Hi all,
I wanted to share this and get any feedback from the fuzz experts here... This is my attempt at the original layout for the Sola Sound Tone Bender Professional MKII.
I think I hit it spot on. Please share your thoughts.
(http://i243.photobucket.com/albums/ff145/helpmechris/cb_tonebender.jpg)
When I build I am going to replace 8k2 with a 470 ohm wired to a 20k trimmer jb-welded to the back of a 5K pot... for internal and external bias network, however for now I just want to focus on getting as close to the original layout as possible.
Regards,
Chris Brown
Here are some close-ups of an original stripboard layout, including underneath the board shots that might help. Scroll down near the bottom for the pics.
http://dam.10.forumer.com/viewtopic.php?t=502&start=45 (http://dam.10.forumer.com/viewtopic.php?t=502&start=45)
Awesome, Tonight I'll incorporate the differences that I see and update the layout. Thanks very much for the helpful link... I googled for a long time trying to find a shot of the solder side... that's exactly what I've been needing to see.
I was able to make some changes based on the link posted by tatter.
The spacing between C5 and C6 seems to be different between the different versions (marshall, roto, etc etc) and some also have an added 100ohm resistor to the right of C6.
Here's what I hope is the final version:
Any input is appreciated. Have fun :)
(http://i243.photobucket.com/albums/ff145/helpmechris/cb_tonebender_layout.gif)
Hi!
R2 was 10K or 12K on originals with OC75 transistors (10K versus 100K makes a lot of difference). R1 sometimes 12K. R3 47K on pedals featuring OC75's.
The values you specify was used on pedals featuring audio drivers (OC81D's) The limiting resistor you mention (100 ohm) was used on some early supa fuzzes...
Layout looks good, though..! :)
Kenneth
here's one with more realistic part sizes and different resistors, according to kenneth:
(http://www.naturalbornyoers.com/forumpics/mk2layout.png)
layout works.
Just built this, sounds awesome. I used OC75's for Q1 and Q3, and an OC76 for Q2 (it sounded better than the OC75 I had for Q2).
(http://i260.photobucket.com/albums/ii8/sharkminusbear/DIY/IMG_0165.jpg)
It sounds better than the BYOC I built, there's less noise, and the attack control is very useful (unlike the BYOC). Not to hard for a beginner.
I bet it was a lot cheaper than the b.y.o.c. as well :D
Funny I was just finishing up a Bender with this layout and I have one of those huge Mallory 150 .1uf caps on my board too :icon_mrgreen:
I bought some orange drops just for kicks and the .1uf is as big around as my thumb. It would dwarf everything else on the board.
I used Vishay MKT1813 in mine.. a lighter shade of yellow ;)
(http://img.photobucket.com/albums/v697/nitefly182/P1010099.jpg)
nice job ;)
Why not shorten the leads on the transistors? The emitters are especially susceptable to noise if you have no emitter degeneration.
Quote from: Cliff Schecht on February 09, 2009, 01:53:58 AM
Why not shorten the leads on the transistors? The emitters are especially susceptable to noise if you have no emitter degeneration.
I've never had any problems. However, I just finished this build and using the trim pot I can only adjust the voltage within an extremely narrow range from about 9.22 volts to 9.35 volts. I skipped the bias mod and just used the trim on the board and I dont know whats up. Two lugs of the trim are tied to one strip and the remaining leg is at the other strip. It should be working perfectly but its just not altering the voltage. I dont know whats up but its pissing me off.
9.22 - 9.35 on Q3C?
What value is the C resistor and what value is the trimpot and vhat voltage is on your battery lugs?
What is the Hfe and leakage current of Q2 and Q3?
This happened to me also and i had to use 50k trimpot to balance the voltage - it very depends on the 2nd and 3rd tranny leakage/Hfe..
Quote from: yeeshkul on February 09, 2009, 02:52:55 AM
9.22 - 9.35 on Q3C?
What value is the C resistor and what value is the trimpot and vhat voltage is on your battery lugs?
What is the Hfe and leakage current of Q2 and Q3?
This happened to me also and i had to use 50k trimpot to balance the voltage - it very depends on the 2nd and 3rd tranny leakage/Hfe..
I just tried dropping a 50k pot in place of the bias resistor and was only able to get the bias down to 9v. The transistors are a tonebender set from small bear so the leakage should be reasonable although I dont have leakage measurements. Im using a power supply and a 50k pot for the bias resistor right now.
what resistor did you use in Q2 collector? People refer finding 47k in devices with OC75s. The thing is that the bias voltage of Q3 quite depends on collector voltage of Q2.
Q2 leaks -> there is voltage on RC2 => this make voltage on Q3B (Vcc - VC2) => this makes voltage on Q3E (VQ3B - 0.2V ish).
Then Q3C quite depends on how strong is the divider RQ2C/fuzz pot.
EDIT: RC2 down -> VRC2 down -> VC2 up -> VB3 up -> VE3 up -> VC-E down down => VC3 down
Quote from: yeeshkul on February 09, 2009, 03:15:22 AM
what resistor did you use in Q2 collector? People refer finding 47k in devices with OC75s. The thing is that the bias voltage of Q3 quite depends on collector voltage of Q2.
Q2 leaks -> there is voltage on RC2 => this make voltage on Q3B (Vcc - VC2) => this makes voltage on Q3E (VQ3B - 0.2V ish).
Then Q3C quite depends on how strong is the divider RQ2C/fuzz pot.
I used a 47k resistor for the Q2C and for some reason the voltage at Q2C is only 150mv. Its supposed to be about 1v right?
i've just measured half a volt on mine. i use top quallity matsush*ta trannies. they have very small leakage current so that's why. if your Q2 is leaky the low voltage makes sense.
Q2 leakage curent up -> VRQ2c up -> VQ2C/VQ3B down
EDIT: let me check out some leaky Czech OC75 for Q2. I write back soon.
The word (well, company) Matsushita gets edited. :icon_lol:
yeah, that's what i expected. After inserting an old Czech OC75 with massive leakage for Q2 the VQ2C vent down to 250mV and VQ3C went up for almost 3 volts.
Matsupoota rulez!
actually i made a little testing board for FF/TB circuits with bunch of trimpots. I will make a separate thread out of it, i see it makes sense. Especially if you are up to building more than one unit.
So you think the transistors are crappy? I figured the small bear stuff was the best way to go for something like a tonebender but I guess not. So based on what you are saying, I need to reduce the Q2C resistor and crank up the bias resistor in order to get those voltages around 1v and 4.5 volts for Q2 and Q3?
I am not saying anything like smallbear stuff is crappy. I have really great experience with that shop. The guy behind it is an extremely helpfull man. Leaky transistors can bes used in TB circuit. The originals were leaky as well i bet. Q1 even must be leaky to bias itself. Just use 47k for Q2C and bigger trimpot to push down the Q3 bias (to at least 7V) and rock on ;D.
EDIT: measure the trannies, put the results up here and i will tell you the possible best choice for the setup.
Im about to give up. I have built two tonebenders and none of them would bias up in any way. I cant get anything good out of this pedal and its exactly like the layout posted about halfway down the first page. I dont know what it is but I just cant make a tonebender work for some reason. The only change I made was putting a trim pot in place where the original pedals had an 8.2k resistor so I worked around the bias mod on that layout. All the wiring is exactly the way it should be. I just dont get it.
did you connect the bias 2 and bias 3 traces? or did you lay it out like in Chris first layout?
edit: oh, I can see from your picture that you did it the right. don't give up. you've got such a neat looking board..
maybe it's the trim pot. try to connect only two legs.
Nitefly if you can'y reach 4.5V at Q3C even with 50k trimpot, there is something else that must be wrong. Leaky electro cap? Did you measure them? Cold soldering spot? Measure everything first. Post the voltages.
By the way i posted my test circuit here http://www.diystompboxes.com/smfforum/index.php?topic=74130.0 (http://www.diystompboxes.com/smfforum/index.php?topic=74130.0)
Don't give in without the fight :) Man i was so many time right on the edge of throwing that bloody thing out of my window and it always turned to be fine in the end. I am talking in general now. It is gonna be fine, TB is too simple not to come out right.
Nitefly, your build puts mine to shame, your's looks awesome.
I used a 25k linear pot for my bias and I was able to get the collector on Q3 (OC75) to around 4.5 easily . I happen to like it biased differently depending on how I feel though... sometimes I got for a higher bias.
I ordered the tonebender set from smallbear and was not impressed with the combo, it sounded too smooth and modern for my taste. I ended up using one of the OC76's they sent me in Q2, but I salvaged 2 OC75's from my BYOC. It's got this nice gorwling breakup now with that sweet germanium sounding decay on notes.
If you can't get the bias below 9v with a 50k pot, then I think something else is going on.... oh hey, you said all you did was put a trimpot in place of the 8.2k? I put a 470R resistor there and then used the bias pot method from Electric Warrior's layout. Maybe you could throw a 470R in there and just connect the leads of the trimpot with wires from the bias strips on the board?
Dunno if this is right or wrong, I'm new at this stuff.
Quote from: sharkminusbear on February 09, 2009, 08:45:51 PM
Maybe you could throw a 470R in there and just connect the leads of the trimpot with wires from the bias strips on the board?
470R is there already ini? That one is supposed to be there all the time and people just change it for 1k when the want more volume out of the device.
Nitefly check out if the trimmer used is connected well (one side right to the collector and the other side to the 470/10n junction). Also check out if you used the right trimmer legs and measure the trimmer. Measure anything you wanna solder up - that is my general advice.
Or maybe send a picture of the solder side.
ah i see what you mean, i checked out the picture way above here. The another - "bias" - 470R is not necessary unless you wanna some sort of a permanent bias pot on your stompbox.
one more thing - make sure you measure the C3 voltage right on the Q3C leg and not on the bias trim/470/10n output junction - this spot is always high(!).
I was measuring the bias at the Q3C solder joint. Ill take measurements and reflow every joint and take a solder side photo in the morning. Thanks for the help guys.
OK. I plugged it in today to take measurements and it miraculously was able to bias up to 4.5v on Q3C. There is almost zero output volume though. Could the low q2 voltage be causing the volume issue?
Q1C - -8v
Q2C - -229mv
Q3C - -4.5v
(http://img.photobucket.com/albums/v697/nitefly182/P1010103.jpg)
(http://img.photobucket.com/albums/v697/nitefly182/P1010102.jpg)
did you use a 1k (or is it 10k? hard to tell) resistor instead of the 470R on purpose?
Quote from: Electric Warrior on February 10, 2009, 02:38:09 PM
did you use a 1k (or is it 10k? hard to tell) resistor instead of the 470R on purpose?
Thats what was on my schem from small bear. If anything I've heard that should increase the overall volume of the pedal.
otherwise it looks great. have you checked for solder bridges?
here's a new version of the layout with switch and pots. hope it works, any input appreciated.
(http://www.naturalbornyoers.com/forumpics/ToneBenderMKII.png)
"here's a new version of the layout with switch and pots. hope it works, any input appreciated."
nice job man :)
As for the 1k - yes it helps with volume boost. It is a collector resistor so the bigger it is the more volume you get (U=R*I). The other collector resistor(bias) is pushing on the output voltage from the other side, that's why is this unit normally so quiet - you can hear how the volume changes when you tweak the bias trimmer. I am using 1k5 in my units. The impact on the tone is about the same as swapping that 100k res to 47k = nothing. On the other hand, very remarkable impact on the tone has the Q1B resistor. If it is too small (10k) then the first tranny doesn't get enough bias voltage and the fuzz is weak (about like Fuzz Face). If you use 100k you will get insanely wild fuzz. That's why they went for 100k in later releases.
I tested everything i say here by ear on my test board this morning. So no funny stuff :)
Can you please tell me what voltage range you get now on the Q3 collector after changing Q2C res to 47k?
I think the 100k is a OC81D version thing. The late pcb Supa Fuzzes still have a 10k.
sorry, yes you are right :) - basically the leakier tranny you use for Q1 the smaller the resistor can be.
My build matches the most recent one posted except the 470 ohm resistor is a 1k and the 25uf cap is a 50uf according to the small bear schem. Thats just a power filter cap though so it shouldn't be a big deal.
the power filter cap varied a lot in vintage units...
OC81D version:
(http://www.naturalbornyoers.com/forumpics/ToneBenderMKIIOC81D.png)
very nice again!
I use 25k bias trimpot and 25k pot in series in my builds. First set the pot to the middle position and adjust the trimmer so there is 4.5V at collector. Then you can tweak the pot both ways over the full range of the sounds: gated - proper smooth - smooth and louder.
5k pot &bias res are fine to balance the temperature caused bias changes though.
thank you!
compensation for temperature related bias changes is exactly what I'm aiming for. but I have to admit a wider range can be very useful..
Hi everybody. I tried to build my own MkII ToneBender Professional but something it's not working. Before checking the components (maybe the transistor are gone!) I'd like to check the wiring if you can help me. I put a picture of the wiring I chose.....
Thanks for help, Andrea
http://www.megaupload.com/?d=U2ESAAL8
Hi everybody,
Any reason too put the 100k resistance in diagonal like this,or it's just for the reading ?
To keep the resistor flat while still using two adjacent traces. :)
Ok,thanks !