BSIAB Troubleshoot Low Volume

Started by daleykd, October 03, 2013, 03:34:40 PM

Previous topic - Next topic

daleykd

Guys,

I've been doing my first DIY stompbox using GGG's BSIAB.  I am not doing any mods; I'm using the parts list from GGG.

After a lot of time, I finally got it to make sound (and it seems, some distortion), but the output volume is incredibly low, even with everything dimed.  Throw the switch into bypass, and BOOM, lots of volume.

I tested my voltages of my JFETs, and they all are ALMOST the same as GGG's, except for Q3 and Q5 having a gate of 0v.  (I've read many people say this is normal.)

Now, I'm using an audio probe, but I'm NOT quite sure where to test it on my circuit.  Starting at the inst. input of the PCB, I get a standard level, and I start tracing the circuit.  If I turn my amp's volume to 0 and touch the drain of Q1, I get sound out of my amp.

Can someone point me in the right direction for using the audio probe to determine where my volume drop is occurring?

TIA,
Kyle

Kipper4

It would be best if you went to the what to do if it doesnt work, debug thread and post up some more info so we can help better please.
Some of the guys especially the space cowboy will sort it out toute suite i'm sure
Ma throats as dry as an overcooked kipper.


Smoke me a Kipper. I'll be back for breakfast.

Grey Paper.
http://www.aronnelson.com/DIYFiles/up/

lungdart

http://www.generalguitargadgets.com/pdf/ggg_bsiab2_sc.pdf?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a

Follow the audio path. Sw1A -> R2 -> Q1G -> C4 -> R6/C5 -> C6/R19 -> Q3G -> C12 -> Q5G -> C9 -> C8/R7 -> R20 -> R17 -> R18 -> R21 -> output

This will show you where you are losing signal. Usually signal loss is caused by a leak into ground. Once you find where in the circuit the signal loss happens, look around where it connects to ground. Might be a short, bad component, or mistake in building the circuit.
Electronics product designer
Stomp Labs Inc
Stomplabs.com

daleykd

I'm so sorry.  I can't believe I overlooked the sticky thread.  :facepalm:

I'll read over that and do as it says, then report back.

Thanks, lungdart.  I'll also try your signal path.  (After looking at something as long as I have been, things get blurry.)

daleykd

#4
Checklist
1.What does it do, not do, and sound like?  Low volume
2.Name of the circuit?  BSIAB II
3.Source of the circuit (URL of schematic or project)?  http://www.generalguitargadgets.com/pdf/ggg_bsiab2_lo.pdf
4.Any modifications to the circuit? No
5.Any parts substitutions? N/A
6.Positive ground to negative ground conversion?  Um, no?  The black of the 9V battery goes to ground.
7.Using DIY PCB based on copper clad.

DMM: 20 DCV
Battery: 8.57V
9V: 8.53V
Post-D1: 7.85V

Q1 - D: 4.65V  S: 0.35V  G: 0V
Q2 - D: 7.85V  S: 4.65V  G: 3.72V
Q3 - D: 4.71V  S: 0.85V  G: 0V
Q4 - D: 7.85V  S: 4.72V  G: 3.72V
Q5 - D: 3.52V  S: 0.56V  G: 0V

Per lungdart's signal chain, From Sw1A to Q1G, things are at the proper levels (bypass levels).  Then, at C4, it gets overwhelmingly loud.  This is where I turn the amp's volume to 0 (off), and it still is very hearable thru the speaker.  It stays this way until Q3D, where I lose a lot of volume and possibly even pick up some ground hum (I THINK... hard to tell based on the way I'm holding the audio probe).  I might even get a bit of distortion at this point (which, I should based on the schematic).

Could it really be as simple as a bad Q3?  I have verified my pinouts.  I can attach an image of my REALLY ugly board if you need.

duck_arse

I had a slight fever

daleykd

In a way, I was hoping you wouldn't ask for this.  I'm incredibly embarrassed by the soldering job.

My goal was to get the first one to work, no matter how ugly it was, and then the second and third would look much better.

I have confirmed the paths by using my DMM.  All of them work.  I know some of the solder joints are hideous, but again, they do appear to work.

The wire 'jumper' is to fix one of my traces that fell off.  As for the Q5 leads, they aren't touching other traces.  I was testing a replacement Q5 (which wasn't the problem... so I wasted a 2N5457).



Kipper4

Man i feel good about my soldering skills now. :)
Dont worry about it. I've made a lot worse ones, Still do occasionally.
Did you check for solder bridges with the meter too.
Are you heat sinking when soldering jfets?
For future referance you can use a piece of insulation tape to hold the componant im place while you solder it in.
Top right hand corner looks a bit iffy.
Ma throats as dry as an overcooked kipper.


Smoke me a Kipper. I'll be back for breakfast.

Grey Paper.
http://www.aronnelson.com/DIYFiles/up/

daleykd

Quote from: Kipper4 on October 04, 2013, 02:08:46 PM
Man i feel good about my soldering skills now. :)
Dont worry about it. I've made a lot worse ones, Still do occasionally.
Did you check for solder bridges with the meter too.
Are you heat sinking when soldering jfets?
For future referance you can use a piece of insulation tape to hold the componant im place while you solder it in.
Top right hand corner looks a bit iffy.

First, let me say that before I was troubleshooting, it looked A LOT better.  This is what happens when you get frustrated and don't want to ruin all your components, and try to make a new PCB. :)

I'm going to show my newbness (I've been soldering for a while, but never on this level).  What is a solder bridge?  When I checked my traces, I checked from one side of a component to the other side of the next component.
No, I'm not heat sinking my JFETs.
Thanks for the recommendation on the components.  I never even thought about tape, and was quite frustrated that they didn't stay in place.
Is it iffy because the solder looks bad?  Being that it has a common ground pour, it has SEEMED to work so far.

Kipper4

Heat sinking transistor is a good idea (put an elastic band round the handles on the long nose pliers and clamp around the transistor leg you are about to solder).
A solder bridge is when you accidentally bridge the traces with solder. I'm still a noob too.
With such a good close up shot i can see solder spatter all over the board.
It just looks like the common ground is not very well soldered.
I'd also try to put a single pcb ground wire to the board. And use grounds off board from a star ground. Google it if your not sure.
I totally understand your frustration. My first project a deacy amp gave me a headache and a half.
The audio probe is a really useful tool too. I have to say it took me a while to get a handle on tracing signal paths and i still get it wrong now and again.
My set up.
Noisy cricket amp (made just for testing pedals, housed in an old 60's reel to reel speaker cab)
1/4" jack one end
croc clip on ground wire.
Signal wire is put through an old felt pen casing with a 10nf cap wired in series and the other end of the cap is soldered to a nail with the head cut off and is hotmelt glued in the narrow end of the felt tip pen case.) Bosh job done. Very ghetto but it works fine.
I wont show a pic so dont ask please. :) my only regret is i didnt make it very long.
We will get you there. I'm sure someone more knowledgable will be along soon.
Ma throats as dry as an overcooked kipper.


Smoke me a Kipper. I'll be back for breakfast.

Grey Paper.
http://www.aronnelson.com/DIYFiles/up/

pappasmurfsharem

Quote from: Kipper4 on October 04, 2013, 02:42:46 PM
Heat sinking transistor is a good idea (put an elastic band round the handles on the long nose pliers and clamp around the transistor leg you are about to solder).
A solder bridge is when you accidentally bridge the traces with solder. I'm still a noob too.
With such a good close up shot i can see solder spatter all over the board.
It just looks like the common ground is not very well soldered.
I'd also try to put a single pcb ground wire to the board. And use grounds off board from a star ground. Google it if your not sure.
I totally understand your frustration. My first project a deacy amp gave me a headache and a half.
The audio probe is a really useful tool too. I have to say it took me a while to get a handle on tracing signal paths and i still get it wrong now and again.
My set up.
Noisy cricket amp (made just for testing pedals, housed in an old 60's reel to reel speaker cab)
1/4" jack one end
croc clip on ground wire.
Signal wire is put through an old felt pen casing with a 10nf cap wired in series and the other end of the cap is soldered to a nail with the head cut off and is hotmelt glued in the narrow end of the felt tip pen case.) Bosh job done. Very ghetto but it works fine.
I wont show a pic so dont ask please. :) my only regret is i didnt make it very long.
We will get you there. I'm sure someone more knowledgable will be along soon.

I have a broken multimeter probe soldered to the output switch lug on my test box so I can either croc clip the output wire or leave it hanging and probe for the output it's very handy
"I want to build a delay, but I don't have the time."

J0K3RX

hmmmm... :-\

In the future, I would use sockets for the jfets rather than heat sinking them but if you are gonna solder them directly in then use something to dissipate the heat.

It kinda looks like you may be using lead free solder? (Please, I don't want to get into a debate about lead free solder!)

You really need to check for bridges.. try to clean the solder splatter between all connections.

You have possibly quite a few things to trouble shoot rather than just one problem..
Doesn't matter what you did to get it... If it sounds good, then it is good!

duck_arse

if you are buying your boards pre-drilled, find a new supplier with smaller drill bits. if you are drilling them yourself, you need smaller drill bits. a smaller hole will leave more copper in the doughnut, making soldering a bit easier, if not less messy.

and now we want to see your wiring of pots, etc. I rekon, if you've got some signal coming sometime, yr problem is going to be in the tone control area. if you can lift C9 (which might be 100nF or 1uF, depending on the circuit I look at) at the fet end, and try your audio probe into the free end of the cap. listen then at the wiper of the tone pot, and then at the clockwise lug of the vol pot. tell us what goes.
I had a slight fever