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Maestro Fuzz FZ 1B Help


 
12/13/2003 6:12 PM
Daver
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Maestro Fuzz FZ 1B Help
I'm working on this fuzz pedal a friend got for nothing. It didn't work, now it sort of works. The fuzz is very weak and turning the balance control to one extreme loses the signal. The volume and on/off switch work fine. I'm a tube guy lost in transistor land. ;) Any ideas where to start to look? Also what is supposed to hold the board in this thing? It's not held down by anything and could short out on the stomp switch and jacks. Thanks for any info you can provide.  
Daver
 
12/13/2003 6:24 PM
Rick Erickson
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A good place to start with a pedal this old is to replace any and all electrolytic caps in it. Then check the value of all carbon comp. resistors. They tend to drift with age, sometimes drastically.  
If you have a meter with a diode test function you can check the transistors out of circuit for shorts or open circuits. C-E should read open in both directions, B-E and B-C should read like a diode junction. The schemaic is all over the internet so you shouldn't have any problem finding that.  
Finding a diagram (a free one anyway) for the Maestro OB-2 Octave pedal seems to ba a bit more of a challenge.  
 
RE
 
12/13/2003 6:37 PM
Daver
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Rick,  
Thanks. There aren't any electrolytics in this thing. All the resistors check out very close to spec. There is a schematic pasted on the bottom plate, so I've lucked out there. ;) I guess I'll have to pull the transistors out and test them. I was hoping to do the least invasive repair I could, but that's life. I'll check them out. Thanks!  
Daver
 
12/14/2003 10:14 AM
Daver
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Update
Well after touching up some solder joints it works a little better, but sounds terrible. It only fuzzes loudly if you hit the strings harder and is very quiet if you back off. I checked the transitors in circuit according to the Geofex site and found one where the base and collector are at the same voltage ~ 5.54v. I pulled this one and it shows nothing (0) on my meter. Measuring as Rick suggested as a diode test, it reads normal. I've never used the transistor test function on my meter, so I'm not sure what to expect, but I thought "0" was wrong. This particular transistor has its' collector directly connected to another transistors emmitter and is called a "Squelcher" on the schematic. Could the other transistor be the one that's throwing things off? Any help apprecisted.  
Daver
 
12/15/2003 7:48 PM
Rick Erickson
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quote:
"I pulled this one and it shows nothing (0) on my meter. Measuring as Rick suggested as a diode test, it reads normal. I've never used the transistor test function on my meter, so I'm not sure what to expect, but I thought "0" was wrong."
 
 
Not quite sure what you mean here by "reading 0". Is it reading 0 ohms across that particular junction? Do you mean there is zero voltage drop across the b-c junction? This could be caused by a bad connecrion or component. I don't have the FZ-1B schematic. Any chance you could scan it and email me?  
O.K. - I get it, your transistor test function reads zero. What parameter is it measuring? Beta?  
I would measure some known good transistors to get e feel for the meter. You might just have the leads connected incorrectly.  
 
RE
 
12/15/2003 10:49 PM
Rick Erickson
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Re: Maestro Fuzz FZ 1B Help
quote:
"There aren't any electrolytics in this thing."
 
 
Are you sure? I found an FZ-1B (Ver.1) schematic on Mark Hammer's site and C1,C2 & C4 (47uF polarized-no specified voltage) sure look like electrolytics. Could be Tantalum I suppose. If so check them for shorts. Check the B-E junctions of the transistors. You should be reading around 0.6-0.7V there. A signal generator and scope could be very helpful, esp. since the two stages are capacitor coupled. Something's not right with that line from the junction of R9/R11 to +9V on the "Hammer" schematic though. That would impose a voltage across both the Ballance and Volume controls, making them scratch and the footswitch pop, as well as shunting the the output signal to ground through the battery. My guess is that the line from C3 to the +9V rail shouldn't be there. This would make Q1 an emitter folower buffer stage feeding a clean signal to the Volume control in "Bypass" mode. It would appear as if most of the distortion is generated by D1 after the signal is further amplified by Q2. Turning the ballance control all the way to the clean side will bring R9 to ground which will reduce overall level slightly but shouldn't turn it off. It will swing R9 to ground in either direction when the pedal is in "Bypass" mode. Double check those caps and the value of R9 (33k).  
 
RE
 
12/16/2003 7:30 PM
Daver
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Rick,  
Thanks for the input. Mark emailed the schematics you mentioned to me. Mine is very different. It has four transistors and a dual 50K pot for the balance. I'm going to draw up a schematic suitable for scanning and I'll send you and Mark a copy.  
Yes there are no electrolytics or tantalums. They are all ceramic discs, none larger than .1uf.  
My meter, I think, is measuring hfe. I have the transistors plugged in correctly. This thing works for the most part, but with the balance past half way or so there is this threshold where you have to hit the string just hard enough to get a loud enough sound out of it. If you let a note sustain it will get to a point where the volume drops quickly to a wisper. I'll get you a copy of the schem and maybe that will help you help me better. Thanks!  
Daver
 
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