Superfuzz Build - Poor Transistor Values

[R.G.]

Sounds like it may be time for back to basics.

Give us a full wrap up of the data requested in "What to do when it doesn't work" and we'll dig in. That will cut a lot of time off this.

[Arcane Analog]

What layout/PCB are you using? Is it verified?

[PRR]

Pull the transistors, pull the base caps, find out why the base bias voltages are way-high.

My guess is a wrong resistor value. You may have to lift one leg of each resistor to check this.

[killerkev]

Sounds like it may be time for back to basics.

Give us a full wrap up of the data requested in "What to do when it doesn't work" and we'll dig in. That will cut a lot of time off this.

I agree, getting frustrated so I'll refer to that post and answer each item

[killerkev]

Sounds like it may be time for back to basics.

Give us a full wrap up of the data requested in "What to do when it doesn't work" and we'll dig in. That will cut a lot of time off this.

1.Name of the project: Univox Superfuzz, from www.pedalparts.co.uk.

2.Links to the source of the project web site with the schematic or project, layout and wiring diagram. http://pedalparts.co.uk/wp-content/uploads/2013/02/SuperFuzz.pdf

3.Some candid admissions about how closely you followed the suggested layout, if any. Followed the part diagram completely except for the power filter electro cap of 100 uf and used a 220 uf instead

4.Any parts substitutions or modifications you made to the original: The 1.8K resistor (R19). I did not have this value so I placed a 1.5K  & 270 ohm resistor in series to substitute. Again, did the same at the other 1.8K resistor (R4). Transistors used are 2N222 manufactured by Central Semi Corp. Datasheet here: http://www.mouser.com/ds/2/68/2N2221-28620.pdf
"Did you check the pinout of that transistor?" "Yes, I did a google search on that part number and check the pinout against how I soldered it in."

5.Whether or not it's a positive ground circuit : It is negative ground circuit.

6.What it does and does not do how it works; I plugged it into an amp and played through it. There is a huge volume drop when engaged and I can hear the effect but it is seriously gated. Sounds like it could be awesome if I can get rid of the gating and volume drop!

7.Turn your meter on, set it to the 10V or 20V scale. Remove the battery from the battery clip. Probe the battery terminals with the meter leads before putting it in the clip. What is the out of circuit battery voltage? => 9.35V

Voltage at the circuit board end of the red battery lead = 9.28V
Voltage at the circuit board end of the black battery lead = 0.0V


Battery – 9.35 V

Q1 C-5.10   Q2 C-9.28   Q3 C-5.87   
      B-0.70         B-5.10       B-3.91         
      E-0.14         E-4.51         E-3.34   

Q4 C-1.53   Q5 C-1.53   Q6 C-3.59
      B-2.00         B-2.03         B-1.16
      E-1.45         E-1.45         E-0.56

D1
A (anode, the non-band end) = 0.0V
K (cathode, the banded end) =0.0V

D2
A =0.0V
K =0.0V

No voltage on any side of the diodes?

[killerkev]

can i just check what's going on with your trimpot / lack of trimpot? do you have the two outer pads connected to the centre pad with jumpers? if you're removed the trimpot you need to do this to ground the 22k resistors from bases of Q4 & 5.
sorry if that sounds obvious, but it isn't clear what you have jumpered.

i don't think i've ever measured voltages on something before plugging it in and trying it. i trust my ears over numbers any day of the week.

Good News! I did what you said about placing the two jumpers to ground which they weren't before and transistor values came back to life!

Q4 C-3.33   Q5 C-3.33   
     B-1.67         B-1.67
     E-1.08         E-1.08   
I guess I originally had my trimpot in incorrectly and this is where the mess started. Gotta plug it in!   

[DiscoVlad]

Edit: Removed irrelevant troubleshooting comment.

Looks like you've got it working, well done!

Just out of interest, how large is the board from that kit? Does it fit into a 1590B?

[killerkev]

Yes, it fit's with plenty of room. That's the enclosure size I used. The PCB is small, the measurements are on the website. Had to breakout the magnifing glass for this board. The pedal sounds killer, has many different voices when used with my clean or dirty channel on my amp. I added a switch to go to either Ge or Si diodes. Again many different useful voices

[pedal parts]

glad you got it working bud.

just to clarify - the voltages would have read lower with the trimpot in place - see my measurements earlier in the thread. it still sounds great.