Maestro Fuzz Tone No Output

[misterc57]

No signal injected. Noise is hiss and crackling (popcorn, rice krispies) is immediate at turn on. Temp is around 62F. I have more NTE158 I can swap out for a test.

I swapped Q2 with the NTE158. Noise is still there.

Also tried a new 22uF coupling cap at Q2 collector. Noise is still there.

[misterc57]

Have to put this one aside for now.

Can the collector resistors cause noise? I know plate resistors in the preamp tubes can make noise.

Thank you

[Helmholtz]

That's possible but transistor noise is much more likely.
Early Germaniums are known for aging problems.
Replace the resistors and see.

[mozz]

Don't be replacing random parts in a collectable pedal. And resoldering lowers the value. See what a untouched pedal goes for and you'll understand. That's why I said try to repair the broken transistor lead. It is possible as I have done it before, do not overheat it. To me NTE replacements are junk. If you want to find original 2n270s, you need to buy old RCA solid state radios and find what models used those. I have some but the package is black, the silver ones I do have I will not part with. If the owner really wants that sound, build a clone with transistor sockets and swap germanium with what you can until it sounds good. Sorry for being so harsh but if you followed diystompboxes you would understand more about rare/ collectable pedals.

[x-pro]

You need to remove the cap from the original transistor with the broken lead. Then solder carefully from the crystal side.

[Helmholtz]

To me NTE replacements are junk.

Why, what's the problem?

[mozz]

Well if that is all that is available, sure use them. They are just too generic of a replacement part. This goes back to the 70's, when you could walk in a store and buy your electronic parts, you can buy SK, RCA, ECG, HEP, GE, MOTOROLA, etc. Most of the time it would work. But rumor was these are sub standard parts, floor sweepings, parts that didn't make the grade. Transistor museum has interviews with original engineers who even stated the parts that didn't make the grade were sold off as "consumer/ hobby grade" parts.

Same with tubes, relabeled, rebranded.

Some of these old pedals, fuzz, boosters, overdrives, work best when you can source the original parts, not only transistors. You know for a fact germanium transistors were all over the board. NTE was known as ECG. Here are 3 ECG158 replacement transistors new in the boxes. 3 different transistor packages, most likely 3 different manufacturers. There can not be any level of consistency there. Also another picture of a true 2n270, different package. Also 3 pieces of 2n270 by Etco. These 3 transistors do not even work in my pedal clone.

I would put in anything i had around just to get it working, since Q1 is a emitter follower most any germanium would work. Most likely there are other problems than broken Q1 lead.

[Helmholtz]

I don't have own experience with NTE Germaniums.
But from an engineering perspective transistor leakage is not a desirable property.
So maybe NTE just makes better, i.e. less leaky transistors which won't work in position 1 and 3 of this circuit.
Reportedly Cesar Diaz made SRV a more reliable fuzz face board using NTE103s.

It should be possible to emulate transistor leakage by wiring a suitable high value resistor between collector and base.
Goal would be to achieve the same collector and/or emitter voltage as with a good sounding original.

[mozz]

Diaz old shop, run by Peter McMahon of Homestead amps is only a few miles from here. That was 5 years ago but i think Peter still is there. Schematics i seen had shown NTE 158 and or NTE103., I actually had these 4 pieces of 158 saved and was going to drop them off there.

[misterc57]

The owner asked to see if I could get it working. He plans to sell it.

My goal with these oldies is to preserve as much of the original components as possible. I appreciate the value in this approach.

Now I am trying to find the noise culprit and only replace what is necessary. I would restore all original components not contributing to issues.

I did not know I could remove the cap of the transistor to get to the internal leads. Is the cap difficult to remove, how is that done? I'm not good with tiny work.

Thank you

[Helmholtz]

My goal with these oldies is to preserve as much of the original components as possible. I appreciate the value in this approach.

I think we all have that in mind.

mozz what are optimum collector and emitter voltages?

[g1]

You need to remove the cap from the original transistor with the broken lead.

Can you explain how to do this?

[mozz]

Can you explain how to do this?

Was he just joking?

"mozz what are optimum collector and emitter voltages?"
Let me get back to you on that. I do have 2n270 but you have to swap them around to get any good sounds.
Q1E ~<1.0V
Q2C pot changes V value 0.5V-2.5V
Q3C~2.5V

Never really finished it to my liking. I may have had luck using 2n404,2n408 or some SFT352.

[Helmholtz]

Q1E ~<1.0V
Q2C pot changes V value 0.5V-2.5V
Q3C~2.5V

Thanks.
I asked because those voltages could help the OP to troubleshoot his unit.
From a technical perspective the unit should work when the emitter of Q1 and the collectors of Q2 and Q3 all sit at around half the battery voltage.
Regarding required leakage only Q1 and Q3 are critical.
Q2 has a an adjustable bias circuit, so even a non-leaky transistor should work here.

[misterc57]

Q1E ~<1.0V
Q2C pot changes V value 0.5V-2.5V
Q3C~2.5V

What I am seeing for V all negative...

Q1C 2.8
Q1B 2
Q1E 1.9

Q2C 2.5, varies 2.1 to 2.8
Q2B 60 mV, varies
Q2E 0

Q3C 2.5
Q3B 0, varies
Q3E 0