Help with 4049 oscillator (Anderton tremolo)

[jez79]

Hey folks,

There's so much I'd like to discuss with you folks! I've been dedicating a large amount of time energy and $$ to the electronics hobby and have been making/selling pedals to many friends (I've played bass with MANY musicians over the years, making facebook useful for moving builds and getting commissions!)
I've been very lucky (or is it skill??) with builds so far, many working with no troubleshooting. Last few troubleshoots were good finds: missing GND connection, one wire in wrong spot, etc.
However, the Anderton tremolo i've been trying to get working smoothly seems to be presenting a design troubleshoot instead of a mechanical troubleshoot. I've been ballsy and haven't bothered breadboarding new circuits. Stuff on here, GGG and other good sites seem fairly tried and tested so I just solder a circuit right off. I know I know.. I'd save myself some trouble and give me a shot at optimizing to my tastes, but up to now I've been focused on getting units made.

HELP: http://www.generalguitargadgets.com/pdf/ggg_catrem_sc.pdf
Maybe it's my 4049 chip; schematic asks for 4049U, but the U is absent from my chips, bought in the 90s. 4049PB I think. I had checked the datasheets and they're both inverters, but maybe there are other differences (buffers, etc).
I can get the oscillation to work, and make the tremolo function (homemade LED/LDR). Sounds fine, but the oscillator is all kinds of messed up!

With the chip voltage (and unused inverter tie-down inputs) biased with the suggested 1k, I get the voltages GGG suggests, 5.4V or so. All up to spec.
BUT: pin 6 (labeled square in schematic) gives me a smooth triangle wave, and pin 2 (labeled triangle) gives me a choppy square.
The pin 2 output does not give full range of oscillation rate. The signal drops out at about 5k/50k pot, and it seems but a fraction of the oscillation rate of the pin 6 output.

I breadboarded the oscillator with another 4049, very quick and easy. Gave the same results, so I played around with values and upped the power bias resistor. Upping a few k to 2k2 or even 4k7 helped pin 2 output some, but it was still a fraction of pin 6's rate. Upping it too much make the smooth triangle wave behave strangely and hiccup at the top of it's swing. These results were at around 3.5V.

I put things away, and tried to accept the wait for new 4049 chips, hopefully compatible with this circuit (4049U types).
Next day, I decided to fire up the breadboard circuit for fun, and lo and behold, I'm getting perfect behaviour across the whole speed range for both pin outputs! (the output shapes are reversed from what the schematic says though... I checked and rechecked my connections to make sure cause that's a disfunctional discrepancy) What happened!? I checked the bias voltage and it was 2.88V. I was getting this with a 1k5 resistor, much lower than that same resistor the day before (around 4V). Not sure what changed, perhaps discharging something while checking with multimeter?

I tried changing the bias resistor in my soldered circuit, but it did not help. I put a 10k trimpot in there, hoping to find a setting that would give me 2.88V and get the thing oscillating properly. Nothing got me to proper behavior or 2.88V. Breadboard oscillator is there, blinking, mocking me for not building it first.

I played around with the breadboard circuit's bias resistor again, and now I cannot get that perfect behaviour nor 2.88V. The voltages on pin 1/9/11/14 also oscillate now (they may have before too, but not at 2.88V, it was rock solid), 3.29-3.40 or so, at a fixed rate, independant of oscillator rate...

So, any advice on this oscillator? Could my non-U 4049 have anything to do with it? The waveshape difference is very weird, as is their different response to changes in the speed knob resistance.
Thanks! Cheers!

[anotherjim]

The "U" is everything. A U chip (or often UB) is un-buffered. Each inverter is a single MOS complementary pair. The Non-U is a B for buffered version. Each of their inverters consist of 3 pairs in series.
Only the U or UB devices will behave in a linear fashion. The buffered ones will be doing their best to make everything digital.

[duck_arse]

if you are desperate, and have a 4007 handy, use that instead (after the necessary hacks/translations). they only come as unbuffered.

or, use a 4069, also only unbuffered (different pinout too).

[PRR]

On that plan, pin 6 is the Integrator output, we would expect a triangle. It appears the drawing you link is incorrect.

Original-recipe '4049 were single-stage. As Silicon costs dropped, many '4049 designs threw-in more stages (buffering) for better performance in logic circuits. Apparently you have to "ask" for Unbuffered now, if you need early-chip action. I can't guess what you got in the 1990s, as I did not notice the change at the time.

[jez79]

Thanks for the replies folks!
I'll have to shelf this project for a few weeks till 4049U get here.
I had a few digital logic chips from uni days (4049BP, flipflops, etc), think I bought a few extra when making a counting switching circuit for a friend's art project.
I'll post an update about this oscillator here when they come in.
I'm hoping the square wave will give a very choppy tremolo effect, though LED/LDR is probably poor at translating a sharp LFO signal change.
I got a successful Kay trem going, but it's not choppy enough... I'll try tweaking depth parameters and see if it can go further.
Also made an EA trem, but that one is very good at smooth LFO
Suggestions for a trem circuit that will get VERY choppy?? Something I can try in the meantime, perhaps even breadboarding this time??
Thanks! Cheers!

[garcho]

though LED/LDR is probably poor at translating a sharp LFO signal change.

they still sound like they have corners.

try a CV tremolo, like something with an LM13700. then you don't have to worry about the LED/LDR slew rate. or ye olde 555.

tiny tremolo (555)

R.G. & OTA VCAs (LM13700)

[duck_arse]

there is some helicoptering mentioned in this thread (and it took me twenty minutes to find; searched for "whump")

http://www.diystompboxes.com/smfforum/index.php?topic=112197.0

[jez79]

Thanks folks for the vote of confidence in the 4049U chips.
The unbuffered units worked perfectly with 1k on power.
It's still not quite choppy enough. I will try the other circuits mentioned above.
I'm looking to get a stutter effect