Replacing a flip flop IC

[Morocotopo]

Hi guys!
I´m starting to design a PCB for the DC2 Dimension C. I made the Topopiccione one (hope that´s the right spelling...) some time ago, it´s nice ´n all, but wayyy too big! Now I want one that fits in my pedalboard without kicking other pedals out. The size target is a BB box used "sideways". Also, I want to retain the original´s mono to stereo jack switching, so I won´t make it true bypass, but a full clone of the original.
Looking at the schem, I hit the first snag: the original uses a BA634 IC. That´s a single T-type flip-flop. It´s absolutely impossible to find, not even a datasheet is available. So, it has to be replaced. This is the original switching part of the schem:



And searching for alternatives, I think the closest thing would be the typical Boss bypass:



But, but...

The Boss one is, I think, a D-type flip flop, and I need a T-type one... so, the question is: What should I change in the Boss type one to make it work as the DC2 one? I´m a little confused about flip flop types: D-type, T-type, JK-type... Or, is there another functionally similar circuit other than the Boss one? I believe you can make flip flops from gates, but I discarded that because of the chip´s size... I need to save as much space as I can.
So, all of you Flip-Flop experts, what do you think? Any other suggestion as to how to implement the needed switching is also welcome.

Hope i made myself clear. Thanks for reading.

[R.G.]

Looking at the schem, I hit the first snag: the original uses a BA634 IC. That´s a single T-type flip-flop. It´s absolutely impossible to find, not even a datasheet is available. So, it has to be replaced...

The Boss one is, I think, a D-type flip flop, and I need a T-type one... so, the question is: What should I change in the Boss type one to make it work as the DC2 one? I´m a little confused about flip flop types: D-type, T-type, JK-type... Or, is there another functionally similar circuit other than the Boss one? I believe you can make flip flops from gates, but I discarded that because of the chip´s size... I need to save as much space as I can.

D flipflop: output Q goes to the same state as the "D for data" input when the clock is activated.
T flipflop: No input except the clock; toggles ("T") when the clock is activated.
JK flipflop: has two inputs (J and K) as well as clock; does an assortment of things when the clock is activated, including acting like a D or T, or a couple of others.

The BA634 is a T. The Boss is a T as well. You can make a T flop out of a D flop by tying the D input to the -Q (that is, inverted output) pin.

My suggestion? Use a CD4013 dual D-flop. This is twice what you want, but it works well with 9V.

There are some single flop packages in Fairchild's "Tinylogic" line, but they're generally 5V only and SMD.

[Morocotopo]

Thanks R.G. So, if the Boss is a T also, ermmm, in the schem, just leaving out one of the FETs and using the other "control line" for turning on or off the FETs in the DC2 would work? I´ll make a schem later to see if I´m on the right track.
I´ll also investigate the 4013 road.

[R.G.]

if the Boss is a T also, 

Yes. The wire from the footswitch is a specially constructed "clock" signal. Get a clock, flip state. Toggle flipflop.

ermmm, in the schem, just leaving out one of the FETs and using the other "control line" for turning on or off the FETs in the DC2 would work?

Conceptually yes. In practice... "would work" is kind of rigid. The objective is to switch the JFET gates in the original, plus work the LED. There are differences. The Boss circuit uses a footswitch to ground, OK. But it's a 1M pullup, not 47K. If you built the Boss flipflop, you'd have to change that to 1M. On the output side, the Boss circuit pulls the LED to ground to turn it on; the BA circuit pulls it up to some high level. You could preserve the Boss style of LED by leaving the LED where it is on the Boss FF and putting the output to the JFETs on the opposite side. Now when the JFET gates are pulled high as in the original, the LED is pulled low and comes on. It does the same action as the BA IC, but uses opposite polarity on the LED The Boss circuit may well not operate at all if you try to use it to pull an LED high; it's got limited pullup ability. But using the other/complementary output works almost as well. Just not exactly the same as the original.

I´ll make a schem later to see if I´m on the right track.  I´ll also investigate the 4013 road.

Good plan.

[Morocotopo]

OK, let´s see if I got this right...



How about it? Later in the day I´ll try to breadboard it to see if it works in practice. I´d rather use this than a 4013 flip flop, because it´s easier to "distribute" on the PCB than a chip, and I´m trying to make the smallest PCB possible, and this allows to fit parts here and there in little spots that would otherwise be left unocuppied, in other words, to maximize PCB space use.

[R.G.]

That's a good starting place.

[Morocotopo]

GODDAMIT!!!

I just spent three or four hours trying to make this damned flip-flop work on the breadboard! I felt like a total beginner! Me, the super electronics guy, already built two tube amps, countless stompboxes, even designed (ahem, cough, cough) a few ones meself!

Of course, it was operator error. Sigh. Amazing how two transistors and a few resistors and caps can make fun of you (yes, I heard them laughing very faintly).

But, it works (No kidding! Countless Boss boxes are testament to that  )!

I mean, it works for my intended use. Drives three FETs nicely. I used 2N3904 transistors and instead of a 3K9 R for the led, a 1k to get a bit more brightness. 2SK30A GR FETs.
I have one question: The Zener, is there as a lo batt indicator? So that when the batt reaches 5V6 plus the LED drop, plus the R drop, the LEd won´t turn on?

Thanks R.G. for the guidance.

[Earthscum]

GODDAMIT!!!

I just spent three or four hours trying to make this damned flip-flop work on the breadboard! I felt like a total beginner! Me, the super electronics guy, already built two tube amps, countless stompboxes, even designed (ahem, cough, cough) a few ones meself!

Of course, it was operator error. Sigh. Amazing how two transistors and a few resistors and caps can make fun of you (yes, I heard them laughing very faintly).

But, it works (No kidding! Countless Boss boxes are testament to that  )!

I mean, it works for my intended use. Drives three FETs nicely. I used 2N3904 transistors and instead of a 3K9 R for the led, a 1k to get a bit more brightness. 2SK30A GR FETs.
I have one question: The Zener, is there as a lo batt indicator? So that when the batt reaches 5V6 plus the LED drop, plus the R drop, the LEd won´t turn on?

Thanks R.G. for the guidance.

Ha! I know what you mean... I've heard their little silicon-muffled insults, as well!   Nobody believes me...

Look at what DOD uses for their LED's. Basically, on power off, the LED is shunted by a transistor. If the voltage drops below about 6V or so, the LED gets noticeably dimmer, and fast. When I was playing with my FX-91, I noticed that it's only about 1/4-1/2 volt between noticeable to not turning on at all. (was thinking BOSS, *derp*... my DOD does what I describe, but not sure how, but doesn't like anything under about 6V, which probably turns into less with the circuit loading)

[R.G.]

Of course, it was operator error. Sigh. Amazing how two transistors and a few resistors and caps can make fun of you (yes, I heard them laughing very faintly).
But, it works (No kidding! Countless Boss boxes are testament to that  )!

That's always how it feels when you unravel the mystery. We've all been there.

I have one question: The Zener, is there as a lo batt indicator? So that when the batt reaches 5V6 plus the LED drop, plus the R drop, the LEd won´t turn on?

That's what I think it does.