Crash Sync on vero: No sound...

[Coriolis]

Has anyone built RLBJR65's vero layout of the Crash Sync with succes?
I have been debugging for a few days now, and not quite gotten it to work.

What I got:

- sound on the output, but it is strictly the 555 I'm hearing. That seems to work fine though. I subbed the 47n cap on pin 2 of the 555 for a 100n, cause that's what I had. Don't know if that might affect the ability of the oscillator to sync to the guitar signal. As it is now, the 555 is on all the time.

- no sound from the opamp. I'm using a tl072, and have been tracing the signal with an audioprobe. It stops at pin 2 (inverting input) and there's noting after that.

TL072 voltages:

Pins

1  7.15
2  5.93
3  7.15
4  6.40
5  5.86
6  5.89
7  6.89
8  7.72

These are with no signal and nothing connected, except for a 9 volt batt.
Can anyone tell me if these look right, and if not, what they should be?
As far as I can see, the layout checks out with the original Hollis schem,
but I'll go over it again.

Thanks

C




RLBJR65

[Connoisseur of Distortion]

well, pin 4 should be at 0... as it is the ground... and i *think* that the other pins (with exception to 8, which is powered) are a little high... someone correct me if i'm wrong

[guitarhacknoise]

well, I went to measure V's on mine, and found out that I am in the same boat, funny how stuff just stops working.
so maybe we'll get this done together.
BUT, there are a few differences to take in......
I am using tlo82
I am using a 12v supply
I have 0v @ ground/pin 4
I used the layout provided on mr. hollis' site to draw and etch the board.
anyways I will get this probing started.

[guitarhacknoise]

alright, check it.........
With the probe I had signal all thru the audio path till I hit the 555.
this is the third 555 I've fried!
I replaced it.
I brought the P.S. down to 8.48v
so here are the pin v's for both IC's

TLO82:
1) 4.18v
2) 4.19v
3) 3.88v
4) 0v
5) 4.11v
6) 4.37v
7) 1.17v
8.48v

CMOS 555, these measurements are at "idle", as in......no input signal .......the 555 is not being triggered to "do the do"
1) .1mv
2) 14mv
3) .9mv
4) 212mv
5) 5.64v
6) 14.1mv
7) 14.1mv
8.48v

does this circuit eat 555's like crazy? or am I rockin 'em to death
but seriously I did make a few component changes from Mr. Hollis' suggested values.
Which Might do it, as far as the rockin' it to death thing.
the 150k input resister Was dropped to 27k (alot easier to clear the gating with out a preamp)
the 1meg betwixt pins 5 & 7 was dropped to 470k (actually can't remember why I did this, but I did it so.......)

-matthias

[RLBJR65]

Coriolis, I agree with Connoisseur of Distortion, those voltages look all wrong. I would expect to see opamp voltages similar to those guitarhacknoise posted.

Make sure you don't have a bridge between strip 8 and 9, or pin 4 connected to 8 instead of 9 there would be partial battery voltage on 8, not sure it would be as high as you posted for pin 4 but close.

[Coriolis]

Right, back on the job!
GuitarHackNoise has made me a little worried that I'm burning 555's, since I have no sound either, after fixing a couple things.
I found that I had forgot the jumper that goes from pin 4 on the TL072 to ground. That gave me these voltages, from a battery that isn't fresh, and with a guitar and amp connected:


TL072 - Pins
1:  +7.00
2:  +1.86
3:  +6.99
4:    0.00
5:  +3.63
6:  +3.70
7:  +1.33
8:  +7.57

555 - Pins
1:    0.00
2:  +0.04
3:    0.00
4:  +0.33
5:  +5.04
6:  +0.04
7:  +0.02
8:  +7.56

As I said, this is with the effect plugged in, but with no signal from the guitar (no playing).

Those 555 readings aren't as high as those GuitarHackNoise posted, and I believe you lowered your supply voltage to 8.48?

After going over it with the audioprobe, I still have no signal after  pin 2 (inverting input), nothing coming out of pin 1.

Something puzzles me about the vero layout:
The 10M resistor going from input to ground on the original schematic doesn't go straight to ground on the layout, instead it basically goes to one of the 56k resistors (think it's one of the two that form a voltage divider on the schem). I'll have to go over this again...

[guitarhacknoise]

:shock:
You done did it!
I took a look at RLBJR65's vero layout, And although I am the worst at processing vero layouts.............I See what you are saying About that 10M.
Unfortunately, I found a few other problems,
The inverting and non-inverting inputs are switched, I don't believe this to be wrong so much as confusing.
RLBJ has a 1 k going from pin three to the positive end of the 10uF , I think that should go from pin three to the second strip from the bottom, and then I relize that the two 10uF are supposed to connect together at their pos. ends.
there maybe more, I am easily turned around with these things
we need a better eye to verify, I'll continue to look.

-matthias

Has any one built this layout?

[Coriolis]

I actually had problems seeing which inputs were being used on the Opamp (on the original schem), cause I don't know exactly what to look for, but comparing RLBJR65's layout with the pcb-layout from Hollis' site, I beginning to see a lot of differences! For instance, you are right about those two 10uF's.

I no hawkeye either, when it comes to deciphering layouts, so it would be good to have someone else chime in with their findings, build reports,etc.

Didn't you build it with the layout from Hollis' site?

[guitarhacknoise]

yeah, I made a hand drawn PCB Following Kent Stevenson's board off of the Hollis Site.
but I'm still burning up the 555.
$2.00 at the shack, I need to order a bunch of the 7555's
but.....................lazy.
As far as what inputs are what on a schematic,
for this circuit, you need to know what pins are represented by what part of the op-amp sections. this uses a standard pin-out ,dual op-amp.
check out a data sheet for pin-out.
But,within the triangle,
the + denotes the non-inverting in,
the - is inverting
(I think thats right)
the other is out.  
as always, double check what I think!
I would like to know about the effect, if any, of the inputs being switched on the first op-amp,
with the inputs not switched on op-amp #2
-matthias

[Coriolis]

GuitarHackNoise:
I guess I don't really understand that opamp circuit... :?
It would seem to me, that the job of the voltage divider consisting of two 56k resistors, that can be seen in the bottom left corner of the schem, is to provide 4.5V to some part of the circuit, most likely the opamp, right?
The reason I'm asking is, I can see a lot of the voltages you posted on the opamp are below 4.5...

Oh, wait! Pin 4 is ground and should be 0V, while pin 8 is vcc+ and should be
...? Around 9V, or around 4.5V? I'll have to check it...

Ok, got it: Pin 8 should be whatever the psu delivers, no reduction in voltage there. Not according to the vero layout, or the pcb. And I guess since the schem doesn't show any special circuitry with regards to pin 8, I've got that part right.

Still don't know what that voltage divider does though.  Looks like it supplies the inverting input on one half of the TL072, and the non-inverting input on the other half. I need some basic understanding of opamp circuitry I guess  :wink:

[Coriolis]

Oh, you got there first!  
I've already got the datasheet for the TL072 I'm using, so thats sorted.
Still don't quite know what I'm doing tho... :roll:

[Coriolis]

Moosapotamus (in case you are reading), you built this effect, what layout did you use? And did you have any problems? Anybody else?

[jmusser]

I built this circuit straight to perf board off the John Hollis schematic, and never had a speck of problem with it. I used the Cmos timer and TL082 from Radio Shack. The only thing I haven't done yet, is get the timer pot run through an expression pedal. I guess I just got lucky.

[Coriolis]

I think I'm going to try etching one from the Stevenson layout, even if I'm a bit worried from what GuitarHackNoise tells me of it...

[guitarhacknoise]

It appears to me that the Voltage Divider you are talking about, is feeding almost all the pins of the op-amps. I don't know this much to even think that may be correct but it is very confusing.
as far as my prob goes, I think I'll switch that 470k I subbed for the 1M it calls for.
seeing as I cannot remember why I did it in the first place, and it is hitting pin 4 of the 555, which is the reset. Ill measure first, then replace it.
-matthias
I did the switch, the voltages only changed slightly. it seems to have affected the sweep range, but the sound remains the same.

[Coriolis]

Hmm...I don't see any 1meg's going to pin 4 of the 555? Not in the schem or the pcb?  :?:  :?:

[guitarhacknoise]

Sure you do...........I just did'nt explain fully.
pin 5 of the tlo72, there is a 1M going to pin 7 of said tlo72, it then goes thru the 10k to the voltage divider you talked about  and on down the line till it ends up at pin 4 of the 555.
not sure how this is all related, but it was something I had messed with so I figured it could be the culprit.
I'm just a color by numbers guy so................
-matthias

[Coriolis]

Well, I guess you're right in saying that pin 4 of the 555 is seeing a 10k and then a 1meg... :wink:

[guitarhacknoise]

you know, I don't have a clue as to how/why this thing works.
Pin 7 is an out, while pin 5 is an+ in. so I guess the 1M is in the feedback loop of op-amp #2,
and the 10k comes off the output of that op-amp, then over to pin 4 of the 555, triggering the reset.
is this correct?
-matthias

[Coriolis]

That would be my theory, but I suspect I know even less than you  :oops: