Sola Sound Yellow Hybrid Tone Bender

mdc

Active member
Hi folks,

I have one of the yellow hybrid tone benders from Macaris/Sola Sound—curious if anyone is interested in attempting a trace?
It's a fave of Kevin Shields/My Bloody Valentine, and I think it's more closely related to the 3-transistor Supa/Jumbo than the mki/ii/iii TBs.





Unfortunately, it seems like the PCB is attached to the case with some sort of adhesive or something rather than secured by the nuts on the pots. So component side photos are about as good as I can do.

Transistors are a BC109C, a CV10440, and an OC140 Ge.
Markings on most of the components are visible aside from the tiny MLCCs.
If there's interest I can start trying to decipher the resistors, pull voltage measurements, etc.
 

mdc

Active member
Dope!



I can only read the value on one of the three medium sized MLCCs - it's 104 / 100nF; what I think is the part code is visible on all three and it's identical (CX2 9612).

I can see a marking that (I think) reads J G U 0 4 5 on two of the smaller MLCCs, but no values. There are super faint markings that I can't decipher at all:


 

mdc

Active member
The one in the first photo kinda looks like 471 which would be 47pF, correct?

My DMM is very crummy, but here are the voltages for the 3 small MLCCs (9.30 at source):
CCW from top left
L / R
1 - .14 / 2.65
2 - 4.14 / .65
3 - .63 / 4.17
 

music6000

Well-known member
The one in the first photo kinda looks like 471 which would be 47pF, correct?

My DMM is very crummy, but here are the voltages for the 3 small MLCCs (9.30 at source):
CCW from top left
L / R
1 - .14 / 2.65
2 - 4.14 / .65
3 - .63 / 4.17
I should have stated Cap measurement, Can you test for Capacitance on each side of MLCC's, No power connected.
 

mdc

Active member
Unfortunately my DMM doesn’t have a capacitance setting, but this may be a good excuse to upgrade.
 

mdc

Active member
Ironically I splashed out on a DCA55 a few months ago which doesn't measure capacitors either, but oh well.
My understanding is/was that capacitor values are pretty hard to read once the part is in the circuit unless you have a really specific tool, but either way I've upgraded from a $9 DMM to a $30 DMM and I'll see what it can grab later this eve when it shows up.

It looks like there are a couple of differences between that older version and the one I have, aside from the mojo parts — I think that's PNP/OC75 version? Another hi-res shot of the PNP board here: https://live.staticflickr.com/4015/4696792152_7bcc5afd53_h.jpg
 

music6000

Well-known member
Ironically I splashed out on a DCA55 a few months ago which doesn't measure capacitors either, but oh well.
My understanding is/was that capacitor values are pretty hard to read once the part is in the circuit unless you have a really specific tool, but either way I've upgraded from a $9 DMM to a $30 DMM and I'll see what it can grab later this eve when it shows up.

It looks like there are a couple of differences between that older version and the one I have, aside from the mojo parts — I think that's PNP/OC75 version? Another hi-res shot of the PNP board here: https://live.staticflickr.com/4015/4696792152_7bcc5afd53_h.jpg
Yes, Note the lack of 9v Power Jack in PNP versions.
 

Mir9

Member
I showed this image of the board to a Tone Bender/BigMuff fanatic friend and he says it looks like:
-the 1st two stages of a Jumbo Fuzz
-into a Tone Bender MK3 saturation stage.
-then to a Muff type (not TBMK3) tone control, though you can tell us how it operates.
path.jpg

I colored in what I think is the ground. Could you do a continuity check in case I missed anything?
path_ground.jpg
 

mdc

Active member
The tone control has a lot of sweep to it; there's a centre detente in the pot and it's a hpf to the right and lpf to the left a la Big Muff, but the values seem pretty different. It doesn't have the mid scoop and the range seems a lot more dramatic than I remember from the last time I messed around with a muff.

Ground trace looks good and checks out with my DMM. The only thing missing is the wire going to input at the top of the board, which I think also connects to lug 1 of the vol pot.
 

music6000

Well-known member
The Yellow wire on the on the Footswitch should connect to Volume pot middle lug which is Out from PCB ?
 
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mdc

Active member
Yellow wire from vol lug 2 to footswitch is correct.

New DMM showed up, but the capacitance measurements are all over the map unfortunately. †he medium sized cap on the lower right is reading a clean 100nF, which gives me some confidence that all three similarly sized caps are 100nF which would imply that they're the coupling caps between stages, perhaps? Pretty sure those are usually 100nF on most benders and variants.
 

Julian A

New member
Hello all! I was just made aware of this thread. I "traced" and built this circuit a couple years back based strictly on photos, and have amassed some info and a bunch of photos since then. I've never handled this pedal, and OP has one + great photos, which is the best resource!
Been dying for confirmation on the potentiometer values. I currently run 10K tone and 100Ks for vol/fuzz, but they could all be 10K. I think I've even seen a 50 before.

I made a schematic while first attempting to trace it, and I believe the overall layout is correct, however, it is kinda a mess due to the various values I've seen on the multiple versions of the pedal. A couple of missing/speculated/wrong values as well that I didn't know at the time.
The "probably 5V zener" was a complete guess at the time, but more recently in a photo, I saw the BZX and what looked like a 4, and also found this webpage which mentioned dropping the battery voltage to 4.7V. (page translator needed unless you know French) https://www.mxv.be/2019/01/sola-sound-yellow-hybrid-oc140-tone-bender/

so perhaps a 4.7 BZX diode. I used a 5.1 back in Jan 2019, works for me.

Also made a vero layout for my build, which I have somewhere. Probably not the cleanest layout, but ey it works. IIRC I vaguely based it on the tagboardeffects Jumbo Tonebender
 

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Julian A

New member
For the little snubber caps, I've confirmed 470pF on one unit. This one was listed as a "first run 2000s" and the box even says first run. It has the zener circuit and is NPN. I assume it's the first run/proto of NPNs with the nkt214, and was made in the 2010s.
 

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