Maestro Fuzz Tone No Output

[misterc57]

Looking for suggestions on repairing an old Fuzz Tone.

Issues

No output
Broken leg on final 2N270. Replaced with a general purpose PNP for now.
On/Off is integrated in VOL pot and is open. Jumping for now.
Output cable is incomplete. I am using jumpers for now to connect to guitar amp.



Signal seems to flow from right to left on the attached schematic (which I hope to be the correct schematic).

I have audio signal at the collector of the first 2N270, no audio after that. I have -2.7 to -2.5 VDC at all collectors.

Pedal passes a clean signal. When I click to footswitch there is nothing.

Thank you!

[Helmholtz]

2N270 is a Germanium transistor. Cannot be replaced with a Si pnp.
Circuit depends on Ge transistor leakage. A Si transistor will lack base bias.
The first transistor is used as emitter follower and must not have signal at the collector.

[mozz]

Try to quickly solder a thin strand of wire on the broken transistor, may be able to fix it. Other than that, what Helmholtz said, you need a leaky pnp germanium transistor. Anything other than a real 2n270 will reduce the nice value of that pedal.

[Jazz P Bass]

There is a nice write up on the pedal here: https://www.coda-effects.com/2016/12...-fz1-1966.html

It also has circuit description towards the end of the article.

[misterc57]

No luck trying to attach a wire to the old 2N270. What about using a NTE158?

[mozz]

158 is good, often used in fuzz faces. You can find old germaniums in AM radios, old walkie talkies. If you want a transistor that will work i can mail you one.

[misterc57]

158 is good, often used in fuzz faces. You can find old germaniums in AM radios, old walkie talkies. If you want a transistor that will work i can mail you one.

Thanks for the offer. Let's see how things play out.

I installed the 158. All I get is white noise when clicking the switch.

[DrGonz78]

I bought a big bag of old germanium’s years ago while reworking a vox jaguar keyboard. Ordered from a guy in Sophia, Bulgaria. What makes that pedal sound the way it does is by having germanium’s on hand because you might need to try out a few to match it to the circuit. When I play around with these fuzz circuits I now always install a nice biasing trimmer. This just got me thinking to try to create a circuit that can adjust between germanium and silicone in the same circuit. That would be cool!

[Jazz P Bass]

"Signal seems to flow from right to left".

The signal flows from left to the right.
The volume pot is the output.

[misterc57]

"Signal seems to flow from right to left".

The signal flows from left to the right.
The volume pot is the output.

Yes I mixed that up. Now that I have plugged the guitar to the input I have signal and fuzz.

However there is a lot of unwanted noise. Hissing and crackling with or without a guitar plugged in.

[misterc57]

Noise seems to be coming from the 2nd PNP. No noise before at the E or B, noise at the Collector.

[mozz]

Freeze spray q2, noise should go away. Make sure those electrolytics are good.

[misterc57]

Freeze spray q2, noise should go away. Make sure those electrolytics are good.

Caps seem good. Yes noise went away with freeze spray on q2. Does that mean bad q2? Thank you

[mozz]

Well, not necessarily. It's been hot here and some germanium start to leak a lot on rising temps. All i can say is 65-70f should be bearable. Anything hotter and it gets real noisy, such as a stage, it may be too much noise to use. Does it sound like popcorn or hiss? Sometimes a 47pf or 100pf across the C-B will quiet the noise, yet also kill some high freqs, maybe too much.

[g1]

The other question is whether you are running signal along with the noise. If you are, and both the signal and noise cut out, it just means you have turned off the transistor. With the transistor off, nothing from Q2 or ahead of it will be heard at the output.