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Re: Maestro Fuzz FZ 1B Help

12/19/2003 4:14 PM
Doug B.	Re: Maestro Fuzz FZ 1B Help Is this the schematic? ftp://ftp.ee.ualberta.ca/pub/electronics/cookbook/audio/guitar/maefuzz.gif - Doug B.

12/20/2003 3:23 PM
Daver	That's very close. The differences are around the "Squelcher" circuit. The diode doesn't have any resistor in series with it. A 3.3M resistor goes from the base to ground. There is also a 680K resistor that goes from the base to the junction of the diode and the .1uf cap. There is no 100K resistor in parallel with the afore mentioned .1uf cap. The transistors are the small black TO-92 case style. I don't know if they're germanium or not. I'm going to try replacing all the transistors with hopefully something close. If that doesn't fix it then this is just the way it sounds. I don't have anything to compare it to. I hear some of the same "cutoff" problem on the Meastro sound samples ont the ToneFrenzy website. Thanks. Daver

12/20/2003 3:23 PM

Daver

That's very close. The differences are around the "Squelcher" circuit. The diode doesn't have any resistor in series with it. A 3.3M resistor goes from the base to ground. There is also a 680K resistor that goes from the base to the junction of the diode and the .1uf cap. There is no 100K resistor in parallel with the afore mentioned .1uf cap. The transistors are the small black TO-92 case style. I don't know if they're germanium or not. I'm going to try replacing all the transistors with hopefully something close. If that doesn't fix it then this is just the way it sounds. I don't have anything to compare it to. I hear some of the same "cutoff" problem on the Meastro sound samples ont the ToneFrenzy website. Thanks.
Daver

12/21/2003 12:52 PM
Doug B.	Daver - Interesting. The rest of the circuit is pretty much the same then? There often seem to be many "variations" of the old-timey/classic circuits... and i've found circuits that even had differences from the factory schematic that came with the effect! So i'm always appreciative when someone documents variations -- thanks! As far as i know, no germanium devices ever came in the TO-92 package. What are the actual markings on the transistors? - Doug B.

12/21/2003 12:52 PM

Doug B.

Daver -

Interesting. The rest of the circuit is pretty much the same then? There often seem to be many "variations" of the old-timey/classic circuits... and i've found circuits that even had differences from the factory schematic that came with the effect! So i'm always appreciative when someone documents variations -- thanks!

As far as i know, no germanium devices ever came in the TO-92 package. What are the actual markings on the transistors?

- Doug B.

12/21/2003 1:09 PM
Daver	Doug, The rest of the schematic is exactly the same as the one you linked. This one seems to match the factory schematic on the effect. The transistors are labeled "MH" with "9631" under that all in white ink. I'd like to know what they are. I want to try replacing them. If that doesn't change anything, then it sounds the way it sounds and it will be forever dubbed the A$$ Tone. Daver

12/23/2003 9:55 PM
Doug B.	I just breadboarded it! (long) I just searched through 8 old semiconductor data and cross-reference books and 3 newer software cross-reference programs and found... zilch for MH9631. (I did find MH9630, but that could be miles and miles away.) It must be one of those "house numbers from hell". Anyway, someone recently asked about (i believe) this same fuzz over at the other DIY effects forum, and one of the contributors (Dan N) said that the part number given in the web schematic (991-002298 not MH9631) corresponds to 2N3391A. This part was popular in its day and is still widely available. (Watch out though -- the pinouts on mine are ECB!) So i just breadboarded the circuit with 2N3391As and the squelcher circuit as described above by Daver. I left out the "mixer" part at the end -- i just wanted to see how the core circuit sounded. It's just a follower stage up front (Q1) then two stages of gain (Q2 and Q3). The third stage has a "squelcher" circuit on the emitter (Q4). I auditioned the output from stage 2 and the output from stage 3. Stage 2 sounded more or less like a crunchy overdrive, as one might expect. Stage 3 was more interesting: a nasaly (asymmetrical) fuzz, remiscent of a '60s-type fuzz, but too misbiased -- the notes would kinda fade in and out. (It acted the same way with the squelcher circuit removed.) So i changed out both collector resistors for ones 10 times smaller -- from 100k to 10k for stage 2 and from 470k to 47k for stage 3. (These are more-typical values for a self-biased common-emitter stage.) Much better! Still nasaly/asymmetrical, but consistent throughout the duration of note, and much stronger fuzz. Definitelty playable now. The squelcher was effective... and FUN! It didn't seem to mess with the attack portion of the note and only kicked in on long decays. Anyway, here are the voltages i measured on my breadboarded circuit (regulated 9.00 volts supply, no signal): Stage 1 - Q1: collector = 9.00v base = 6.46v emitter = 6.04v Stage 2 - Q2 (with 10k Rc): collector = 1.59v base = 0.61v emitter = 0.00v Stage 3 - Q3 (with 47k Rc): collector = 1.27v base = 1.07v emitter = 0.52v (= Q4 collector) Squelcher - Q4 (from Daver's description): collector = 0.52v (= Q3 emitter) base = 0.58v emitter = 0.00v junction of diode and 680k = 1.02v The collector and base voltages for stages 2 and 3 seem kinda low... but were even lower with the original collector-resistor values! I don't know how much the resistor changes will help if you're working on an original unit. I'm wondering if the web-schematic collector-resistor values are typos -- there have been a number of mistakes reported in that group of schematics... and even mistakes on schematics from manufacturers! So you might want to double check the actual resistor values on the board against the schematic. Just for info, here are a couple of user reviews of original FZ-1B units describing the sound: http://www.harmony-central.com/Effects/Data/Maestro/FZ_1B_Fuzz_Tone-01.html Anyway, let us know how it all works out.... - Doug B.

12/23/2003 9:55 PM

Doug B.

I just breadboarded it! (long)

I just searched through 8 old semiconductor data and cross-reference books and 3 newer software cross-reference programs and found... zilch for MH9631. (I *did* find MH9630, but that could be miles and miles away.) It must be one of those "house numbers from hell".

Anyway, someone recently asked about (i believe) this same fuzz over at the other DIY effects forum, and one of the contributors (Dan N) said that the part number given in the web schematic (991-002298 *not* MH9631) corresponds to 2N3391A. This part was popular in its day and is still widely available. (Watch out though -- the pinouts on mine are ECB!)

So i just breadboarded the circuit with 2N3391As and the squelcher circuit as described above by Daver. I left out the "mixer" part at the end -- i just wanted to see how the core circuit sounded. It's just a follower stage up front (Q1) then two stages of gain (Q2 and Q3). The third stage has a "squelcher" circuit on the emitter (Q4). I auditioned the output from stage 2 and the output from stage 3.

Stage 2 sounded more or less like a crunchy overdrive, as one might expect. Stage 3 was more interesting: a nasaly (asymmetrical) fuzz, remiscent of a '60s-type fuzz, but too misbiased -- the notes would kinda fade in and out. (It acted the same way with the squelcher circuit removed.)

So i changed out both collector resistors for ones 10 times smaller -- from 100k to 10k for stage 2 and from 470k to 47k for stage 3. (These are more-typical values for a self-biased common-emitter stage.) Much better! Still nasaly/asymmetrical, but consistent throughout the duration of note, and *much* stronger fuzz. Definitelty playable now.

The squelcher was effective... and FUN! It didn't seem to mess with the attack portion of the note and only kicked in on long decays.

Anyway, here are the voltages i measured on my breadboarded circuit (regulated 9.00 volts supply, no signal):

Stage 1 - Q1:

collector = 9.00v
base = 6.46v
emitter = 6.04v

Stage 2 - Q2 (with 10k Rc):

collector = 1.59v
base = 0.61v
emitter = 0.00v

Stage 3 - Q3 (with 47k Rc):

collector = 1.27v
base = 1.07v
emitter = 0.52v (= Q4 collector)

Squelcher - Q4 (from Daver's description):

collector = 0.52v (= Q3 emitter)
base = 0.58v
emitter = 0.00v
junction of diode and 680k = 1.02v

The collector and base voltages for stages 2 and 3 seem kinda low... but were even *lower* with the original collector-resistor values! I don't know how much the resistor changes will help if you're working on an original unit. I'm wondering if the web-schematic collector-resistor values are typos -- there have been a number of mistakes reported in that group of schematics... and even mistakes on schematics from manufacturers! So you might want to double check the actual resistor values on the board against the schematic.

Just for info, here are a couple of user reviews of original FZ-1B units describing the sound:

http://www.harmony-central.com/Effects/Data/Maestro/FZ_1B_Fuzz_Tone-01.html

Anyway, let us know how it all works out....

- Doug B.

12/24/2003 11:44 AM
Daver	Doug, Well thanks! That's great work you did. The notes do kind of fade in and out on this one too. Did the notes cut off as the sustain of the string faded? This one sounds very nasaly and harsh as well. Maybe it's working as intended. The schematic on the pedal has those higher value collector resistors and the circuit does indeed match that. Maybe the schematic is wrong and the assembly dept. just followed what they saw. I'll find out from the owner if he wants me to "mod" the pedal with those lower collector R values. I have some NTE 123AP transistors coming to try out, too. Don't know how they'll work. I appreciate all the help Doug! That's just great. I'll let you know how it works out. Merry Christmas, Happy Holidays! Daver

12/24/2003 11:44 AM

Daver

Doug,
Well thanks! That's great work you did. The notes do kind of fade in and out on this one too. Did the notes cut off as the sustain of the string faded? This one sounds very nasaly and harsh as well. Maybe it's working as intended. The schematic on the pedal has those higher value collector resistors and the circuit does indeed match that. Maybe the schematic is wrong and the assembly dept. just followed what they saw. I'll find out from the owner if he wants me to "mod" the pedal with those lower collector R values. I have some NTE 123AP transistors coming to try out, too. Don't know how they'll work. I appreciate all the help Doug! That's just great. I'll let you know how it works out. Merry Christmas, Happy Holidays!
Daver

12/26/2003 6:27 PM
Daver	Update OK, I put in the new NTE 123AP transistors and changed the collector resistor values to the ones Doug suggested. It sounds much better. But, there still is that threshold thing where you have to hit the string just hard enough for it to trigger and it cuts off as the signal decays. This gets worse the more the balance control is turned towards more fuzz and isn't there when you're getting mostly the "clean" portion of the signal. My voltages are similar in value and proportion to the ones Doug posted. My Q1 is different, though. C=8.89v (using a 9v battery), B=8.15v and E=7.74v. Any one see a problem here? I've replaced the transistors and verified the values of all resistors, pots and caps. Does this thing just suck that bad? Am I expecting too much? Daver

12/26/2003 6:27 PM

Daver

Update

OK, I put in the new NTE 123AP transistors and changed the collector resistor values to the ones Doug suggested. It sounds much better. But, there still is that threshold thing where you have to hit the string just hard enough for it to trigger and it cuts off as the signal decays. This gets worse the more the balance control is turned towards more fuzz and isn't there when you're getting mostly the "clean" portion of the signal. My voltages are similar in value and proportion to the ones Doug posted. My Q1 is different, though. C=8.89v (using a 9v battery), B=8.15v and E=7.74v. Any one see a problem here? I've replaced the transistors and verified the values of all resistors, pots and caps. Does this thing just suck that bad?

Am I expecting too much?
Daver

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