Heliotrope Help

[canman]

Hi guys,

I'm working on a Heliotrope build, and I can't get any signal out of it.  I'm using this layout:



This layout has been verified, so I know I went wrong somewhere.  I used a TL071 instead of an LM741.

And here is a schematic that I assume was used to create the layout:



These are the voltages that are supposedly correct:

ic1
1. 4,53
2. 4,52
3. 2,26
4. 0
5. 4,5
6. 4,5
7. 4,5
8. 9,0

ic2
1. 0
2. 7.68
3. 5.68
4. 0
5. 0
6. 5,96
7. 9,18
8. 0

q1
d 4,5
s 4,5
g 1,85

I'm getting voltages that are very similar to these voltages...a couple of the pins are reading maybe 1v lower than these, but I figured that's probably OK.  Where I'm having issues is ic2 (TL071) pin 6.  I'm getting about 0.7v, while the list above says I should be getting around 5v. 

Can you guys help me out here?  I assume R1,3, or 4 would be the culprit, but oddly enough, I just noticed that there are no values on that schematic, so I'll keep looking for a different schematic, but until then...any help would be very much appreciated.  Thanks!

[canman]

Sorry to post in this thread again so soon after posting it, but I've been studying the schematic a bit more, specifically R4 and R1...are they creating a voltage divide?  Is that why I need roughly 5v at pin 6 of LM741 (TL071, in my case)? 

[duck_arse]

redraw that circuit, it's doing my head in. it has a dual opamp jambed in a single opamp symbol.

(on that awful circuit diagram) R14//C3 form a supply filter to prevent supply noise. R4//R7 form a voltage divider (?Vref?) between clean supply and ground, with C1 smoothing. R3 feeds Vref to the non-invert pin 741 to set its bias point. erm, and I take it that stage is an oscillator driving the fet on and off, yes?

the pin 6 should be very close to the voltage at R4//R7 (what do you measure here?).

[canman]

I get approximately 1.5v at pin 6 of the TL071 (not .7v like my initial post).  Will it make a difference if I used an LM741 instead?

I didn't design this circuit, so to answer the oscillation question...shoots, I don't know, haha.

[Hatredman]

MY EYES!
THE GOGGLES DO NOTHING!

[canman]

Sorry, I didn't realize that schematic was crap...

I got an updated schematic, but it was posted on another forum, and I'm not sure if the rules permit me to post the schematic here..?  Can I post it?

[duck_arse]

as far as I'm concerned, yes, post it. (I'm not the boss, though, but I think hatred will appreciate, what with the goggles and all .....)

by my estimations, trying to read the vero, the Vref divider is 10k//10k. being even value, Vref should be V+/2.  you can work out what that voltage should be ..... there will/may be some loading by your meter AT the IC pin, but if the pin6 is very near the Vref value, all is good there. there will be minimal difference between the 741 and the 071.

is this a tremolo or something similar?

[canman]

It's not a tremolo, it's pretty close to a ring modulator...a crazy noise box that just sounds interesting to me  

Here is the traced schematic:



What I find interesting is that I get about 4.5v at the socket of pin 6, when the TL071 isn't in place.  But when I put it in place, I get a much lower voltage reading.  Is that normal?

I also built this one up again using Sabro's layout, and I'm having the same results:

[nocentelli]

Just to note, the 3k3 feedback resistor in the oscillator (R6 in the newer schematic, R11 on sabro's vero) is supposed to be 22k. It won't prevent the effect working at 3k3, but it does make the effect more pronounced at 22k.

[WhiskeyMadeMeDoIt]

Just took a trip to YouTube land and had a listen to the heliotrope.  Interesting sound but I had a thought when he swept the frequency while playing.  What if the frequency pot was switched out for an LDR and it was modulated with another oscillator?  May have to breadboard that up and test it out. 

[nocentelli]

Envelope modulated frequency might be fun, too.

[WhiskeyMadeMeDoIt]

Yes yes yes ! Should be able to squeeze both ideas into a box with a selector for envelope or oscillator. 

[canman]

Well...you guys have fun with this circuit, haha...it's been giving me a headache for some time now, I'm gonna put this one in the drawer and try to get it working again on a rainy day or something.

I may give the one chip chorus a go, seems like fewer things could go wrong, and the pt2399 locking issues have been mostly solved...thanks for the help everyone!

[WhiskeyMadeMeDoIt]

Canman don't give up on it just yet let it sit a few days and go back to it. check all your traces for shorts or bridges. they can be very small. If I have some time in the next few weeks i'll breadboard this using the schematic you posted and see if it works. On a weird and related note I was looking through some circuits for envelope followers and somehow by following links from one post to the other ended up on the One Chip Chorus post. I read for a bit and decided to get back to what I was doing. Now here you are saying you are going to build it....  Strange coincidence. Sorry for the derail on your post.

[nocentelli]

Schematic definitely works, the only reason this hasn't left my breadboard and been boxed is the incessant carrier bleed whine.

[duck_arse]

What I find interesting is that I get about 4.5v at the socket of pin 6, when the TL071 isn't in place.  But when I put it in place, I get a much lower voltage reading.  Is that normal?

pin 6 connects to 4V5 via the (?)3k3 and 47k, so it should be around Vref w/ no IC fitted, as should pin 3. can you give us your voltages again, with respect to your new circuit diagram?

[duck_arse]

I hadda poke at the oscillator section on my brand new breadbord tonight. it's a weird thing.

without the IC, the voltages at R16//R17 and pin 3, 6 and 2 should all be about V+/2, my pin 2 measured down to 4V29. with the IC, it's a different matter, with AC at pins 2, 3 and 6. I set to lowest speed, low range, P2 to middle, and still got about V/2 reading on dc range, with the meter pulling the pin2 reading way down, shifting the osc freq. on the cro, I had 6V p-p sq wave at pin 3, 7V p-p at pin 6. (this with the 3k3 feedbacker.)

tl071 or lm741, made no diff I could see.

[canman]

Bah...screw it, I can't get it.  I guess everyone has a circuit that they just can't seem to get...looks like this one is mine!  Built it twice, same problem both times...clearly the problem is the builder.  I'll try again in a month or so when I'm bored and need something frustrating to do!

[rousejeremy]

Post good pics of the top of the board, the underside and your offboard wiring to the pots and switch.