess.

I always try to fix the power rails first if there's a problem; the other things often fall into line after that.

[duck_arse]

I think if we point out that the IC pins read 1-4 down the left side, then 5-8 in an anticlockwise direction up the right hand side, that the V+ is on the correct pin. that still leaves 5, 6 and 7 with bad voltages.

can you - power off - pull the IC out the socket, repower and measure the voltages on the socket pins (in the correcter order), please? and while you are there, what is the voltage at the junction of R17//R16//C11? your R12 appears to be not 510k - any other subs we should know about?