Silicon FF (BC108c) on bredboard sounds great but oscilates like hell

[mac]

If it is on the breadboard, start over, it will take you only a couple of minutes to re-wire it.
Anyway I'd use lower gain Si, like BD139-10, MPSA42 or 2N2369A.
BTW, I had oscillation once while breadboarding a FF, because I was taking the output from Q2 collector.

Cufk JD factory! The sound like crap! I say my FF are the best in all Argentina

Apuesto 1.000 mangos a que no! 

mac

[slideman82]

If it is on the breadboard, start over, it will take you only a couple of minutes to re-wire it.
Anyway I'd use lower gain Si, like BD139-10, MPSA42 or 2N2369A.
BTW, I had oscillation once while breadboarding a FF, because I was taking the output from Q2 collector.

Cufk JD factory! The sound like crap! I say my FF are the best in all Argentina

Apuesto 1.000 mangos a que no! 

mac

Si te los apuesto los gano! Si los tuviera... pero no creo que sea para tanto! Los 128 suenan muuuuy bien, pero mejor los Mullard OC84. Lo malo de los Matsu es que tienen menos definicion, pero siguen siendo los de mejor calidad. Habra que usarlos en algun otro pedal.

[mac]

Proba los 2n1114 o 2n388 Texas Inst.

mac

[slideman82]

Well, this is a tunned FF I made for the guy in the video, he's playing through a horrible MG15 and, I think, a digital Boss multi-effect pedalboard (I'm not sure about this). The FF I think has a AC151 and a AC128. Enjoy, he plays a nice solo!

http://www.youtube.com/watch?v=q6zqOS1DvI8

Mac, I've tried 2N388, they're excellent!

[yeeshkul]

guys can a circuit-board like this (with ground all around) prevent oscillation as well?



Jan

[wilkins]

hi Jan.

I just done my FF mod, my status this same as you, I use a pair of BC108C (Q1 523 hFE, Q2 648 hFE - Check by DMM), cap value 2u2(input), 22uF(with 1K Fuzz pot), 0.01uF (output), common FF schematic , Biasing  Q1 - C.1.27   B.0.59  E.0.00, Q2 - C.4.81  B.1.27  E.0.65, and the sound has no oscillation .

Then I replace all carbon film resistor to carbon composition resistors, use same cap and similar bias voltage, this has oscillation, mush better than carbon film resistor on my ear .


I don't know why, but I made my FF be my perfect 

[amz-fx]

Grounding is critical in the FF.

Let's pick a ground point...  the ground lug of the output jack, for example.

The 1k drive pot should connect to the ground lug on the jack.  The ground wire from the breadboard also goes to the jack's ground lug (not to the drive pot). This should be an improvement.

You could parallel the 100uF that RG suggested with a 0.1uF ceramic disc.

Last resort...  disconnect the grounded emitter of Q1 from the breadboard ground point. Solder a wire to Q1's emitter and run that wire to the ground lug on the output jack.

Keep input and output wires separated by at least an inch (2.5 cm). Also make sure there is no flux residue on the board from your soldering.

regards, Jack

[ambulancevoice]

Last resort...  disconnect the grounded emitter of Q1 from the breadboard ground point. Solder a wire to Q1's emitter and run that wire to the ground lug on the output jack.

or better, yet, since this is a bread board, use an alligator clip w/ wire attached to the emitter and connect it to ground
spares him the trouble of the possible chance of frying his transistor

[amz-fx]

or better, yet, since this is a bread board, use an alligator clip w/ wire attached to the emitter and connect it to ground
spares him the trouble of the possible chance of frying his transistor

I'm not sure what you are saying, but the point I'm making is to take the emitter of Q1 directly to the star ground point that has been established on the jack lug and isolate it from the board ground. 

regards, Jack

[ambulancevoice]

i know what you meant

[sshrugg]

guys can a circuit-board like this (with ground all around) prevent oscillation as well?

Hey, yeah!  Good question.  I've got no idea!