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Fulltone Fulldrive 2 guts

11/24/1997 10:25 AM
John Greene
Fulltone Fulldrive 2 guts
Does anyone know what a Fulltone Fulldrive 2 is made of? I was going to attempt to trace one through but I am told that much of the circuit is covered in gumpucky.  
12/2/1997 12:54 PM
John Greene

Well, I got my hands on one and tried figuring out just what was going on inside and finally gave up. There was just too much of the goop all over to be able to tell what was going on. So, I shelved it and moved on to other things.  
As I was cleaning my desk I found a fuzz face schematic I printed, the fulltone 69 schematic and a copy of the TS-9 schematic. I did a double take at the TS-9 schematic. I noticed the output was exactly like the fulldrive 2, then I noticed the tone control was exactly like the fulldrive 2, then I noticed the input was exactly like the fulldrive 2. Hey, the fulldrive 2 is really a modified TS9 with true bypass. Who would've thought!  
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12/2/1997 4:46 PM

>>Hey, the fulldrive 2 is really a  
>>modified TS9 with true bypass. Who  
>>would've thought!  
Now you've done it!! Just think of all those Fulldrives that are about to give up their lives in the pursuit of science!!
12/2/1997 7:35 PM
Jim S.

I'm not too surprised. The TS9 and the Fulldrive seem to occupy the same sonic ballpark. The Fulldrive is advertised to feature asymmetric clipping, so I would expect to see its clipping diodes be purposefuly mismatched. I'm sure there are other differences as well, since the Fulldrive has way more gain capability and also features the fatter boost mode.
12/3/1997 12:04 PM
John Greene

The differences from the TS9 that I can figure out without removing or unsoldering anything are as follows:  
The cap in the tone control is a .33uF instead of a .22uF  
The 'Drive' control pot is a 250K instead of a 500K.  
The wiper of the Drive control is connected to the pole of the 'Boost' switch.  
The 'non-boost' setting connects the drive wiper to a 22K resistor (51K on the TS9).  
The 'boost' setting connects one end of a 1Meg pot (boost control) to the wiper of the overdrive control. The wiper of the boost pot is always connected to the 22k resistor. The boost also has a brightness cap connected between the wiper and the end connected to the switch. The value has been painted over and I can't measure it without removing it. There is also a larger electrolytic cap connecting the end of the boost pot to the wiper of the overdrive pot. When the boost is enabled, this cap is shorted. I think it's to keep noise from being coupled in through the 1Meg pot when the boost is not enabled.  
The 4.7K->.047uF (TS9)series circuit connected the inverting input of the clipper has a 3.3K resistor instead.  
Everything else is the same as far as I can tell. I couldn't measure the .047uF cap(TS9) or the .22uF tant before the tone control but it is a tantalum capacitor. I also couldn't measure the 51pF accross the diodes. I did verify the input cap to be a .02 though.  
The diodes do look like silicon diodes (.7 volt drop).  
The opamp is an 8pin DIP package, no idea what brand or part number but I doubt he's ordering vintage parts form surplus shops in Japan. ;)  
12/3/1997 12:08 PM
John Greene

Oh yeah, the transistor on the input is different than the one driving the output.  
12/6/1997 9:14 AM
dave chun

Any idea as to the function of the pull-up volume knob (the one that "removes most of the compression from the circuit...")?  
Does this just double the voltage in places (sending 9V to 4.5V inputs) to increase the headroom? (Or are you working with an old FD2 without this particular feature...?)
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