Green bean no effected signal

[mattc]

(1) Project Name:
Greenbean  2014

(2) General description of the problem:
When the effect is on all I get is hiss.   The tone control changes the tone of the hiss, and the level and drive are changing the hiss, but I get no guitar signal.

(3) Steps that you have taken to try to resolve the issue:
I tried cursing first, and that didn't help.  I checked all the solder joints and they look good.  I checked the orientation of the BC550s.  One was backward, so I flipped it, but no change.   I checked the continuity between the output pad and output jack and input pad and input jack, and those are fine, so I don't think it's the off board wiring.

(4) List any substitutions you used for parts/values:
I used BC550s in Q1 and Q2. 

Some readings from the meter:

Power in 9.09v
Ground -.1 mv
Pin 1 : 4.40v
Pin 2 : 4.42v
Pin 3 : 4.39v
Pin 4 : 0.2mv
Pin 5 : 8.79v
Pin 6 : 4.4v
Pin 7 : 4.4v
Pin 8 : 4.39 v

Q1 8.79v, 90mv, 3.54v
Q2 8.79v, 3.94v, 3.54v

Getting 4.4v on the (+) pads for the clipping diodes
Getting 8.85v on the (+) pad for D6

Any ideas?

[mgwhit]

Congratulations on making one of the best and most thorough Tech Help posts I have ever seen.  Future Tech Help posters should use this as a template.

The base of your Q1 transistor looks low.  I recommend measuring the voltage on either side of R3.  You may need to reflow the joints on R3 and Q1's base.  All other voltages look totally believable.  Good luck!

[jimilee]

I'd reflow everything.  The solder should flow through the hole like on your tone pot.


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[mattc]

I'll reflow everything, and report back.

[Govmnt_Lacky]

Might want to take a look at the pinouts for your transistors. Although the build doc references "Si" or Silicon... not all are the same.

For example. 2N3904 have a different pinout than BC550s 

EDIT: Disregard. Looks like you have them both reversed anyways..  Are you sure that R3 Dale resistor is a 470K?

[mattc]

I think it's a 470, but I'll double check that too.

One thing I didn't mention.... Should I get continuity between the in and R3?   I tried that and didn't get continuity.

[Govmnt_Lacky]

I think it's a 470, but I'll double check that too.

One thing I didn't mention.... Should I get continuity between the in and R3?   I tried that and didn't get continuity.

The R3 resistor is supposed to be 470K..... not just 470.

No. You should not get direct continuity between Input pad and either side of R3.

[mattc]

I've verified that all the values are correct.  I swapped the 550s for a pair from a different supplier.  I swapped the 4558 for a different one.  I swapped out the red LEDs for yellow.  I re-flowed all the joints.  No change 

One things that's interesting... my strobostomp is plugged in in front of the greenbean, when the GB is bypassed, the tuner works fine.  When I turn on the GB the tuner stops tuning, it still has power, but the strobe LEDs stop moving.  I don't have any clue what that means, but it's interesting?

Here are more pictures, maybe someone can see what's going on?

[mgwhit]

I've verified that all the values are correct.  I swapped the 550s for a pair from a different supplier.  I swapped the 4558 for a different one.  I swapped out the red LEDs for yellow.  I re-flowed all the joints.  No change 

Do you still have the low voltage on the base of Q1?  That's where the most obvious problem was.

One things that's interesting... my strobostomp is plugged in in front of the greenbean, when the GB is bypassed, the tuner works fine.  When I turn on the GB the tuner stops tuning, it still has power, but the strobe LEDs stop moving.  I don't have any clue what that means, but it's interesting?

That is a weird one, and it's probably a good clue once one of us figures out what it means.  But I'd concentrate on the simpler issue (i.e. the transistor voltage) first.  You know that no signal is getting through Q1 until that is corrected.  Also, the joints on your Fat switch look pretty bad.  Touch them up and add solder.

--

Added:  Hmmm.  I wonder if your C1 is bad and you're leaking DC onto your input.

Added later: I'm also disturbed by the fact that you don't seem to have 0V on ground.  That's worth looking into, too.

[mattc]

Q1 : 8.78, 3.92, 3.53
Q2 : 8.78, 3.92, 3.53

I get 0 for ground at the stomp breakout, but at the pcb it is 0.1mV.

The fat switch is about to get more solder....

[mgwhit]

Q1 : 8.78, 3.92, 3.53
Q2 : 8.78, 3.92, 3.53

Good.

I get 0 for ground at the stomp breakout, but at the pcb it is 0.1mV.

Hmmm.  Touch up that joint on the 3PDT breakout.  Maybe switch out that wire if that doesn't help.

[mattc]

Touched up the joint at the breakout, swapped out C1, and added solder to the fat switch.  No change 😞

[mattc]

So, some resolution here.   

I bought a new board, populated it, moved the transistors and chip from the non-working board over, and... it fired up right away.  I still have no idea what was wrong with the first one, but at least I have a working GreenBean now. 

Thanks everyone who offered help.

[madbean]

If you still have the old board and want to send it to me I will have a look at it. If the board itself is bad, I'll refund your second purchase. It's rare, but it can happen.

[mattc]

If you still have the old board and want to send it to me I will have a look at it. If the board itself is bad, I'll refund your second purchase. It's rare, but it can happen.

That's really cool of you.   I'll pull off the pots, and drop it in the mail to you.

Can you PM me your address (or point me to it on the web site).

Thanks!