mudbunny problem

[britpeace]

 I just finished building a single sided mudbunny, to creamy dreamer-esq specs w/ the exception of using 470pf values for all the gain stages, instead of the 560pf values, and 47n caps instead of the 50n's.

My problem is it when I have it on, it sounds farty and weak, and generally just wrong... I went through w/ an audio probe and it seems everything sounds right up until q4 transistor, where it just sounds flabby and weak at all three legs of the transistor, like it's misbiased or something. Also, all the transistors voltages measured normal except for the q4 one, which measured really low (I think it was like .25 on the collector)... Ive tried replacing resistors, capacitors, and of coarse replacing the transistors in that area, but it's still not working properly. Ive also went through and checked all the values, pinouts (2n5088's have flipped pinouts compared to the bc549c on the single side layout), and wiring to make sure they were all correct, which they were.

I was wondering if anyone has had this problem before, or any suggestions/help. Thanks

[mgwhit]

It certainly doesn't have anything to do with your parts substitutions.  If your Q4 isn't biased correctly and you get a decent signal up to Q4 that's definitely where your problem is.  With a single-sided board it's very easy to have a solder bridge, or you could even have a broken trace.

Quadruple check the values of R20, R21, R22 and R23.  R23 stands out as the potentially tricky one as it is 390R and not 390K.

Clear photos of both sides of the board would help.  Good luck!

[britpeace]

Here's one side.

[mgwhit]

Okay -- it looks like you have two resistors "teepeed" in series for R23, and I can't see the color codes on those two.  What's going on there?

[britpeace]

It's just a 270r and a 120r.

[britpeace]

Using the audio probe, it doesn't start sounding weak or messed up until after the 3rd transistor stage. That's when it gets all crackly and weird. I've replaced it, I've checked all the values of every part, I've done everything I can think of. Still the same thing. I'm at a loss. 

[jkokura]

Brit, I think if you're experiencing problems but getting sound that usually is an indication that there's a problem on the PCB. For sure you've checked all the parts, and I'm not doubting you, but the problem will be on there and we all understand how hard it is to find sometimes. Be encouraged! I have only had 1 PCB defeat me out of the multitude I've worked on that needed trouble shooting.

My first thought is that you've got a cold solder joint or a bridge. It's easy to get the common voltages for Muffs, so if you are getting discrepencies than that should give you an indication of where to look. If you're getting bad sound after q3 than the problem might be at or around q3 OR q4, so check the voltages there, then look at the parts. I recommend sitting down with a copy of the schematic and a pencil and making notes about both the sound and any voltages. Don't assume your soldering is good, or that your parts are correct - sometimes they can look fine and aren't, and sometimes they can be marked incorrectly!

keep up the same steps, and take a break if you need it.

Jacob

[britpeace]

Has anyone actually built the Creamy Dreamer/Mudbunny on the single-sided version?

[britpeace]

Finally got this thing working... It was the recovery stages transistor biasing resistors. The Creamy dreamer spec layout did not work w/ the 2n5088 transistors, so I changed that section to the "mayo" values (r21, r22, r20, and r23). Once I did this it immediately sounded great and needed no other fixing, or tweaking. I actually don't think it was my fault on this one because my solder joints, component values, and wiring were perfect. It just wasn't working w/ the creamy dreamer values on the recovery stage. I don't know if it was the transistors I was using, or if theres an error w/ the values on the layout, but if anyone else ever has this problem w/ the q4 transistor, try reverting to one of the other big muff specs for this section, and it will work. Sounds really nice now! I'll post pics ASAP. Thanks for all the help guys!

[bigmufffuzzwizz]

Good you got it working. I haven't tried building a full Creamy Dreamer version yet, and not on a single sided board. Seems strange to me, I'll have to try bread boarding it when I get a chance. I'm very curious if I get similar results.

[dwstanford]

Ive breadboarded the creamy dreamer version following IvIark's vero layout and i was able to get it working, but i seem to remember having to make some alterations.  It's been a while, so i cant remember specifically but i do remember it didnt work correctly the first time.

[yanko_mr]

I need help, i try the dreamy creamy version but i have no sound at all...