Help with under-performing Mudbunny

[Rich_S]

Aw, crud... my first pedal that didn't work right, first try.

It's a recent-rev Mudbunny built with Triangle component values.

Symptoms:  Actually, everything seems to work.  The pedal passes signal in bypass, and when activated.  The volume control turns the volume up and down, and the sustain control adds dirt.  The tone control sweeps like a Big Muff tone control should (based on my limited experience with a NYC Muff).  The problem is, the pedal isn't making anywhere near the amount of dirt it should.  It gets kind of crunchy/farty with the SUS all the way up, but doesn't approach the singing sustain and over-the-top dirt of a real BMP.  It makes some dirt on the low notes, but has very little effect on high notes (say, open E and B strings).
Note: All testing through Vox PF15, with the pedal powered from a 9-volt output of a Voodoo PP2+.

What I've done so far:

• As advised, took a few days off and ignored the pedal.
• Checked my wiring, both for correct routing and for bad solder joints.
• Checked all component values, reading them off the board with a magnifier and then comparing the as-built list to the B.O.M.  All components check out.  (BTW, I checked them all with a meter when I populated the board, to catch any off-spec values.)
• Checked polarity of diodes and transistors.  All are correct according to the silkscreen on the PC board.
• Visually inspected (with an illuminated magnifier) the soldering on the PC board for cold joints and bridges.  Found a couple that were suspect, but appeared to be okay once I scraped away some flux that was causing glare.

After all that, it's late, I have a headache, and I'm half-blind.  Tomorrow, I'll try to get some voltage measurements and post them.  In the meantime, anybody have any suggestions where to look?

[Haberdasher]

did you use 2n5088's?

it kind of sounds like the transistors are in there bakcwards, or you may possibly have a bad trannie in there.

[Rich_S]

Yes on the 2N5088s.  I have some spares, maybe try swapping them after I get the voltage measurements.

Also, in the spirit of "can't leave well enough alone" I spent some more time staring at the solder side with my little Rat Shack magnifier. I might have found a bridge across D3 and D4.  I scraped whatever was there away, but don't really think that was the problem.  Won't know until tomorrow if it made a difference.  I'm goin' to bed.

[Bret608]

I suspect transistor orientation too as I recently had the same problem with the Wolfshirt. I haven't built the Mudbunny--is the silkscreen on the board oriented for 2n5088s? I found it helps to look at the schematic as well and find what the emitter (the leg with the "arrow") connects to, then match that to the actual board layout. Lastly, google your particular brand and type of transistor to make sure the package/transistor pinout actually match the silkscreen. Sometimes, even when it seems like you can just follow the silkscreen image on the board, you'll find that for whatever reason your trannies need to be oriented differently.

Let us know how it works out!

[LaceSensor]

start just by flipping q4 (the buffer) 180 degrees and see if that works.
If so, it could be  a problem with the emitter resistor, I believe, based on experiences with the creamy dreamer BOMs

[Rich_S]

I'm confused.  If one or more transistors were in backwards, wouldn't it just not work at all?

Also, the Mudbunny project instructions call out the 2N5088 as the "normal" transistor, then goes on to say that we can use other transistors, but must be careful to get them oriented correctly.  I assume this means the board is silkscreened for 2N5088s, but don't know if this is a safe assumptoin or not.

Here's the pinout for the 2N5088 that I have, from a Fairchild data sheet.  No idea what manufcaturer made the trannies I have; I bought them from Smallbear.



I guess I'll check this pinout against the PC board layout and schematic tonight.  Four transistors is too many to just start swapping.


Edit, 102 minutes later:  Okay, I checked all four trannies, starting with the Fairchild pinout, and comparing the built-up board to the project layout to the schematic.  As near as I can tell, the layout & silkscreening are correct, and the transistors are all inserted right-way-'round.

[pryde]

Picture time.
Close detailed photos front and back please. Hopefully someone can spot the issue.

[Rich_S]

Before we get to the photos, here are the voltages on the transistors.  (Voodoo PP2+ power supply, Fluke 87 Multimeter)

+ Power terminal:  9.3

Q1
E: 0.172  
B: 0.730
C: 4.38

Q2
E: 0.099  
B: 0.692
C: 1.157

Q3
E: 0.000  
B: 0.003
C: 0.001

Q4
E: 1.199
B: 1.763
C: 3.813

Clearly the problem is in or around Q3.

Edit: I think I found it.  If I measure the high side of R17 on the resistor lead, I get zero.  If I measure on the pad, I get 9.14 volts.  If I push hard on the lead with the probe, it goes up to 9.14.  Cold solder joint on R17. Looking at it with the magnifier, it looks alright on the trace side, but on the component side, I can see a little dingberry of solder, floating in the middle of the hole.  I'll be back after a few minutes to warm up the ol' Weller...

[Rich_S]

Fixed!  I just reflowed the high side of R17 and added a bit more solder, and it's the nasty, nasty Muff it should be.

The Fuzz Sisters Live!

(Triangle Mudbunny  and vero Fuzzrite)

[pryde]

Awesome. Glad you got it going. Pics probably would not have helped with that issue.