Tonebender MK1 help needed!

[carboncomp]

Simple question that I dont think is going to have such a simple answer....but here it goes!

How to I reduce the gating on my MK1?

Love the tone, cleans up a treat and goes uba dark, but just wish there was a little bit more sustain past o'clock.

Q1 80hfe   .70mA
Q2 170hfe .60mA
Q3 160hfe .60MA

[Electric Warrior]

You need to go much lower gain with q2 and q3. With Q2 around 110 I don't have any gating and around 125 I can dial in a very useable amount of gating with the attack pot. Q3 between 70 and 100, depending on how much treble you like..

[LucifersTrip]

Simple question that I dont think is going to have such a simple answer....but here it goes!

How to I reduce the gating on my MK1?

Love the tone, cleans up a treat and goes uba dark, but just wish there was a little bit more sustain past o'clock.

Q1 80hfe   .70mA
Q2 170hfe .60mA
Q3 160hfe .60MA

Adjust the bias better (did you try tweaking the resistors on Q2 & Q3's collectors?)...and post the schematic & Q voltages as noted in:

[peps1]

What EW said!

OR.... if you dont have any other transistors to pick from, as the ones you got where out of range cast off from a friend....

A good fix is adjusting the 180k that connects the Q1C and Q2B to 200k to 510k (you will get less gate the higher you go).

Or tomorrow you can walk up one flight of steps and knock on my door (not early, and bring cake!)   

[LucifersTrip]

what schematic are we referring to exactly?

[peps1]

99% sure he is talking about this layout





and here is a dog in a swing:

[LucifersTrip]

yes, I forgot to mention that the author noted that the 470K should be 180K
http://dam.10.forumer.com/a/posts.php?topic=744&start=0

this is supposedly the earliest version?

[Electric Warrior]

No, this is the latest we know of. There's a schematic of an earlier version with some slightly different resistor values, two resistors missing and an electrolytic instead of the 0.1µF film cap.



We don't have any schematic of the real early vero board version, either:



They might have tweaked the value of the 180k resistor to allow for better bias, but that's just speculation at this point. All of the late units with silkscreened graphics I've seen so far seem to have the 180k. The earlier variant had the 470k.

[peps1]

They might have tweaked the value of the 180k resistor to allow for better bias, but that's just speculation at this point. All of the late units with silkscreened graphics I've seen so far seem to have the 180k. The earlier variant had the 470k.

Trouble is the 180K vs 470K really dose change the circuit dramatically. 180K will give you a synth like heavy gate, and the 470K opens it up to MUCH longer sustain with a fizz decay. and this difference is really confusing people exceptions of how the MK1 Should sound.   

Its interesting that the early ones had the 470K as they were Maestro Fuzz-tone that was modified by Hurst to produce more sustain, then by the time they go into larger production they have moved 180K that sound alot more like the spluttery Fuzz-tone??

That said its not like Iv got a selection of original later MK1 to test out, and there may have been units with 180K with just as much sustain, but im skeptical. 

[Electric Warrior]

Trouble is the 180K vs 470K really dose change the circuit dramatically. 180K will give you a synth like heavy gate, and the 470K opens it up to MUCH longer sustain with a fizz decay. and this difference is really confusing people exceptions of how the MK1 Should sound.  

A good one should have a decent amount of sustain (at least for low Attack settings) and no fizzy decay.
I built mine with an 180k and have no troubles controlling the amount of gating by selecting different transistors for Q2. Getting rid of the fizzy decay on the other hand is pretty hard. Didn't have much luck so far.

[LucifersTrip]

I would be curious to see the schemtic of the earlier one with "slightly different resistor values, two resistors missing and an electrolytic instead of the 0.1µF film cap"

I couldn't find it yet, so if it's readily available somewhere, please post the link

btw...never did let the OP know what the voltages should be for the MK1....and any idea if they're the same for that earlier version with missing transistors?

[Electric Warrior]

This is what I have in my build right now:

Battery: 9V

Q1
C: -8,79V
B: -0,22V
E: -0,24V

Q2
C: -0,66V
B: -0,17V
E: 0V

Q3
C: -8,25V
B: -0,02V
E: 0V

Good sustain at low Attack settings, but it's still possible to dial in some gating. Fizzy decay is not a problem at room temperatures right now. Slightly higher and I have that problem again.


Here's the other schematic:



I'm not sure if it's entirely correct. In the pictures of that unit one can clearly see that the second electrolytic is a 40µF one. Not sure if it's original, though. I know it was repaired at some point.

[LucifersTrip]

Thanx very much for the voltages and the schematic.  The voltages will be a cool guideline. There are just too many versions of those TB's to remember what voltages go with each. I have to make a chart...

I'll definitely screw around with that Hurst TB shortly

thanx again

[Electric Warrior]

Ok, got some new info. They did use several different values for the resistor between Q2's base and -9V, indeed. They just used very funky looking 470k resistors in some units, that don't photograph too well. I know of one (maybe two, I only got a really bad photo of the other) Sola Sound branded unit with a 470k now, one with a 180k and one that has 220 or 270k.
I'll try the 470k tomorrow. Hope that it will help me get rid of that fizzy decay. Will report back with new voltages (Q1 has quite different readings with an OC75. Q2's readings really depend on the Attack pot's setting).

[peps1]

Ok, got some new info. They did use several different values for the resistor between Q2's base and -9V, indeed. They just used very funky looking 470k resistors in some units, that don't photograph too well. I know of one (maybe two, I only got a really bad photo of the other) Sola Sound branded unit with a 470k now, one with a 180k and one that has 220 or 270k.
I'll try the 470k tomorrow. Hope that it will help me get rid of that fizzy decay. Will report back with new voltages (Q1 has quite different readings with an OC75. Q2's readings really depend on the Attack pot's setting).

How have you found the 470K?

With the higher gain TI2G381's Im really feeling the 180K for a nice oldschool usable gate, thought to 390K.

(On a side note the NOS TI2G381 may sound good but they have been a bloody nightmare for quality control, think im going find a substitute for the next batch or just got an email from a part supplier telling me there is a company making 2G381 in the USA if I want to try them on sale or return.)

[Electric Warrior]

Pretty awesome. Much easier to make OC75s work with the 470k. Got a nice range on the Attack knob now. No chirping. Haven't managed to dial in any useable gating so far, though. But I don't think I'll need it. The MKI was about the sustain, anyway.
Focusing on dialing in a good, balanced tone now.

[Dwstanford]

Ive been working on a mk1 off and on for several months now and ive finally reigned it in to what sounds like what i think it should.  Its about 95% where i want it, but i know this is a really testy circuit and i may be being unrealistic about the other 5% .  It kind of reminds me of an old car i used to have that only i know how to start and keep from stalling.  If i have it dialed in just right, it's great, but if i adjust anything, it throws off everything.  Any help would be greatly appreciated.  Ive been working off the sola sound mk1 schematic posted by david main at d.a.m.  Right now, i have transistors as follows:  q1- oc71 (hfe 52), q2- oc76 (hfe 101), and q3- oc75 (hfe 85). Ive tried several different combinations and this one seems to get closest to where i think it should be.  I have very minimal but useable amounts of sputtering or fizzyness, and only with the attack knob at certain settings.  I have a good amount of sustain and some very pleasant gating at some settings.  I still have a few issues, including a bit of gating particularly in the bass range when playing rhythm chords or if you dig and play really heavy.  Its sort of a gate followed by a slower volume swell back to unity gain.  Ive noticed that if you back off the guitar's volume knob a very small amount, the gating goes away, but i lose a bit of bass response.  Overall, that fixes the problem though.  The gating goes away also, if i turn the attack knob down to about 10:30, but again, i lose a bit of bass response.  Also, playing chords sounds a bit quieter than playing lead licks in comparison.  I would expect riffs to sound something like a rangemaster on mid boost setting, but they come across with less definition and volume.  The best way to describe it is less aggressive while the lead licks are super loud and sound amazinig..  Also, i'm getting a little more higher treble in the circuit than i like.  I know this pedal is meant to have a lot of treble, but its so much that sometimes i can hear my pick attack against the strings almost as loud as i can hear a fifth fret A powerchord for instance.  There may be a way to filter off some of the really high end treble while keeping the bite in tact.  Ive come so far with this thing, and im tempted to just hook it up and go with it, but i feel like i can get it perfect with a little more work.

[mac]

You should read this,

http://www.diystompboxes.com/smfforum/index.php?topic=93935.0

Almost the same circuit but at 1.5v
This circuit is very tricky, you need to find the exact germs for each stage. Voltages should be:

vc1: 3-6v
vc2: 3-5v when pot is at 50k; close to 9v when pot is at 0k
vc3: 3-7v

mac

[Electric Warrior]

Why would you have such a low collector voltage on Q1? It connects directly with the battery.

My unit is really well behaved now and it's got a good range on the Attack pot.

Battery measures 9.04 V
Attack at 0:

Q1
C -8.89
B -1.09
E -1.31

Q2
C -8.78
B -0.04
E -0

Q3
C -8.19
B -0.03
E -0

Full Attack:

Q1
C -8.76
B -1.10
E -1.34

Q2
C -5.81
B -0.13
E -0

Q3
C -8.07
B -0.03
E -0

[Dwstanford]

Thanks for the help guys.  I'll do some tweeking tonight and see what i come up with.