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Fulltone Full Drive 2 -> Bass Drive

isher1992

isher1992

Nov 27, 2008
1,209
200
Little Rock, Arkansas
#1
So, I bought a FD2 because I refuse to pay 300.00 for a Bass Drive MOSFET when I can mod the FD2 MOSFET to the same thing and only spend 80. I know there are four capacitors that are changed in the circuit, but I am having some difficulty figuring out just where they are on the PCB.

I know the two ceramic caps are C1 and C5, C1 becoming 51pF and C5 becoming 100pF.

fulldrive.jpg


C5 on this schematic is also what needs to be changed, but I'm difficulty narrowing it down to what that correlates to on the Fulltone PCB. I'm not sure this schematic is entirely correct either.

Any knowledge as to what the last two capacitors that need to be changed are is greatly appreciated. :)
 
#5
isher1992 said:
No problem, trying to work on it now. It's almost impossible to take the PCB out so trying to work on it from the top side rather than desoldering.
Click to expand...

If this model is constructed like the Bass-Drive, removing the board should be fairly easy. But you'll have to remove everything, or at least get to where you can tilt the board towards you. Removing it all is safer, since it lets you work without obstruction or needing to keep the board propped.

Good luck!
 
#7
Confirming that it works, it is now the Bass Drive.

However, one thing I will suggest is to change the 1N914 in the Silicon clipping section to a 1N4001. Also, it still seems to lose some lows like the Bass Drive does, so the input capacitor (not the ceramic, but the one following it) could be upped to 0.047uF or even 0.1uF.

The Ibanez PD-7 is a similar schematic, so I wouldn't be too surprised if the 0.1uF input would be better.
 
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#9
Dave W said:
I'd love to mod by BassDrive to not lose any lows. One of these days...
Click to expand...

By looking at the rest of the circuit, the coupling caps are all pretty large (1uF) all the way to the output cap. I would imagine any low end loss is right at the beginning, which would be the first 0.022uF cap. There's also a cap right after the volume that's 0.01uF that might could be changed to 0.022uF as well.
 
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#10
I will say, working with Fulltone stuff has shown me a lot of their marketing overhype... like for example, saying they use "authentic, NOS" JRC4558's...

...when the actual part is stamped KA4558P, which would be Fairchild's replacement for the same chip. An authentic JRC4558 would be stamped JRC4558 and nothing else. The new NJM4558 is the same company.
 
#11
isher1992 said:
Confirming that it works, it is now the Bass Drive.

However, one thing I will suggest is to change the 1N914 in the Silicon clipping section to a 1N4001. Also, it still seems to lose some lows like the Bass Drive does, so the input capacitor (not the ceramic, but the one following it) could be upped to 0.047uF or even 0.1uF.

The Ibanez PD-7 is a similar schematic, so I wouldn't be too surprised if the 0.1uF input would be better.
Click to expand...

Nice. Congrats! Thanks.
 
#12
isher1992 said:
I will say, working with Fulltone stuff has shown me a lot of their marketing overhype... like for example, saying they use "authentic, NOS" JRC4558's...

...when the actual part is stamped KA4558P, which would be Fairchild's replacement for the same chip. An authentic JRC4558 would be stamped JRC4558 and nothing else. The new NJM4558 is the same company.
Click to expand...

:laugh:

Any hype and well-documented behavioral issues aside, Fuller did make some very nice pedals. Don't get me wrong; I'm no apologist for the guy. I'm only giving him credit for what he did do well.
 
#15
isher1992 said:
Got it!

C1 - 10pF -> 51pF
C5 - 51pF -> 100pF
C7 - 0.068uF -> 0.33uF
C8 - 0.22uF -> 0.068uF
Click to expand...

Waking up a zombie thread! I have done the first half of the mods i.e. the ceramic caps C1 and C5, mainly because if you're careful you can do them without taking the board out. The result is a lot more bass than before but still a slight loss, which is good enough for me. I have two identical FD2 CS models with close serial numbers and A/B-ing them really shows the difference.
 

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