Gibson maestro fuzz tone issues

[J M Fahey]

Just thinking aloud:

* soldering is horrible. Cold grainy solder, burnt wires, a solder iron burnt capacitor

* what does "howling" mean?
Do you get oscillation with input shorted and distortion pot set to 0?
You do not but it appears as soon as you rise the pot and/or you plug a guitar there? ... please describe it better. Or upload a video.

* triple check whatīs there against schematic.
Photocopy the one you have, measure voltages on all transistor pins, write them on schematic and upload it.

* in principle howling is feedback and comes from a combination of gain and poor grounding/shielding.
Dead/"bad" transistors will do the opposite: mute the pedal or at least have it show low gain or wonky sound.
In a way, howling means transistors are "too good" or at least "good enough".

* that fuzz is made out of 3 gain stages, which can work on their own, so start by lifting one leg of C3 , inject 100mV 1kHz into Q3 base, listen and scope output.
By the way, howl should have disappeared.

Then reconnect C3, lift one leg of C2, inject audio there, scope its collector and pedal output, has howl reappeared? etc.

2 details: now you have a lot of gain, 2 cascaded stages, reduce signal injected to 10mV and 1 mV as needed with a simple attenuator , say 10k/1k and 10k/100 ohm.
Do not trust original capacitors, use a film or bipolar one, say .47uF or thereabouts to inject signal into following stage.

Then reconnect C2, lift 1 leg of C1, inject there, repeat tests.

Going backwards, you will eventually plug into the input jack, repeat tests.

Somewhere along the way howling must have reappeared, check wiring and grounding; if not, itīs a guitar problem, it feedsback/howls with all that gain.

[shortcircuit]

You have to double and triple check the transistor pinout.

And double check your transistor orientation as far as 1,2,3,Small Bear usually gives you the hfe and placement . Just a thought.

[olddawg]

I know these things are collectible.. but I’ve never used one I liked. The original came a cord with a plug on it hardwired on the output. I always wondered if that affected the functionality when people modified them with another jack. To me... you can MAYBE play an authentic “Satisfaction” riff and that’s about it lol.. The ultimate one trick pony. That said.. I know they can be made to work. I’ve owned several. Again.. as I and others have said... triple check the transistor orientation, resolder everything, check your grounds, and especially if it’s a 60s unit... don’t just assume the caps are all good.

[Leo_Gnardo]

I know these things are collectible.. but I’ve never used one I liked. The original came a cord with a plug on it hardwired on the output. I always wondered if that affected the functionality when people modified them with another jack. To me... you can MAYBE play an authentic “Satisfaction” riff and that’s about it lol.. The ultimate one trick pony.

One of my customers brought me a rusty FZ-1 to repair. It was as you describe, with a "flying lead" for the input. Both pots were shot, and the knobs disintegrated when I pried them off. Volume control had a click switch that disconnects the battery when turned fully CCW. I put in a true bypass DPDT foot switch & replaced a couple caps. Luckily transistors were still good, and the knobs were simply black Gibson knobs like you would find on a Les Paul, no trouble finding replacements. Germanium transistors were still functional, and the pedal runs on a single 1.5 volt AA battery. As you say, good only for the most rancid of fuzz tones - the intro to "Satisfaction" being a prime example. Owner does a lot of studio work and the FZ-1 just one more choice in his library of effects.

[mozz]

Send it over here to PA, i'll fix it. I have made clones of the fz-1 and fz-1a. Any germanium with "some " leakage should work. If the leakage is not high enough it will work but sound gated and choppy. Leakage should be over 250-300, even higher.

Like JM said, post your voltages.

[Enzo]

I recntly had a couple of those in my box. One was real gatey, you had to play aggressively through it. ie. get up to a level threshold.

[pontiacpete]

Just thinking aloud:

* soldering is horrible. Cold grainy solder, burnt wires, a solder iron burnt capacitor

* what does "howling" mean?
Do you get oscillation with input shorted and distortion pot set to 0?
You do not but it appears as soon as you rise the pot and/or you plug a guitar there? ... please describe it better. Or upload a video.

* triple check whatīs there against schematic.
Photocopy the one you have, measure voltages on all transistor pins, write them on schematic and upload it.

* in principle howling is feedback and comes from a combination of gain and poor grounding/shielding.
Dead/"bad" transistors will do the opposite: mute the pedal or at least have it show low gain or wonky sound.
In a way, howling means transistors are "too good" or at least "good enough".

* that fuzz is made out of 3 gain stages, which can work on their own, so start by lifting one leg of C3 , inject 100mV 1kHz into Q3 base, listen and scope output.
By the way, howl should have disappeared.

Then reconnect C3, lift one leg of C2, inject audio there, scope its collector and pedal output, has howl reappeared? etc.

2 details: now you have a lot of gain, 2 cascaded stages, reduce signal injected to 10mV and 1 mV as needed with a simple attenuator , say 10k/1k and 10k/100 ohm.
Do not trust original capacitors, use a film or bipolar one, say .47uF or thereabouts to inject signal into following stage.

Then reconnect C2, lift 1 leg of C1, inject there, repeat tests.

Going backwards, you will eventually plug into the input jack, repeat tests.

Somewhere along the way howling must have reappeared, check wiring and grounding; if not, itīs a guitar problem, it feedsback/howls with all that gain.

Thanks for all this Juan. I had pulled all of the transistors and decided to return it to the shop that it came from until you wrote all of this. Believe it or not I've worked on many of these and have not had this kind of problem and was able to get them out of here within a reasonable amount of time. This time I have 2 of these, the other is an absolute mess compared to this one. No transistors no board just a hand full of components held together with electrical tape. Anyway, you convinced me to give it another go. I'll be back.....
Thanks.

[J M Fahey]

Cool
Worst case, fully rebuild it.
10/15 parts?
One of the few cases where I actually suggest shotgunning, big time

[pontiacpete]

Here it is, completely re-built without the resistors that came along with these transistors(Q1 OC77 Q2and 3 OC75). Checked all the pinouts with the transistor checker. So I think everything is in correctly. I decided to start with the resistor values in the original FZ-1, this is why it's probably not working. But it doesn't oscillate at all when turning the volume pot however there is no distortion or fuzz. It's passing a clean signal only There's -3 volts getting to the collector of Q1, nothing on collector of Q2 , -2.1 on collector of Q3.
Got hit with a lot of amps, this is what I have so far.

[shortcircuit]

Does it pass a clean signal without the 3v supply ??

[pontiacpete]

You mean when the unit is off or the stomp switch, switches off? Yes.
It sounds exactly the same except when the effect is in on position the volume pot does something. Not much a sweep though

[mozz]

First schematic you posted was fz-1a, this is fz-1. There are differences. The resistors from factory and the resistors from small bear are not that far from each other, both will work to at least get some sounds.

If you have no voltage on Q2c, you have wiring problems, open or shorted resistors or caps. Once again, bad transistors or bad pinout.

[J M Fahey]

PLEASE do not say "no voltage" but "0 Volts" or whatever.

IF you meant zero volts on Q2 Collector, first:

If you have no voltage on Q2c, you have wiring problems, open or shorted resistors or caps. Once again, bad transistors or bad pinout.

are quite possible, but also Q2 may be saturated/overbiased.
Notice that Q3 is dropping 0.9V across 10k even with base grounded through 10k and NO bias.

So:
1) check Mozzīs suggestions.
2) remove the 470k bias resistor and recheck.
Please post V-C-E voltages for all 3 transistors.

"Normally" not needed but Germanium is a very crude semiconductor material (and thatīs an understatement) so we must assume *nothing*.

I cringe when I see the DIYAudio people insisting on Germanium "because it sounds like Tubes" and even currently designing a RIAA preamp around Russian Military transistors ... surely that label alone must carry mucho strongo Mojo

[pontiacpete]

Does MEF have a knucklehead ranking? After hours with this thing I notice this is the FZ-1. Says it on the front. Duh. Hence the new schematic.
Anyway moving on, sorry about the vague 'no voltage' reading. I definitely should know better than that by now. How many years have I been reading this forum. Oh only 1 decade.
Here's another, the 470K wasn't 470k but more 470ohms. .. ... .... sorry guys, please be patient.
Now the voltages:
Q1
c -2.9
b -1.2
e -1.1
Q2
c -1.9
b -.06
e 0 ground
Q3
c -1.2
b .5
e 0 ground

It's back to making this really loud whistle as soon as the volume is upped a bit.

thanks
pete

[mozz]

What are your gains and leakages measuring for all the transistors? 470k is the correct value.