FV-1 Multi effect full forum project ready to go. (ShimmerVerb Also)

[Ice-9]

OK.. having now measured the regulator  it doesn't seem to be the problem, as I'm getting 6.68 on one side (closest to jacks.. the regulator input, yeah?) and 3.11 on the pin closest to the top.. I also tried swapping it out for a new one.. still getting distortion with the hot-pickups. I can't really notice it with my other Tele..

Ok, now something doesn't sound correct there, the 3.3v reg should of course give out 3.3v but on the input to it you should be reading 9v or there abouts not the 6.68. Check the voltage on pins 4 and 8 of the op amp again that should be a good 9v.

[therealfindo]

OK.. having now measured the regulator  it doesn't seem to be the problem, as I'm getting 6.68 on one side (closest to jacks.. the regulator input, yeah?) and 3.11 on the pin closest to the top.. I also tried swapping it out for a new one.. still getting distortion with the hot-pickups. I can't really notice it with my other Tele..

Ok, now something doesn't sound correct there, the 3.3v reg should of course give out 3.3v but on the input to it you should be reading 9v or there abouts not the 6.68. Check the voltage on pins 4 and 8 of the op amp again that should be a good 9v.

I'm getting 6.93

The PSU (read at the jack) is 8.74

[Ice-9]

OK.. having now measured the regulator  it doesn't seem to be the problem, as I'm getting 6.68 on one side (closest to jacks.. the regulator input, yeah?) and 3.11 on the pin closest to the top.. I also tried swapping it out for a new one.. still getting distortion with the hot-pickups. I can't really notice it with my other Tele..

Ok, now something doesn't sound correct there, the 3.3v reg should of course give out 3.3v but on the input to it you should be reading 9v or there abouts not the 6.68. Check the voltage on pins 4 and 8 of the op amp again that should be a good 9v.

I'm getting 6.93

The PSU (read at the jack) is 8.74

Yeah, there is a issue somewhere with these readings.

If you can measure your PSU voltage when not connected to anything to confirm its not dropping voltage when under load that would be handy for me.
Check the correct value of R2, it should be 33 ohms, if a large value like 330ohms or bigger has been placed there then that would account for the voltage drop.
If your PSU is putting 8.74 volts into the IRFD9024 measured from 'Drain to ground' then you should be getting 8.74v (maybe a very slight drop 8.72v) measured from 'Source to ground' (output).

If you don't get a reading that is the same (I believe you will be getting 6.68v) then you can remove R2 which will effectively remove all the effects circuitry from the power. re measure the voltage from Source to ground. They should now be the same voltage your psu is putting into the circuit. If your still low on voltage then the IRFD9024 or the zenner may be faulty.

I am just on my way out, but when I get back in I can go more deeply into this.

[therealfindo]

hmm..

I did the measurements on theIRFD9024 and there was over 1V drop (I forgot to write the exact measurement down), the same for both drain and source. Thinking that this confirmed my suspicion that I'd fried it earlier, I took it off again (yeah, it's ot going back on!) and tried one of the other set-ups:

2.
If you want to omit IRDF9024 and just have a diode to ground type protection then do the following

Solder a wire link/jumper in place of R1.
Solder a wire link from 'Drain' to 'Source' in place of TR1.
Fit a 1N4001 in TR1 position. ('Drain to gate' with diode stripe towards drain).
Leave D1 empty.
Fit R2 as normal.

Unfortunately it didn't fix the distortion (though it's almost liveable with my not-hot Tele..)


So the readings I'm getting now:
on the 1n4001: 8.73 same as psu
Still getting 6.95 at the reglator though

It doesn't matter that I'm using a blue LED, right?

[Ice-9]

hmm..

I did the measurements on theIRFD9024 and there was over 1V drop (I forgot to write the exact measurement down), the same for both drain and source. Thinking that this confirmed my suspicion that I'd fried it earlier, I took it off again (yeah, it's ot going back on!) and tried one of the other set-ups:

2.
If you want to omit IRDF9024 and just have a diode to ground type protection then do the following

Solder a wire link/jumper in place of R1.
Solder a wire link from 'Drain' to 'Source' in place of TR1.
Fit a 1N4001 in TR1 position. ('Drain to gate' with diode stripe towards drain).


Leave D1 empty.
Fit R2 as normal.

Unfortunately it didn't fix the distortion (though it's almost liveable with my not-hot Tele..)


So the readings I'm getting now:
on the 1n4001: 8.73 same as psu
Still getting 6.95 at the reglator though

It doesn't matter that I'm using a blue LED, right?

Blue LED should be ok but you may need to change the LED load resistor value for brightness.

You still have a problem as 6.95 volts is just totally wrong. The voltage at the reg input should be the same as the voltage you are putting in (ie appx 8.73v from your psu).  First of all I would not be happy with a 9v psu that does not put out at least 9v but lets stick with the 8.73v. My first test from here would be to try a different PSU or a battery and check the voltages and the sound of the effect for distortion.

If the input voltages are reliable then my next question would be why is there a large voltage drop directly after the power input ? My answer would be that either there is a short somewhere, a faulty component or wrong value component fitted. My first check for incorrect components would be R2, it should be anything from 0 to 50 ohms (33 ohms is the size I use) if by accident you have fitted a 330 ohm or 3k3 resistor it will drop the voltage in a big way (simple ohms law here) so please check this is the right size resistor or just bypass it with a link wire to make it zero ohms and re-test the voltage at the regulator or pin 8 of the TL072.

Something is dropping the 9v line by over 2 volts meaning there is something wrong with a component or value somewhere. Let me know what you get when you check out what I have mentioned above.

[therealfindo]

ok, so I changed PSU to one which is putting out 9.09v

the 1n4001 is reading 9.07

now I'm not sure if this is corct, but I putt the black terminal at the + end of the diode and then read both ends of r2 - the end closest  to the footswitch gave 9.07 and the other end gave 6.39 which is the same as what I'm getting at the regulator.
So, I used an aligator clip to bypass it, as you said, and I got exactly 9.0 at the regulator input, and 3.2 coming out of it. In fact, I even saw the LED brighten when I did clipped the lead on.
What does R2 do, btw?
Now, R2 is definitely a 33ohm resistor (the second one I've used there in fact) according to the stripes: orange orange black, and I measured one from the same batch, and got 35...

[slacker]

I might be missing something but 6.39 Volts after R2 doesn't look unreasonable. The FV1 can draw about 70ma which would give about 2.5 Volts dropped across 33 Ohms.
Where is the opamp powered from? It's not shown on the schematics in Mick's first post, if it's running on 6.3 Volts it's probably that that's distorting.

[Ice-9]

I might be missing something but 6.39 Volts after the R2 doesn't look unreasonable. The FV1 can draw about 70ma which would give about 2.5 Volts dropped across 33 Ohms.

The supply to the FV-1 is after a regulator, the voltage at R2 should be appx the same as the 9v input. Unless there is some sort of extra drain on the circuit through a short or other problem the input voltage to the op-amp and other 9v circuitry should be appx 9v. The FV-1 control pots runs from 3.3v to gnd so a short across one of those could cause a problem, but I am trying to address this from the psu input first and follow the power through the circuit until we find the problem.  I'm not sure where the problem is at the moment but I am sure it will come to light and sorted. 

[slacker]

You can't have 70ma  coming out of the regulator without 70ma going into it, that's got to go through R2. I can't see how you can't be dropping any Voltage across it.
Even if the FV1 was only drawing the minimum specified current of 40ma you'd get a bit over 1 Volt across R2.

[Ice-9]

You can't have 70ma  coming out of the regulator without 70ma going into it, that's got to go through R2. I can't see how you can't be dropping any Voltage across it.
Even if the FV1 was only drawing the minimum specified current of 40ma you'd get a bit over 1 Volt across R2.

Yes of course you are correct, there will be a voltage drop the entire circuit is drawing appx 50ma at 8.7v and 33 ohms a voltage drop of about 2.2 volts.     So if as I suggest earlier that the 33 ohm resistor is shorted out/bypassed then this should correct the voltage drop for testing purposes.

All the other effects I have built to date do not suffer from any distortion so I am still wondering if that is or is not the problem here ?

[Ice-9]

ok, so I changed PSU to one which is putting out 9.09v

the 1n4001 is reading 9.07

now I'm not sure if this is corct, but I putt the black terminal at the + end of the diode and then read both ends of r2 - the end closest  to the footswitch gave 9.07 and the other end gave 6.39 which is the same as what I'm getting at the regulator.
So, I used an aligator clip to bypass it, as you said, and I got exactly 9.0 at the regulator input, and 3.2 coming out of it. In fact, I even saw the LED brighten when I did clipped the lead on.
What does R2 do, btw?
Now, R2 is definitely a 33ohm resistor (the second one I've used there in fact) according to the stripes: orange orange black, and I measured one from the same batch, and got 35...

Ok, that's good news. It would seem because of how much current the total circuit draws that a 33 ohm resistor is way to high and does cause too much voltage drop across it.
How is the distortion problem with R2 bypassed ? I will do some checks tomorrow but as of now I have not ha any clipping problems in all the builds. It could be that a high output pickup may clip the op amp when it is powered by a lower supply voltage of 6 ish volts.
I hope this gets to the bottom of the problem.

[therealfindo]

Oh dear... things just got much worse.

When I tried the effect with (with the alligator clip in place) I got a very nasty loud white noise explosion.. does the same without the aligator clip now. I also don't know if the regulator should be getting too hot to touch, but it is... eek.. not sure what happened!! Without the output plugged in, the voltage readings are the same as before.

[Ice-9]

Oh dear... things just got much worse.

When I tried the effect with (with the alligator clip in place) I got a very nasty loud white noise explosion.. does the same without the aligator clip now. I also don't know if the regulator should be getting too hot to touch, but it is... eek.. not sure what happened!! Without the output plugged in, the voltage readings are the same as before.

Ohh that doesn't sound good, where did you put the alligator clips ?

[therealfindo]

Ohh that doesn't sound good, where did you put the alligator clips ?

On the two legs of R2. I've looked for solder bridges, and other bits I might have bumped, but I can't see what has changed to make it do this...

I'm assuming that a bunch of voltage is getting into the guitar signal, right?
What should the op-amp readings be?

What does R2 do?

btw, thanks for all your help with this!!

[Ice-9]

The 3.3v reg should not be hot, so for now I would not connect power until we can find out what is wrong in case it may cause damage to other parts of the circuit.
R2 is just to help filter out any noise that might be present on the PSU supply line, R2 is not needed in the circuit for it to operate correctly, so bypassing it with a wire link should have no effect other than to raise the voltage going to the rest of the circuit.
is it possible to post a picture with your alligator clips in place a picture might shed more light on what is going on.
If all else fails to get this up and running I would be happy to take a look at it if you wanted to send it to me.

[therealfindo]

I'll try and get a pic in the morning, but the problem is the same without the alligator clip as well.. lots of nasty noise and a very hot regulator.
I can recheck the solder joints on all the spots around the polarity protection which I've been messing with tonight.

So strange...

[Ice-9]

I'll try and get a pic in the morning, but the problem is the same without the alligator clip as well.. lots of nasty noise and a very hot regulator.
I can recheck the solder joints on all the spots around the polarity protection which I've been messing with tonight.

So strange...

What worries me is that if the voltage regulator has now been damaged and if the unit is powered up again the FV-1 chip might get the full voltage of the PSU which in turn will  damage the FV-1. So if you can get me a picture so that I can see what was modified around the psu section it may shed some light on what is going on.
Thanks

[therealfindo]

ok, here's some photos of what it looks like... the desoldering (twice) of the mosfet wasnot pretty..

click for bigger:








This is where I had the aligator clips:

[Ice-9]

Thanks for the pictures, the re working of the power section looks ok and the crock clips look ok. I see you have the 3.3v reg in a socket, That's good as you can remove it from the PCB while testing the rest of the board.

With the 3.3v reg removed can you now recheck the voltages on the opamp. with R2 replaced by a link you should be getting the full input voltage between pin 8 and 4.

If your voltages are correct at this point you could uses an audio probe to follow the signal through the opamps to the output.(as the FV-1 won't be powered it can be bypassed) or a link between the negative side of C6 to the + side of C8. This will pass the signal through the analogue part of the circuit from the input jack to the output jack. Once that is all checked and ok next check the regulator is still working, best to check on breadboard first for 3.3v

[therealfindo]

So..

with the regulator removed, the op-amp 4 & 8 is giving me the same as the input psu 9.12 - here's the wierd thing, it's exactly the same  ( ok, maybe 0.02 difference) when I DON'T have the alligator clip.. so the 33 Ohm resistor isn't causing a voltage drop when the regulator is removed...

Now the regulator I tested on a breadboard: it is not heating up anymore, the out put is 3.23 but the input voltage drops to 9.06 (this is the same for 3 regulators - two that I'd tried in the circuit earlier and an unused one)