Keeley - Fuzz Bender  [traced]

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Motter
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Post by Motter »

This exceptional fuzz is described by Keeley as a Tone Bender with gyrator-bassed active bass and treble controls (purportedly from the Boss MetalZone). It is all SMD except for the two germanium components. It sounds incredible, the EQ and bias controls offering a range of sounds unavailable in other Tonebenders I've played.

I've never done a circuit trace on anything with this quantity of SMD, but I took a lot of photos of the board should anyone want to give it a shot.

I have about half a Gb of photos here: https://photos.app.goo.gl/uVDuzU94ifDBuSiT9

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Post by turbofeedus »

I see he's bought some of those 2SD352B off ebay. I tried some, they were really leaky though. Good to see he's made them work.

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Post by culturejam »

Motter wrote:Tone Bender with gyrator-bassed active bass and treble controls (purportedly from the Boss MetalZone).
Check out schematics for several of the early DOD distortions for more gyrator EQ action. :thumbsup

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Post by modman »

Motter wrote:I've never done a circuit trace on anything with this quantity of SMD, but I took a lot of photos of the board should anyone want to give it a shot.
I have about half a Gb of photos here: https://photos.app.goo.gl/uVDuzU94ifDBuSiT9
Hey, thanks man, but with the great camera you have, the best way would be to use real sunlight and macro function and keep your camera perpendicular to the board. Do this for both sides, so an overlay can be created to see both side of the board at the same time. Then the capacitors don't list values, so may have to be measured; ...

Attachment size limit is 2MB, it should really be possible to reduce size without losing too much of the resolution; looking into automatic resizing of uploaded pictures. If you really like this pedal to get traced, you will have to upload the pics, too many have gone lost because of that

but nice contribution still

input section is probably this:
Keeley - Fuzz Bender
Keeley - Fuzz Bender
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Post by EmmG »

I'm mostly curious about the BIAS control. It's a dual pot.

Is part of it like the ones on pre-MKIII circuits like the Buzzaround and Dizzy Tone which control power to Q3's collector? Or like the difference between the earlier and later MKIII's (sometimes called MKIV) at Q1's base? That change doesn't affect level, but can go from glitchy to smooth. Is it something else?

For the rest of the fuzz portion, we can start with an already drawn schematic and match the parts.

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Post by Motter »

Yeah, not terribly fond of the 2 Mb upload limit. Don't worry, I won't delete the Google album.

Perpendicular board pics would not have been too useful with the pots in the way of most of the circuit. I used the macro lens to try and get the parts and traces underneath the pots.

Not sure I have the tools to measure SMD caps in-situ, but maybe the fancy meter at work can do it.

I'm inclined to take Keeley at his word on this one, considering he pretty much came out and said it's a ToneBender with MetalZone EQ. The dual bias control looks interesting though.

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Post by steben »

culturejam wrote:
Motter wrote:Tone Bender with gyrator-bassed active bass and treble controls (purportedly from the Boss MetalZone).
Check out schematics for several of the early DOD distortions for more gyrator EQ action. :thumbsup
And the Blues Driver ...

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Post by Motter »

With the 47k and 220k coming off the Q1 base, I'm guessing were looking at a ToneBender MK3: https://fuzzcentral.ssguitar.com/3knob.php

Indeed, all resistors on that input stage looks identical to the Fuzz-Central schematic: 47k, 220k, 10k, 10k, 3k3, 100kB Fuzz pot...

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Post by Motter »

Some more notes:

The fuzz pot appears to be arranged as a voltage divider rather than a variable resistor. It has a 1k resistor from leg 1 to ground, and it has a cap across legs 2 and 3.

Treble and bass pots appear to be arranged just like the MetalZone (attached), except: the resistor on Treble leg 2 is 2k4, also the Bass feedback resistor is 2k4.

Still trying to get the coupling between fuzz and EQ
Attachments
Boss-MT-2-Metal-Zone-Schematic.pdf
(383.26 KiB) Downloaded 35 times

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Post by Motter »

Ok I removed the pots and took some top-down photos. I reduced the file sizes to meet the upload requirement. There's some detail lost, but I think they're definitely traceable. Enjoy!
DSC_0044.jpg
DSC_0045.jpg
Resistors:

R01 1004
R02 4702
R03 2203
R04 1002
R05 3301
R06 1002
R07 4701
R08 1002
R09 1002
R10 1002
R11 1002
R12 3900
R13 1001
R14 missing
R15 2202
R16 2202
R17 2401
R18 2401
R19 1003
R20 1002
R21 1002
R22 1803
R23 1803
R24 4702
R25 4702
R26 appears to be a blob of solder bridging two traces

Caps (sorry I don't know anything about SMD caps :oops:, but maybe the descriptions help?):

C01 100u
C02 small w stripe
C03 small tan
C04 100u
C05 medium w stripe
C06 small shiny
C07 small w stripe
C08 10u
C09 10u
C10 10u
C11 small shiny
C12 small tan
C13 small tan
C14 small shiny
C15 medium w stripe
C16 medium shiny
C17 medium w stripe

Transistors:

Q01 M1L
Q02 M1L
Q03 D352

ICs:

IC01 RC4558
IC02 RC4558
IC03 TC1044SE

Diodes:

D01 LED
D02 M7
D05 Ge
D09 missing
D10 missing

Not sure what's going on with all the missing components down by the bass knob. Previous PCB revision or something?

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Post by EmmG »

Thanks, Motter. I did an overlay with the traces on the back.

Bass and treble lugs #1 & #3 connect, as is normal for a gyrator 2 band.
http://www.muzique.com/lab/gyrator.htm

The 2SD352B mentioned upthread is NPN. Is IC3 set up as a voltage doubler for the other IC's?

The "A" row on the gate pot leads to components connected to Q3's collector. The "B" to leads to IC1.
Attachments
Fuzz Bender FSB My trace 01a 20200213.jpg

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Post by Motter »

Looks like IC3 is set up as a simple negative converter from the TC1044 datasheet to provide a -9V rail for the other ICs.

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Post by Motter »

Here's my first stab at it. Let me know if you see anything wonky.
fuzzbender_20200214_1.png
Pretty clever using one of the opamps to increase gain when the transistor gets starved
Last edited by Motter on 14 Feb 2020, 20:57, edited 1 time in total.

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Post by EmmG »

Yes, that's very good as the Buzzaround and Dizzy Tone didn't have normal volume controls. The bias "balance" pot to Q3 had to do double duty and forced you to compromise if you liked a sound that wasn't at the volume level you needed.

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Post by Motter »

Yeah, I'm guessing the weird tapering resistors on the Bias pot are his attempt to balance the starve/makeup gain throughout the range of the pot.

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Post by Motter »

Here's a slightly cleaner version. I think it's easier to read
fuzzbender_20200214_1.png
Using the bass cap values from the Metal Zone's EQ, C15 and C16 (on my schematic) become 220n and 47n respectively. Center frequency is 101.08 (Keeley claims 100 Hz), and Q is 2.98 (http://www.muzique.com/lab/gyrator)

For the treble cap C14, 6n8 is the closest standard value to get Keeley's claimed 10 kHz (actually 9757 Hz).

Using the Fuzz Central Tonebender 3 Schematic (www.fuzzcentral.ssguitar.com/3knob.php) and the Boss Metalzone (and other reasonable guesses*) to fill in the rest of the cap values, we get:

C01 100u
C02 100n
C03 220p
C04 100u
C05 220n
C06 1u*
C07 100n*
C08 10u
C09 10u
C10 10u
C11 500p*
C12 100n*
C13 100p
C14 6n8
C15 220n
C16 47n
C17 1u*

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Post by Motter »

I'd like to amend the above with:

C06 = 2n2

Per the ToneBender3 schematic. This makes sense with R24 and R25 acting as the original ToneBender3's "Tone" knob set at exactly halfway.

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Post by Motter »

Collector voltage with Bias knob down = 1.68 V

Collector voltage with Bias knob up = 0.02 V

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Post by Motter »

Typo in the schematics above. The resistor on the collector of Q2 (R6) should be 10k, not 1k.

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Post by mictester »

C7 is unlikely to be in series with R27 - the first op-amp bias wouldn't happen with the capacitor in the way.
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