Fuzz Face Clone Problems

[Unluckyfett]

I built a FF clone following BYOC's Schem using BC108's. It works and sounds great with a Tele, and a Hagstrom Super Swede, but as soon as I plug either of my Strats in all i get is uncontrolable, roaring,  growling, screeching, feedback unless i slam signal through it. I thought it might be i was too close to the amp so i went to a different room to the same problem. Ive tried biasing it all over the place. its either underbiased or feedback. The value of the high cut cap (idk if thats what its called) is correct but its ceramic instead of silver mica like BYOC ships. Could that be the problem? Also any other ideas? Thanks

Board Pre wiring in enclosure



Final (mediocre) product (its sloppy)

[Kesh]

Which letter comes after the BC108? If C or even B, they are probably too high gain and maybe this is causing the oscillation.

One trick is to place a 100pF cap across from base to collector on one or both transistors.

Another thing to try is replacing the 1M resistor from input to ground with 560K or thereabouts.

[brett]

Hi
+1 for too much gain.
Try the well-liked 2N2369 or other transistors with hFE around 100. 150 max.
Power bjts like the BD139 are perfect. Maybe it's my imagination, but they might sound better (higher B-C capacitance maybe?)
cheers

[LucifersTrip]

Even though I also prefer using lower hfe transistors, you still should have no problem with oscillation if the circuit is biased/set up correctly.

The higher hfe ones will just give you a mushier, sometimes synth-like, cheesier modern tone.

Small caps across BC will kill high end sizzle/harshness, but I haven't had much luck with them killing oscillation...unless you make them too large.

What are your voltages...and link to the schematic

[Unluckyfett]

UPDATE: sorry for the delay i thought i was subscribed to my own post but i was wrong. I changed the ceramic high cut cap (again idk if thats what its called) to a small tantalum cap and tried it on a different amp and i had no problems at all. long story short i tried on a few amps and no problems until the amp i originaly had the problem with.

It doesnt like my Marshall MA100H going through a 1960A.

It works fine on:
Fender Hot Rod Deluxe
DIY Fender Champ clone
Metroamp 69'spec Marshall Superbass
Metroamp Marshall JTM45
Battery powered "G-Blaster"

I play the MA100 on Clean Channel on 8 with bass 6 mid 5 treble 4 presences, resonances reverb all that stuff on 0.

Again only with strats it sequels and has problems so could it just be an input gain issue so i could put the 1m from in to ground on a switch with a smaller value like Kesh suggested but have it be more versatile

I think my next order of parts i might buy some of the transistors brett suggested to try. that BD139 looks very interesting

I don't have the pedal with me to get voltages right now but heres a link to the schem http://buildyourownclone.com/esvfuzzinstructions.pdf#page=16
the only change is I added .001 like suggested in the pdf when running bc108's to cut high freqs

thanks for the info everyone