DR Q build not working. Many Pictures included in link.

[pappasmurfsharem]

I built the Dr. Q using the layout at Tagboard effects at the bottom of this post, Jack Ormans schematic.

The google docs link is my shared drive with multiple pictures of the build I also have a few bottom side shots with a light shining through to see the spaces between traces.

I've tried TL072 , 4558, 5532 for the IC and tried multiple 2N3904's for the Tranny

for the Trimmer I used 30k and for the 50nF I used 47nF and for the 5nF I used 4700pF

I get clean signal which appears to come from the switch 1 and switch 5 connection.

The signal that hits the DIODE section appears to be the problem.

That section seems to just be producing noise. The noise is like a hum/buzz which does not change with guitar input. If I adjust the trimmer I hear the noise changing its frequency, but the "clean" signal doesn't appear to change much except at the very extremes of the trim pot.



https://docs.google.com/folder/d/0B1GdN249GMFFZWZodWVCZVhhaGM/edit

[Mark Hammer]

The Doctor Q requires a 1458 in order to sweep.  You might get away with an LM358 or some other functionally equivalent dual op-amp, but the ones you listed will NOT work.

It is because of that requirement that Jack Orman, bless his heart, came up with the little biasing fix he implemented in the Dr. Quack.  If you do not have an LM1458 handy, and don't feel like ordering one and waiting, do the Dr. Quack biasing trick.

[pappasmurfsharem]

The Doctor Q requires a 1458 in order to sweep.  You might get away with an LM358 or some other functionally equivalent dual op-amp, but the ones you listed will NOT work.

It is because of that requirement that Jack Orman, bless his heart, came up with the little biasing fix he implemented in the Dr. Quack.  If you do not have an LM1458 handy, and don't feel like ordering one and waiting, do the Dr. Quack biasing trick.

I have a few 1458's and I saw a previous thread where you stated basically the same thing, but would that potentially resolve the kind of results I am seeing?

[Mark Hammer]

Yes.  When I say it won't sweep, that is not because of the filter section, but rather because of the envelope follower section (i.e., the part with the diodes).

[pappasmurfsharem]

I'll try it out and report back. mirosol also pointed out that I ran my resistors in parallel. I've been coupling caps a lot recently and forgot they work opposite when it comes to series/parallel.

Sigh the little things....

[pappasmurfsharem]

Well using a 1458 and fixing the 2M resistor didn't resolve it.

In the envelope follower section where should I be hearing audio? If anywhere?

I only get sound using a probe up to the beggining of the 2M resistor

[drolo]

Well using a 1458 and fixing the 2M resistor didn't resolve it.

In the envelope follower section where should I be hearing audio? If anywhere?

I only get sound using a probe up to the beggining of the 2M resistor

unfortunately i have no access to google docs a my job. If my brain works correctly you should have some sort of very loud ugly distorted signal after the opamp in the envelope follower section. If you lose the signal after the feedback resistor, maybe the opamp is not functioning correctly. Possible leads would be the power supply. a bad/wrong connection error, bad solder joint, short

[Mark Hammer]

With your meter set to AC volts (if it has ranges, set to something that does a respectable job indicating AC voltages under 5V), and the circuit engaged, you should get an AC voltage at the wiper of the sensitivity pot, and at the output of the lower opamp just prior to the diode.  The first one will likely be something around 50-100mv when you strum, and the second one should be a couple of volts.

Now, set the meter to DC and measure on the other side of the diode.  That should be a little under half or so of what the AC output was on the op-amp.  If that checks out, your envelope follower is working fine.

Is the transistor pinout the same as the layout you are using?

Finally, if the filter section is fine, but the envelope-control is wonky, you should still be able to sweep the filter by adjusting the trimpot.  If you are not getting any sort of audio output that sounds like it is filtered, then the problem lies in the filter portion.

[pappasmurfsharem]

My cheapo MM has 200 and 700 setting in the V~ section.

Pin 1of the OP shows 17  can't get a reading on the wiper

[Mark Hammer]

Then you should check your connections, as well as the state of the pot.  Pots don't malfunction or break all that readily, but it does happen.

[pappasmurfsharem]

Then you should check your connections, as well as the state of the pot.  Pots don't malfunction or break all that readily, but it does happen.

The pot seems normal. The setting in the AC section doesn't have an m after it. So I assume the 17 on the opamp is 17v AC.

If the wiper is supposed to be in the mV wouldn't it just be lower than the AC capability of the meter?

[Mark Hammer]

The range of the meter indicates how high it can measure to and still show you something.

There is no way that the meter would read 17 volts unless you were powering the circuit with something more than that.  I assume you are powering it with 9vdc?

[pappasmurfsharem]

The range of the meter indicates how high it can measure to and still show you something.

There is no way that the meter would read 17 volts unless you were powering the circuit with something more than that.  I assume you are powering it with 9vdc?

I figured that seemed odd. So what does that 17 mean then?

[Mark Hammer]

That would depend if there was a decimal point to the left of the 1 or to the right of the 7!

[pappasmurfsharem]

That would depend if there was a decimal point to the left of the 1 or to the right of the 7!

There isn't one! ;-) or its to the right of the 7

[Mark Hammer]

Hmmm, perhaps you need a different meter, just to verify, since what you're getting presently is somewhat misdirecting.

If you set the meter to a DC range and test a battery, do you see a decimal?

[pappasmurfsharem]

Hmmm, perhaps you need a different meter, just to verify, since what you're getting presently is somewhat misdirecting.

If you set the meter to a DC range and test a battery, do you see a decimal?

The DC settings work fine and show decimals depending on the settings.

It has a 20mV, 200mV, 20V, 200V, 1000V settings the AC setting only has 200 and 700 settings