CMATMOD Brownie (BSIAB II) Low Volume

[duck_arse]

what make and model is the meter you are using, please?

looking at the BIASB II from ggg circuit dia - the "supply line" is the positive rail, the V+, the line connecting the tops of R4, R11, R16 and C11. between there and ground, you should have vrr near 18V w/ the big supply, and 9V w/ the smaller supply.

on that circuit, Q5 gate connects to ground thru R14, 82k. with black on ground and red on gate, you should show 82k (or whatever your variant circuit has there). similar, Q3 connects gate to ground thru R19, 500k pot. at one extreme, that should read near 500k, at the other 0R. as neither gate shows a connection to "supply", there should be no sort of sensible resistance reading between gate and supply, it might show a counting or an overload.

[if either/any of the jfet gates doesn't have a DC path to ground, ie a resistor, the gate will wander as it likes, usually following leakage thru the cap, if there is any. sometimes the cap starts out leaking enough to 'sound right', then tails off into mis/bad bias and splut/spit.]

[Slight Return]

I'm using a Cen-Tech multimeter from Harbor Freight. Got it for free. Not sure of the quality but I can't imagine it would be great.

My caps from Stewmac came in today. Whatever they are, they look identical to the caps that were on the Brownie. I replaced that .0022uF cap with a .001uF, but it was green, looked skinnier and taller, and well...I put a .001uF cap in from Stewmac that looks identical to the other caps. Not sure if that should make any difference. Both caps I used were rated for 100v.

My Engineer Solder Sucker came in today. And I am blown away at how good it is. I ended up taking the pots out, and using the soldering iron pushed against the terminals on the back of the board, put the sucker down on the top of the board and pushed, and then sucked the solder out.

I got all the holes for the transistors completely cleaned out. No remnants of solder or clipped transistor legs. Then I soldered the sockets in. That proved to be a little challenging. If I turned the board over the solder them, they'd just fall out. So I just held the socket down with one finger on top of the board, then quickly used some solder from tinning my iron to touch the terminal on the back of the board, and hold that one leg down.

Then I'd solder the other two legs in the right way, and eventually the last leg:

Heating up the through-hole first, until it's hot enough for the solder to flow onto it. I think I might have had some bad joints earlier as a result of not doing this consistently or very well. Inadvertently I might've had a couple joints where I merely transferred solder from the tip of the iron to the joint, rather than getting the joint hot enough to have solder flow throughout it.

I am not convinced that I'm out of the woods yet. Have had way too many close calls with this thing.

But for at least 5 minutes of plugging it in after cleaning out all the holes and soldering the sockets in, it seems to be working well. All the transistors except for one of the original MPF102's are in sockets now. I used a pair of round nose pliers to bend the legs to fit. Is that proper procedure?

The Drain leg of Q5 is reading out at 4.5v, right where I left the bias with the trim pot. Again....at least for the first couple minutes of playing. I'm almost scared to keep going! So many times now it seemed great and then just stopped working. Seems to be the pattern.

@ duck

Man. I am gonna have a time with the BSIAB II. I'm struggling pretty mightily to follow what you're talking about, and I have the schematic for the BSIAB II opened on my other computer monitor as I'm typing this! Looks like hieroglyphics to me, although I watched a few videos last night on how to read schematics. Gonna take a bit for it to click, I'm sure. Big help that you mentioned Q5 Gate goes to ground through R14...that's helped me with understanding a bit of how to read schematics. I'm a *rank* beginner but I'm doing my best to learn.

For now I'm gonna demo the pedal and see if it holds up. I just plugged into my 18v power supply and it's working okay with the sockets in. I did the best job I could to get the sockets in, although a couple went in crooked. That was before I came up with that makeshift method for soldering them in straight. I would love to know if there's an "official" way to solder them in straight and clean. i.e., making sure they don't move or fall out when you flip the board over the solder from the other side.

I would love to take some measurements soon. I will say, however, that my Brownie does seem to be different from the BSIAB II, somehow. I counted the number of capacitors and resistors on the BSIAB II, and the Brownie I have has more capacitors and more resistors, something like several more of each. I am not sure how identical the boards are for the two of them, although I would assume they are pretty close. I've heard that the Brownie is a licensed, direct clone of the BSIAB II that uses the GGG board, so I found it odd that my Brownie has more caps and resistors than are listed in the schematic/bill of materials for the GGG BSIAB II.



Thanks again guys for all the help. I really appreciate it. And that description of why it could be doing what it's doing (any of the JFET gates not having a DC path to ground -- i.e. a resistor) was very helpful. It's a lot to take in being a newbie but I feel just this little project alone, and all the advice here, has taught me a lot.

I am not confident that this pedal will continue working. Given what's happened before. A bit paranoid now.

But it's working much better than last night after sucking all the old solder out and resoldering new sockets in. I'm very happy with the solder sucker and I figured the best way to go over the joints would be to redo them from scratch....get all that old solder out and put some fresh solder in, and pay very close attention to how I'm doing it.

[Slight Return]

Cut out again. Same as always...works great and then stopped. Took maybe 20 minutes of playing this time.

@ duck

"can I request a few numbers? with the power off, and the meter to Ohms, can you give us the resistance reading from the gate of Q5 to ground, and from the gate of Q5 to the supply line? and just for fun, the resistance from the gate of Q3 to ground, with the gain pot at each extreme of rotation."

Q5 Gate to ground = 82k.

From what I could tell, the supply line is basically the 9v adapter jack that I'm plugging the power cord into. I can't tell which is + or -, but holding the black probe on Ground, and using the red probe to test the tabs on the 9v adapter...one of them does read out at 18.55v with the 18v power supply plugged in.

Q3 Gate to ground reads 511k with the Gain knob all the way up. It reads 0 with the Gain knob all the way down.

[duck_arse]

Slight - that is good on a few counts. the resistance figures clear the gate bias to some degree, they are what would be expected. and, it seems you are coming to grips with using your meter!

your one-pin soldering of the sockets is the approved method. one leg works for most solderings of that sort, as long as you rework your first tack-joint so it is up to par before moving on.

but we still no closer to the fault/fix.

[Slight Return]

Kit came in today. Got it done. Took quite a while.

It doesn't work -__- Most immediate thing I realize wrong is that Q3 Gate has no reading at all. 0v. And if I touch it with the probe while the pedal is on, it goes to a buzzing noise. Not sure what that means.

I thought the socket might be bad. After 15 minutes of using the solder sucker to no avail to get the socket out, I had to clip it. It was extremely difficult to get at it with the board wired up and installed, and I didn't leave an incredible length of wire to flip it over. It ended up ripping the entire top of through-hole out of the PCB on one leg. F***!

Again...checked all the transistors against the reference voltages. Everything was in spec expect Q3...on the Gate of Q3 to ground, with the amp and pedal on, I was getting 0v and also a buzzing sound.

Issue I'm having is almost zero volume, and no gain.

I resoldered the transistor in. Funnily enough, the socket was probably fine. Where the through-hole was completely ripped out, I am still getting around 4.7v (Drain leg of Q3).

But still 0v and buzzing on Gate of Q3. Although the reference voltage is 0.3v on Q3 Gate, so....doesn't seem too crazy. The buzzing was concerning. I have not audio probed the circuit yet.

I am just about ready to quit here...or I would be if I didn't know that problems with first time builds are really common. Just hard not to be frustrated when I'm over 190 bucks in the hole and just have two non-functioning pedals, and for the life of me I cannot figure out what's wrong with either of them.

But after I found the pedal didn't work, I was like OK...let's test it....but when I accidentally tore the through-hole off the PCB for a few seconds I felt about ready to throw a brick through the window. Or my BSIAB II, which is about as functional as a brick at the moment.

I spent all day today working on building the BSIAB II from the kit, and paid meticulous attention to the wiring everywhere. I soldered everything in absolutely as well as I could, even using my new tip cleaner for my soldering iron inbetween every joint. I was really excited when I plugged it in and saw the light go on, then....nothing.

The LED works, and the pedal has sound, it's just that with the volume and gain all the way up, it's about 10% as loud as my clean volume, with absolutely no gain to speak of.

And I did notice that the electrolytic cap in the BSIAB II that I got was rated for 16v. Not sure what that means, but I was careful to only run the pedal at 9v, and did not plug it into an 18v power supply for even a nanosecond. I thought I remembered reading something like that, and not to run at a power supply that's rated higher than an electrolytic cap in the circuit. I could be wrong but I wasn't gonna take any chances with that.

Ugh...

https://www.youtube.com/watch?v=KuVGcm7EfKU





I left out a .0022uF cap to give it more high end, and replaced another cap with a .001uF, the other .0022uF. I can't imagine how this could possibly cause these issues. But that's all I did that was unorthodox.

The parts that came with the pedal were a bit wonky looking, particularly the blue rectangle capacitors. I did some research online and to my knowledge these were the correct locations for those parts.

For the record, I did have 4 spare parts after I was done. The .0022 caps, which I expected, as I didn't use either...

And two other caps that I don't know the value of. I think they're .1uF, as I didn't see any traditional looking .1uF caps in the kit, and thought they were missing from the kit. I didn't realize that the blue rectangles other than the ones I had on the board were probably .1uF caps. I had some spare .1uF caps from when I was making the audio probe, so I used those. So I think all the parts that were left were ones I left out and replaced with my own of the same value, except that .001uF. Here they are, just in case:

[Slight Return]

Here are some measurements I just took of the BSIAB II I built today (not the Brownie). Power supply/9v terminal on PCB is reading out at 9.3v when hooked up to 9v power supply, with black probe on Ground.

Reversed the jacks...nope. They're in correctly.

There is a very midrangey sound to it..the gain is non-existent but from what little I can hear of the tone through the pedal, it sounds like it has a blanket over it. The tone is completely clean and very very quiet with the volume all the way up, and sounds like someone rolled the tone knob all the way off. Adjusting the tone knob on the pedal does not affect this, although it does change the static hum of the pedal as expected...I can hear the frequency going up so the tone sounds like it's working.

As for the transistors: All readings will be ordered Gate, Source, Drain:

Q1: 1.8v, 1.8v, 3.8v

Q2: 3.8v, 3.13v, 8.55v

Q3: 0.01v, 0.26v, 4.81v

Q4: 2.85v, 4.81v, 8.55v

Q5: 0v, 1.04v, 4.66v

Q5 Gate to Ground: 82.5k resistance

Q3 Gate to Ground: 535k resistance with Gain pot all the way up. Seems like normal readings throughout, with it tapering down in resistance as I lower the Gain knob until it gets to 0 at the bottom.

I still don't get how to read schematics, but it appears that Q2 Gate and Q1 Gate both go to ground through 1M resistors...my current multimeter doesn't have that setting. It goes between 200 and 2000k resistance and that's it. I tried testing resistance on Gate to Ground from Q1 and Q2 and got nothing, presumably because I can't set my meter to test them properly. Also assuming that I'm correct that they go through 1M resistors each to get to ground, which I could be wrong about.

These are all the measurements I have for now...but yeah. Almost zero volume, ZERO gain even with the gain knob all the way up.

[Slowpoke101]

Do not get discouraged. You have probably made a minor mistake when building the kit. Should not be too difficult to sort it out.

Check for a short between Q1's Gate and Source. They should not read the same.
If it is shorted once you clear it Q1 and Q2's voltages should make more sense.

Your multimeter can read 1M resistors quite easily. The 2000K range is 2M, so the meter's maximum resistance that it can read is 2M.

The 16V on the electrolytic means 16 volts - maximum. Go over 16 volts and it will get damaged.

The blue box type capacitors are 0.1 uF - The marking u1 means 0.1uF. The 63V means 63 volts maximum.

[duck_arse]

here, I'll type some random and confusing things about the circuit and stuff.

capacitor and resistor markings - to AVOID any possible errors with values, it was decided to replace the decimal point with the multiplier. so, instead of 2200 ohms, you'd put 2k2. with 0.1uF, you'd put 0u1, which is ugly, or use the multiplier that didn't need the decimal, ie 100nF. [many people don't like using the nano prefix, for some reason.]

0.000,001F = 0.1uF = 100nF = 100,000pF

you can also use the numeric code as on box-caps, 104 [which is 100,000 pF]. a 2k2 resistor would be 222. the "K" on your blue cap is the tolerance code. 63 is the voltage limit.

your circuit - Q1, Q3, and Q5 all have their gates referenced to ground, you just follow those resistors. Q1 should read a little over 1M. because they are ground referenced, the gates should read 0V DC. @ Slowpoke - check me here, please.

but, the gates of Q2 and Q4 are held mid-way between "supply volts" and ground because of the equal value resistors connected to them. your meter will read less than half V+, however, because it will load-down the lower resistor [making it look instead like a ~500k] when you measure.

and, to test. now you have sockets fitted, you can break the circuit into two parts, the front end and the arse end. IF you pull Q3 out of circuit, you can inject your test tones into the C1//R1//R2 junction, and then listen to the result at the C4//C5//R6 junction, and then thru the gain pot, and test at the empty gate-pin of Q3. if you get signal, and some gain, you can say front end is ok.

power off, refit Q3, and pull out Q1 and Q5 (for fun). now inject your test tone into the C4//C5//R6 junction, and monitor the result at the empty Q5 gate pin. work the drive pot, and you should have some gain control over a somewhat gained signal. if so, you have cleared most of the arse end, now power off, refit Q5, and then monitor your signal at the junction of C8//C9//R7. you should have signal, possibly less than before. now move through the tone section to the right, testing all the lugs of the tone pot, and the junctions following up to the output.

so now you've either found something, or cleared everything. record your voltages at each step [don't measure DC volts with a signal applied] and see what changes where. good luck, come back with some questions and or results.

[Slight Return]

I've gotta go to bed, but a couple parting thoughts before:

I audio probed the board. Perhaps it's significant that I was getting no audio from V1, which is the wire connecting the circuit board to the input of the Volume pot. I think it's the input, anyway. It's the rightmost tab on the Volume pot.

Q5 was, I think, the only transistor getting audio signal.

How should I test for a short in a transistor? What could cause a short?

What's the reason to not test voltage when the power is on? But it's okay to do that when adjusting the trimpot, right?

I hope I didn't damage anything by doing that. Probed around the electrolytic cap a few times as well. But I've been checking voltage on various parts with the power on. If that's not good then I'll stop doing it.

If I could eventually fix the Brownie AND the kit pedal, that would be great. That's what keeps me going. I know next to nothing right now so all this is to be expected. I'm gonna get some sleep.

I've been trying very hard to follow the schematic. I don't fully understand it yet but I can see how schematics go hand in hand with the audio probe. You have to know where you are in the circuit to identify where a fault is, and what that fault does to the components that follow it.

V1 getting no signal and that being the connection between the circuit board and the volume pot seems pretty significant, though I have no idea what it means. Thanks for the replies as always, will check up with all this ASAP.

[bluebunny]

What's the reason to not test voltage when the power is on?

Who said that?  As I hinted in my post on page #1, if you don't supply any volts (i.e. you don't power it up), then you can't expect to measure any volts anywhere in your circuit.  You don't get anything for nothing in this life, and that includes volts! 

If you're testing for voltages, it needs to be powered up.  If you're audio-probing, it needs to be powered up.  If you're testing resistance or continuity (same thing), then no power.

[Slowpoke101]

OK. A few things to clear up.

When doing resistance (or continuity) tests on a circuit the circuit must not be powered. If it is powered you would get some really weird measurements on your multimeter, none of which would make any sense.
When doing voltage measurements the circuit must be powered otherwise there would be no voltages available to actually measure. However you must be careful as not to slip with your multimeter's probes and cause a short circuit.
A short circuit can occur when something conductive (meter probe, sliver of solder (solder bridge), wire and so on) accidentally connects one part of a circuit to another part of the circuit. This accidental connection will stop the circuit from working in the manner that was intended.
Finding a short circuit can be difficult but quite often they are obvious (visual inspection). Using a multimeter set to continuity test (if it has it) or the low ohms resistance setting (200 on yours) is usually the best way to find a short if visual inspection is unsuccessful.

The V1 connection point actually is a ground point. There will be no audio on this connection (unless something is seriuosly wrong somewhere). The input audio connects to the I connection point. The output audio from the effect is the V3 connection point. This connection goes to the volume pot. If the effect is working there should be a very high level of audio at V3 (very loud).

Here are some voltages from my BSIAB2 (which is working). The voltage measurements where taken using a cheap multimeter and you will note that some are different from the GGG build document. This is normal and is due to my selection of transistors and using a cheap multimeter. With no input signal applied, battery at 8.97 volts and with Drive, Tone and Volume centred (mid-range) I get the following;

       Gate    Source    Drain
Q1: 0V       0.58V     5.08V
Q2: 2.98V   5.08V     8.94V
Q3: 0.01V   0.04V     4.56V
Q4: 2.98V   4.56V     8.94V
Q5: 0V       1.01V     2.64V

Now, as Duck pointed out the Gate's of Q1, Q3 and Q5 are tied to ground through some resistors. 0 volts or very close to 0 volts is expected at those Gates. The Gates of Q2 and Q4 are each connected to voltage dividers made up of two 1M resistors and you would expect to find the voltage on their Gates to be at half the supply voltage (4.5 volts) but the input resistance of the cheap multimeter loads down the voltage divider and gives us a false reading of a lower than expected voltage. This is nothing to be worried about but it is something to be aware of.
Notice that Q5 has a lower Drain voltage than what you currently have. This is again due to transistor selection and where I found the setting for the trimpot to sound "the best".

Your Q1 transistor is really odd with its voltage readings. As I said before, there is most likely a short circuit between its Gate and Source. If there is a short the effect cannot work. Let us know how you go.

***Edit: Ah, I see that bluebunny has covered the powered / not powered subject. Quite well in fact. Much clearer than my ramblings. 

[Slight Return]

@ Slowpoke

"Check for a short between Q1's Gate and Source. They should not read the same.
If it is shorted once you clear it Q1 and Q2's voltages should make more sense."

Do I check for a short by setting the resistance on the MM to 200ohms and then probing with the power off?

Either way, I just tried testing the resistance. If I didn't get a reading, I reset the MM to change how many digits there were until I did. Here's what I got:

BSIAB II Build:

Q1: Ground to Source: 38.2k, Source to Ground: 42.1k

Q2: Ground to Source: 42.7k, Source to Ground: 38.9k

Q3: Ground to Source: Starts at 230k, and kept increasing. I stopped after 10 seconds or so when it hit 260k. Source to Ground: Same thing.

Q4: 492k both ways.

Q5: 85k both ways.

CMATMODS Brownie:

Q1: 982k both ways.

Q2: 491k both ways.

Q3: 111k both ways.

Q4: 488k both ways.

Q5: 86k both ways.

Brownie Q1 to Ground: 982k

BSIAB II Q1 to Ground: 1k

It would appear that, somehow, on my BSIAB II build, Q1 is either not going to ground or bypassing the 1M resistor somehow? Or is it shorted out? I'm confused but I know that that isn't right.

I still want to get the Brownie running too. Not sure if those numbers help any with diagnosing what might be wrong. That pedal has a different issue, as it was working great for a while, and then just started spluttering and splatting and lost almost all volume and gain seemingly at random after playing for a while...whereas the BSIAB II simply does not work at all.

Sorry if I'm not providing all tests possible or responding to every post possible at the moment. I've read and re-read everything and am doing my best to keep up.

Next on my list will definitely be doing the audio probe test for the two ends of the pedal, as suggested by duck. 

[Slowpoke101]

You are getting some interesting results.
Is there any chance that you can post a picture of the solder side of the GGG BSIAB2 board please.

[Slight Return]

Here she is:

[Slowpoke101]

This post is concerning the GGG kit only.
Refer to the following picture;



Make sure that the pedal is in Bypass mode and is passing the guitar's audio to your amplifier correctly. If it does then move to the next step.
Disconnect power to the pedal, remove the input lead (from guitar) and the output lead (to amp), while leaving the pedal in Bypass mode.
Set your multimeter to resistance test 2000K range. Place the black test probe onto point 2 (refer to picture) and the red test lead onto point 1. You should read around 1M.
Now set your multimeter to the 200 range. Place the red probe onto point 5 (Q1 Drain) and the black probe onto point 3 (Q1 Gate). Your meter should display 1.
Move the black probe to point 4 (Q1 Source). Your meter should display 1 again.
If all this tests as described - no shorts are on Q1. Good.
Plug the guitar's input lead back in. Set the guitar's volume to maximum. Do not apply power to the pedal. No need to plug your amp in at this stage.

***Edit: Forgot this bit. Click the stomp switch once to set Engaged mode.

Set your multimeter back to the 2000K range and place the black test probe back onto point 2 (refer to picture) and the red test lead back onto point 1. Depending on your guitar's pick-up coils you should read above 2K (on the 2000K range 2K would be displayed as 002). If the measurement is lower than that check that the pedal's input socket is not shorting against the Drive pot's metal body.
Let us know what you find.

[duck_arse]

[clarify] sorry, when I said power off, I meant that if you are going to pull fets from sockets, or ram them into sockets, you should off the power, just in case. but then, once your parts are safely seated or removed, you power up, and go about your voltage measures. carry on. [/clarify]

[Slight Return]

@ Slowpoke

Point 2 to Point 1: I get nothing. Meter reads 000.

Point 5 (Q1 Drain) to Point 3 (Q1 Gate): Meter stays at 1.

Point 4 (Q1 Source) to Point 3 (Q1 Gate): 38.7k.

I didn't continue with the testing yet, as apparently this means there is a short on Q1. What could cause this, and what can I do about it?

[Slowpoke101]

***EDIT: Having just noticed that the stomp switch shorts the board's input to ground in bypass mode (sorry). Set the pedal to Engaged mode (with no power applied) and continue as described below.

When measuring points 1 and 2 your meter should be set to the 2000K range on the resistance test. If everything is OK you the meter should show 1000 or close to this. However you measured 000 which is a low resistance, possibly a short. Set your multimeter to the 200 range on the resistance test and remeasure points 1 and 2. If there is a short circuit the display would show something lower than 10.
Anyway, solder the input wire going to connection point I on the board. Remeasure points 1 and 2 with the meter set to the 2000K range. If everything is good the meter will show somewhere near 1000 which is 1M. If it does, good. If it still shows 000 then there is a low resistance or a short circuit somewhere with R1, C1 and R2. Look very closely and you should be able to find it. A fine sliver of solder can cause this and it can be hidden in the flux residue on the board.
Now, if the meter showed 1000 on the last test there may be a short with the input lead that was connected to the I board connection point. Look very closely at the terminals on the stomp switch as there may be a fine wire touch between terminals.

Don't worry about the 38.7K reading on Q1 yet. Sort out the problem with the input area first.

[Slight Return]

For points 1 and 2 in the pic:

With it engaged and the power off, and my meter on 2000K, I am getting 001.

If I put the meter on 200, then it reads 01.2.

Looked for about 15 minutes at the board on both sides at R1, C1, and R2, and re-fluxed, and re-flowed all those joints. I got a little glue brush with some isopropyl alcohol and cleaned all the flux off of the board, top and bottom, afterwards. While it was wet from the alcohol I could see pretty clearly, and I could not see anything bridging any of the solder joints. I carefully went in with a little toothpick and got a little blackened flux/solder out of the way in some spots but it didn't reveal anything.

Measured again, and....no difference. I couldn't see any pieces of solder bridging any connections. One of the caps they gave me was wonky (two legs very far apart, when the pads designated for it were very close together), but neither of the legs were contacting anything they shouldn't be.

I also looked over the stomp switch and could not see anything bridging anything between any of the terminals. Does the orientation of the switch matter at all? I just soldered it on following the wire diagram but I didn't know if it needed to be oriented a certain way or not. It just looked like a square with no indication of what way is "right side up," if there is one. Not sure if that matters.

[Slowpoke101]

Very interesting result.
De-solder the input wire (green) at board connection point I ( I - not test point 1). Set your meter to 2000K and measure again across test points 1 and 2. You should read around 1000. If it still reads 000 de-solder C1 (250pF capacitor - probably marked 251) and measure again. If it now reads 1000, C1 is probably faulty.
Set your meter to 200 and test across C1 whilst it is de-soldered from the board. If it shows near 000 it is faulty and should be replaced.
I am surprised that you are having trouble with the BSIAB2 kit as you have done a very good job building the circuit board.
Let us know what you find.