Tonebender MkII questions

[blanik]

i made a Tonebender MkII on my breadboard and been playing with it for a while now, the Ge transistors read 70Hfe-70Hfe-100Hfe not leaking AFAIK (steady reading on the DMM), i initially used a 0.01uF as input cap but when i use a 4.7uF or 5uF electro like on the original design it "gates out" if i'm picking hard but what i'm wondering is when i put the electro like on the fuzzcentral schem, positive side on guitar input almost no sound comes out, i have to reverse it to sound "normal" ?

(and even with the regular 4,7uF value, i doubt the gating was normal on the initial design, i'm using a Dimarzio ChopperT (9,9 Ohms) so it's not super hot output, i'm skeptical that a 60s Les Paul had a lot less output than that and yet the pedal is unusable with the 4,7 uF....)

second question: i didn't have a 100k pot for volume so i used a 1M one but if i lower the volume a little bit all the highs disappear, i guess when lowered the volume acts like a tone control but on guitars the higher the volume pot the more highs come through?

[foxfire]

are you using a trim pot or 8.2k resistor to bias Q3? if you're not using some sort of trim pot there i would strongly suggest you do. i just reboxed my B.Y.O.C. tone bender and added a switch for either a 0.047µF or 10µF input cap without any problem. as you having to reverse your polarized input caps, i don't know.

[Solidhex]

Yo

  Yeah gating is usually a symptom of misbiasing. Check the voltage on the collector of Q3 and get it near -4.5v with a 9v supply either by using a trimpot or use a pot temporarily them put a fixed resistor with the tweaked value.
  You should put a 100kA for the volume control like the schem. You need a good amount of highs or else you'll lose all the texture of the fuzz.

--Brad

[blanik]

yeah, i used a trimpot, trimmed to 4.5V on Q3, the fuzz sounds great with the small input cap but i doubt the original effects (with the 5uF input cap) would gate like mine, if i pick hard the signal clamps down and comes back as the chord decays... but the bias is ok... :-S

with the 1M volume i don't have any choice than leaving all open otherwise i loose all highs right away...

[yeeshkul]

Bypass the volume pot (input and output lug, not the ground lug) with something like 2n2 cap. Solder it right on the pot lugs. That helps to keep trebles with the volume down.

[Electric Warrior]

according to David Main (d.a.m.) Q3's collector voltage was way higher on the originals he measured.
a steady reading on your dmm does not indicate a non-leaky device. build R.G.'s germanium transistor test circuit to measure your transistors.
the orientations of the electrolytics in that schematic are correct.

what type of germanium transistors do you use?

[yeeshkul]

according to David Main (d.a.m.) Q3's collector voltage was way higher on the originals he measured.

can you give us a link please? or do you remember what was the typical voltage on Q3C?

[Electric Warrior]

http://stompboxes.co.uk/forum/viewtopic.php?f=6&t=897&p=13746&hilit=Q3+bias#p13746
http://dam.10.forumer.com/viewtopic.php?t=779&highlight=voltage

[blanik]

according to David Main (d.a.m.) Q3's collector voltage was way higher on the originals he measured.
a steady reading on your dmm does not indicate a non-leaky device. build R.G.'s germanium transistor test circuit to measure your transistors.
the orientations of the electrolytics in that schematic are correct.

what type of germanium transistors do you use?

i just read the post where he states his Vox MkIII has 7.9V at Q3..!

i use Small Bear Ge PNP i can't see the number or brand on them, Q1 and Q2 read 70 and Q3 100

[Electric Warrior]

ok, the transistors should be fine. but as long as you don't have actual OC81D transistors you probably shouldn't use that schematic.

this one works great for me, my (OC75) transistors are roughly in the same gain range as yours.:



I've compared pictures of many vintage Sola Sound/Vox/Marshall Supa Fuzz units for this one... so it should be fairly typical.

[Sir H C]

ok, the transistors should be fine. but as long as you don't have actual OC81D transistors you probably shouldn't use that schematic.

this one works great for me, my (OC75) transistors are roughly in the same gain range as yours.:



I've compared pictures of many vintage Sola Sound/Vox/Marshall Supa Fuzz units for this one... so it should be fairly typical.

So you use a 10k to ground for Q1's base and not the 100k he has?

[Electric Warrior]

yes. from what I know this is being considered typical for the OC75 version. same for the 47k resistor at Q2's collector.
hard to tell about the 10k (sometimes 12k) from most circuit board pictures, because the transistor is blocking it from sight. there is photographic evidence of the 10k, however. just search the d.a.m. forums. greatest place for MKII information.

[Sir H C]

yes. from what I know this is being considered typical for the OC75 version. same for the 47k resistor at Q2's collector.
hard to tell about the 10k (sometimes 12k) from most circuit board pictures, because the transistor is blocking it from sight. there is photographic evidence of the 10k, however. just search the d.a.m. forums. greatest place for MKII information.

greatest source of Tonebender information in general. 

[Electric Warrior]

for sure! and vintage pedal porn in general - thanks to Graham!

[petemoore]

  Q2 and Q3 of the Tonebender = Fuzzface, biases like a fuzzface, iow some transistors might bias nice with an 8k2 collector resistor.
  Voltage measurements, transistor with ballpark gain and low leakage [see GEO]. The numbers printed on the transistor don't really mean it's a suitable candidate or not at this point.
  Rebias w/transistor swap.

[Electric Warrior]

Tried that, lacks character.

[petemoore]

  Tried that, lacks character.
  What's 'that' ?

[Sir H C]

for sure! and vintage pedal porn in general - thanks to Graham!

A new guy just showed up who had the most amazing pedal collection photos.  Jaw dropping.

[Electric Warrior]

yes, unbelievable 

  Tried that, lacks character.
  What's 'that' ?

biasing it like a fuzz face.

[yeeshkul]

I can't see the point? FF is almost the same thing ini? The factory produced Ge FF were not adjusted to -4.5V bias either ...
We know the sound of Tonebender from variety of famous records, that's the real reason we like TB. The question is if those units were stock or modified. If they were stock then yes, 6.5-8V bias but .... Probably the best thing is to put trimpot + an aditional pot to the c3 and bias it by ear