Noob here. I made the Mangler 2014, and it seems to work fine - I measured every component before putting them in, and took embarrassingly long. I got a pair of Mullard OC76 from Small Bear and used his resistors as follows for the transistors
R1 = 110 K
R2 = 22 K
R3 = 11 K
R4 = 680 ohms
With the red lead on ground, and testing with the black probe, I get 2.5 volts at the test point.
On Q1, I get nothing at the emitter. Base is .114v, collector is .595v. When I touched the Q1 base with the probe, it made a sound through the amp, if that means anything.
On Q2, I get .496 on the emitter. Base is .586, collector is 2.47 and it kept going up
Pedal seems to work fine, fuzzes like crazy, bypass is fine. A for effort, and I still get ice cream after the game? Get em on the next Mangler?
Thanks,
Pat
I forgot, volume and fuzz pots are cranked, as is internal trim pot.
Too low of a voltage at the bias test point means too high resistance going into the collector of Q2. Are you also using the bias trimpot, or did you jumper that out and just use 11k for R3?
What I would do is go with the default set up. the 220R resistor and 20k bias trimmer means 11k is right in the center of the trimmer. You could easily adjust it from there to reach -4.5v.
Also, remember that -4.5v is a target but not necessarily definitive. Some fuzzes sound quite amazing biased lower. They take on a very squishy, Eric Johnson type tone.
I will remove the 11k, put in the 220R and dial in with the trim pot. Thank you very much. It is greatly appreciated.
Pat
I just thought of a good mod. An external switch that takes you from -4.5v down to about -3 to -3.5v. Call it "squish" ;)
Here, I typed up how I think the mod would work: http://www.madbeanpedals.com/forum/index.php?topic=15306.0
I did as you instructed, and the bias works perfectly. Thanks again.
The mod would be cool, because it did sound pretty badass in some applications with the 11k and 2.5 volts. Higher up on the neck it almost sounded like a very slight octavia and notes on the lower strings sounded enormous.