Leyland Pedals Ultra Simple Tremolo layout and some questions...

[moid]

Here's the voltage for the chip (currently a TL082)

Pin 1  8.2V
Pin 2  2.1V
Pin 3  8.1V
Pin 4  0.01mV
Pin 5  8.1V
Pin 6  1.6V
Pin 7  8.1V
Pin 8   8.81V

Does any of that look weird? To me it seems odd that 6 and 7 (which are currently tied together are completely different values... I'm not using either of those pins, but that looks odd to me. I wonder if this breadboard is wrecked and that's why things aren't working?

[antonis]

You probably tied toghether and to Vref unused pins wrongly..

pin 5 to Vref (pin 3 or any convenient point)  and pins 6 & 7 shorted..

P.S.
"Something" messed up the whole bias configuration..
Pin 3 (and 5 after shorting) should measure half-supply voltage..
Your op-amp is heavily saturated..

[moid]

Hello everyone
Sorry about the delay in replying, I had to go back to work this week... so progress has been slow. For extra fun we are having a heatwave - it is 31C today, I am not sure if I should melt or evaporate. So of course it seems like perfect time to sweat over hot breadboard! I decided to completely rebuild the circuit from scratch... and it still doesn't work. It behaves identically to how it did before, with the only change being when I add Antonis' shorts to the circuit the audio is slightly distorted - not louder, just clipping. I measured the TL072 chip voltages and did without the shorts and with the shorts:

No shorts
Pin1.  4.9V
Pin2.  1.49V
Pin3.  5.6V
Pin4.  0.8mV
Pin5.  1.04V
Pin6.  1.067V
Pin7.  1.41V
Pin8.  8.8V

With Antonis' shorts
Pin1.  5.1V
Pin2.  1.49V
Pin3.  5.6V
Pin4.  0.3mV
Pin5.  5.6V
Pin6.  5.6V
Pin7.  5.6V
Pin8.  8.8V

Antonis - I think that shows the voltages you were expecting with your shorts added? So presumably the fault is somewhere else in the circuit? Any idea where I should look or what to look for? Hope you are all somewhere cooler!

[Eb7+9]

I just tried a TL082 chip in place of the TL072 (they seem to have the same pinout) but no joy there

let's back track a bit ...

first of all, don't short op-amps together like Antonis stated
that's complete non-sense

the oscillator isn't oscillating obviously
just focus on getting the oscillator going

I'm assuming you don't have a scope
and measuring DC voltage on an astable circuit that's supposed to oscillate is again complete non-sense

what you should do is stick an LED and 10k resistor between pin-1 (output) of op-amp and gnd
THIS will tell you if you oscillator is doing anything // what it's supposed to ...

ie., square wave = on // off // on // off

ignore the rest for now ...

it's the same oscillator circuit as what you have in your box
if you made it work once you should get it to work twice

exactly the same way ...

[antonis]

first of all, don't short op-amps together like Antonis stated
that's complete non-sense

Antonis just proposed the dedicated wiring for not used op-amps..
(non-inverting input at Vref and inverting input & output shorted..)



If that is non-sense, put the blame on various op-amp manufacturers..
(my 2 cents..)

[PRR]

....I am not sure if I should melt or evaporate....

No choice here. It is 100% relative humidity now. The afternoon may get as dry as 95%RH. Then the rain starts. We'll have NO evaporation for a while. (The grass clippings I mowed 2 days ago are still fresh and green.)

In the western desert, Las Vegas is 16% RH but 102 degrees F (39C) at dusk, so melting is mandatory.

[Eb7+9]

I thought Antonis was recommending doubling on everything -my bad

must be a simple issue like input swaps

[moid]

No choice here. It is 100% relative humidity now. The afternoon may get as dry as 95%RH. Then the rain starts. We'll have NO evaporation for a while. (The grass clippings I mowed 2 days ago are still fresh and green.)

In the western desert, Las Vegas is 16% RH but 102 degrees F (39C) at dusk, so melting is mandatory.

Yikes, I will stop complaining! Thankfully it rained a bit today so we have a mild 24C now, but much humid, hopefully tomorrow will be cooler still. At least it meant I could focus on this circuit a bit.

Eb7+9 - sadly I don't have a scope, but thanks for your cool probe suggestion! I have kept Antonis' shorts in and made a little LED and 10k probe and started sticking it into the circuit - I think the issue is between a 10uF capacitor and the 33k resistor - the LED turns off if I touch the ground leg of the cap or the 33k resistor leg that connects to the cap. I tried substituting the capacitor for another of the same value and got the same result - it seems to me that the capacitor is stopping the flow of electricity. That said, there is no evidence of a pulse anywhere in the circuit - the LED is either on or not. I have tried this with the Speed pot at minimum and maximum sweep, the only difference is the LED is less bright when the speed pot is at CCW.

Pin1 light on
Pin2 light off
Pin3 light on but dim
Pin4 light off
Pin5 - 8 light on

The LED is on from pin1 to the speed pot, it works up to the long leg of the 10uf cap at the top of the schematic, but nothing gets past that leg. The other 10uF cap is fine on its long leg, with no light on the stripe side of the cap. Does any of this make any sense?

[antonis]

it seems to me that the capacitor is stopping the flow of electricity.

Partially true..

Could we have a final schematic, plz..??
(not something like the one with permanently grounded Base of BJT..)

[moid]

Yes, I realise now I said that about the capacitor that the statement is a bit obvious... however I'm pretty sure that the cap should discharge some electricty every now and then (maybe a few times a second) so that the circuit can work! I don't think it is doing anything.

Here is an uptodate schematic. The guilty capacitor is labelled at the top of the schematic. I have tried swapping it for other 10uF caps but there is no difference.




By the way, sorry for the slow updates, work has started up again and I've not had much time to look at this circuit (and I was able to build and finish a totally different circuit on the side - the Memory Loss-a-like, based on the Seppuku FX pedal of the same name and it's great fun to play with). Back on this one now, not getting distracted by anything else... oh hello park autowah, well how have you been?

Thanks for the help!

[Eb7+9]

Thanks for your update ...

personally I don't think wiring up the second op amp is necessary or even a great idea ... I would try working with one side only and let the other side clamp to either rail - it's generally no biggie ...

wondering if your 10uF caps might be exceptionally leaky ??
try turning them around

have you got any film caps in that range ?!

also, the 20nF cap is the one that really gets the ball rolling so to speak
try a 100nF film instead if you have one

[moid]

Thanks for replying so quickly!

I tried some of your suggestions - swapped the 22nF with a 100nF - made no change, the LED probe does not light up after the ground leg of the 10uF capacitor.

I removed the shorts (pins 6-7 and pins 3-5). no change, I've left them off for now.

I tried a different brand of 10uF capacitor (same result).

I then swapped the 10uF around so that the stripe/ground faces towards the IC part of the circuit and the LED probe lights up on the other leg - so electricty is now going through the cap. The LED stay lit brightly until it hits the 33K resistor. After the resistor, the LED is still on but noticeably dimmer. The LED light probe lights up to Lug 1 of the depth pot as long as the pot is fully CW. If I put the LED probe on Lug 2 or 3 the LED turns off. on Lug1 if I turn the pot back to CCW, the LED dims and turns off and no setting will allow anything to happen to Lug2 which is weird; I would expect some voltage to appear there and light up the LED? Is the Pot too strong, maybe I should try a smaller pot? OK just tried a 1K pot and there was no effect, except that when sweeping the pot, there was a gentle slow fading of the audio from off (full CCW) to on (full CW). With the 10K pot the audio is off until near full CW when it suddenly turns on. No tremolo of course. When I put the LED probe on lug 1 of the 1K pot the LD remains off which is odd. With the 1K pot in place the LED does not light up if I touch the 33K resistor on the side facing the pot. If I put the 10K pot back I do get a lit LED at that point. Electricity is bloody weird!

Should I try a bigger pot?

I don't have any film caps of 10uF size (I didn't realise you could get such a thing; I thought they stopped at 1uF and everything was electrolytic on any number higher than that?). I have found them online - they are really expensive - I will order some if you think that is the solution.

[PRR]

> film caps of 10uF size (I didn't realise you could get such a thing; I thought they stopped at 1uF and everything was electrolytic on any number higher than that?)

You can get film "any" value you want to pay for. If you build an atom bomb you may want very large low-loss caps. That's how one ban-busting bomb project was uncovered, the cap supplier thought the order was funny.

10uFd is actually a reasonable value if you actually "needed" film. (You don't).

Panasonic ECQ-E1106KFB
10uFd
Voltage Rating - DC  100V
Polyester, Metallized
Size / Dimension  1.024" L x 0.453" W (26.00mm x 11.50mm)
Height - Seated (Max)  1.024" (26.00mm)
$3.27 at Digikey

Or for "more!", try MMP0100F33
(1,100uFd 600V)
CAP FILM 1151.3UF 480VAC RADIAL
Cornell Dubilier Electronics (CDE)  1 : $1,060.50

For pedals you could use a 16V e-cap costs like $0.33 each and smaller than a pencil eraser.

[Eb7+9]

Thanks for replying so quickly!

I tried some of your suggestions - swapped the 22nF with a 100nF - made no change, the LED probe does not light up after the ground leg of the 10uF capacitor.

I removed the shorts (pins 6-7 and pins 3-5). no change, I've left them off for now.

I tried a different brand of 10uF capacitor (same result).

I then swapped the 10uF around so that the stripe/ground faces towards the IC part of the circuit and the LED probe lights up on the other leg - so electricty is now going through the cap. The LED stay lit brightly until it hits the 33K resistor. After the resistor, the LED is still on but noticeably dimmer. The LED light probe lights up to Lug 1 of the depth pot as long as the pot is fully CW. If I put the LED probe on Lug 2 or 3 the LED turns off. on Lug1 if I turn the pot back to CCW, the LED dims and turns off and no setting will allow anything to happen to Lug2 which is weird; I would expect some voltage to appear there and light up the LED? Is the Pot too strong, maybe I should try a smaller pot? OK just tried a 1K pot and there was no effect, except that when sweeping the pot, there was a gentle slow fading of the audio from off (full CCW) to on (full CW). With the 10K pot the audio is off until near full CW when it suddenly turns on. No tremolo of course. When I put the LED probe on lug 1 of the 1K pot the LD remains off which is odd. With the 1K pot in place the LED does not light up if I touch the 33K resistor on the side facing the pot. If I put the 10K pot back I do get a lit LED at that point. Electricity is bloody weird!

Should I try a bigger pot?

I don't have any film caps of 10uF size (I didn't realise you could get such a thing; I thought they stopped at 1uF and everything was electrolytic on any number higher than that?). I have found them online - they are really expensive - I will order some if you think that is the solution.

sorry, I typed without thinking carefully ... I meant any better caps, like BP electros ...
but the circuit shouldn't be that finicky anyway

strange - like, you've already made this LFO work before right ?

yes, electricity can seem weird ...

btw, the 10k+LED "probe" is only meant to go between op-amp output and ground
making sure to orient LED properly (try swapping it around)


are you by chance tying pins 1 and 8 together ? ... you know, the way the schem is drawn almost looks like it
only thing else I can suggest is measuring those 220k resistors

otherwise, who knows ...

ok, that's enough torture - thx for trying this little idea out

[amptramp]

Leyland pedals?  As in British Leyland cars, famous for using Lucas Prince of Darkness electricals?  No wonder trying to make it work is a six-page thread already.

[antonis]

famous for using Lucas Prince of Darkness electricals?

Pure nightmare..!!!

[PRR]

....a six-page thread already.

Six? I see three. AH! There is an option. Profile, Modify Profile, scroll, Messages per page: Default is 20 but a single side-drift can go that far and still return to topic! 50 means more to track but all on one page.