Boss TR2 (...only a mini problem for Profi's)

Discussion in 'The Projects Forum' started by jjj, Dec 17, 2008.

  1. jjj

    Thread Starter Senior Member

    Feb 25, 2007
    111
    0
    Now, when I press the tremolo effect pedal, it goes on; than I have to press the pedal again to turn it off.
    I want that it only triggers the tremolo effect for as long as I press down the pedal.
    http://img123.imageshack.us/img123/6985/tr2vj0.png
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    It can be done. How comfortable are you with making an extensive modification to the insides of the tremolo box? You will also need to get a foot pedal with a non-latching single pole double throw (SPDT) function, and change the input connector.

    What you would be doing is cutting the leads from the flip flop to the two gating FET's. The gates would be pulled up to +9 volts with 1 M resistors, and the new pedal switch would alternately pull one gate to circuit ground.
     
  3. jjj

    Thread Starter Senior Member

    Feb 25, 2007
    111
    0
    Hi beenthere,
    It can be done.
    I know these two Fet's are switches, but I'm not sure which one is on while the other is off or both on/ both off...? As a hobbyist, I usually fiddle with a high Ohm resistor or small cap to find out and then I discover what's going on. :) Why/what are the two FET's switching?
    From what I gather: the upper FET bridges the effect and the lower FET turns the effect on. That means the upper FET has to be off, while the lower FET is on and visa-versa. (?) Am I ...guessing right?

    How comfortable are you with making an extensive modification to the insides of the tremolo box?
    No problem with that, because adding 2 x 1M and and changing that SW shouldn't be a problem. I have 50 years of "electronics fiddle practice".

    You will also need to get a foot pedal with a non-latching single pole double throw (SPDT) function, and change the input connector.
    The Boss Tr2 is a pedal !! http://www.zzounds.com/item--BOSTR2

    What you would be doing is cutting the leads from the flip flop to the two gating FET's. The gates would be pulled up to +9 volts with 1 M resistors, and the new pedal switch would alternately pull one gate to circuit ground.
    Please check my altered diagram... Is that what you mean?

    http://img218.imageshack.us/img218/2123/tr2modifiedly5.png
     
    Last edited: Dec 17, 2008
  4. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    That is the modification. You have a probability of .5 in getting the switch function correct the first time. If it's tremolo all the time until the switch gets depressed, swap the leads.

    You might have to replace the switch currently in the Boss Tr2. Your drawing of the switch needed is correct.
     
  5. jjj

    Thread Starter Senior Member

    Feb 25, 2007
    111
    0
    Thanking you for your help...! See, even a young bugger like me (67) is still ticking alright! :D
    I just wanted to be sure, because now that you explained it... the coin gradually dropped. It's better to know what I'm doing. So, Thx again. :)
     
  6. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Nice not having to draw it out.
     
  7. jjj

    Thread Starter Senior Member

    Feb 25, 2007
    111
    0
    Great... but as usual one never gets enough of good things:
    Now I wished the tremolo would not come in that sudden, but gently or with a fast, but gentle volume rise/ delay. Like that: <
    Maybe that can be done by just adding a little Cap or Electro and a bleed resistor on the right spot? Do you think that is possible? Where would be the best spot? (In the effect path, between R24 and Q3 ??)

    [​IMG]
    [​IMG]
     
    Last edited: Dec 22, 2008
  8. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Arguably the easiest and best way to do that would be to modify a volume control pedal to replace VR3, with the volume pedal also incorporating your new effect on/off switch as a microswitch with a lever.

    This would provide you with smooth and exact foot control over the depth of the tremolo. Otherwise, you'll have a dickens of a time trying to get an automatic effect timing/depth worked out for general use.
     
  9. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Your second image did not come up because of errors. It should work to place a capacitor to ground between the 1 meg resistor and the diode. That will slow the effect coming on. A resistor in the path to ground (something like 470K) should slow the other shutoff.

    You may need to get several capacitors in the range .1 uF to .001 uF and experiment to see which one works for you.
     
  10. jjj

    Thread Starter Senior Member

    Feb 25, 2007
    111
    0
    Thanking you for your great help... kind beenthere and SgtWookie,
    [​IMG]
    [​IMG]
     
    Last edited: Dec 27, 2008
  11. jjj

    Thread Starter Senior Member

    Feb 25, 2007
    111
    0
    Since I'm using this tremolo pedal with both hands busy on a Synth, I can only activate the tremolo via the Boss pedal. That's now working as I wanted it.

    To get a gentle tremolo start, instead the sudden one I get now, I tried your idea with Caps to ground, but it only works one time or when the Cap is again fully earthed out, because once the cap is charged there are no delays anymore.
    Actually, looking at the circuit: the Input is is going via bypass straight to Output. That means the volume could be controlled there, but how?
    All I would need is a fraction of volume attenuation.
     
  12. jjj

    Thread Starter Senior Member

    Feb 25, 2007
    111
    0
    (Please see circuit on page 1.)

    I'm still at it to get a gentle delay at the start of the tremolo effect and trying to understand what's going wrong:

    When I put a 1MF Cap onto between D2 and R24
    to ground, I get quite a strong delay, but that only works the first time. After that the Cap is saturated and doesn't discharge. Only after I earth out that Cap I can repeat the delay.

    Actually, I cannot understand why the Cap doesn't get discharged, because when the pushbutton is not activated the collector of Q7 is earthed out or grounded. So, that should also ground (or empty) the Cap. Why does it not??

    Does it mean... there must be some voltage, but then again, how come it turns off JFET Q1 ???
     
  13. floomdoggle

    Senior Member

    Sep 1, 2008
    217
    2
    Hey JJJ,
    Try a phase shifter in front of the tremolo to get the "slow" rise effect. What sound are you trying to duplicate? A Wah-Wah pedal in front, which would be what Wookie wrote, could give the same effect if used as a volume control. You might also try a ring modulator.
    Dan
     
  14. jjj

    Thread Starter Senior Member

    Feb 25, 2007
    111
    0
    Thanking you for all the good advice!!! :)
    Yes, I guess I'll close up the Tr2 and let it go, because I want to build this Morley Volume pedal for which I have the circuit. So this might do the trick...
    Besides... if anyone needs MIDI Merger, there's a damn cheap way of getting there.
    The circuit is amazingly simple! Just get the (PDF) circuit, here: http://www.ucapps.de/midimerger/midimerger_pic16f88_to_core.pdf
    and buy their ready programmed PIC 16F88 for 5.70 Euro here: http://www.mikes-elektronikseite.de/shop_deutsch/index.htm
     
Loading...