May Queen II Trouble

[KevinHart]

I have just finished building a May Queen II from ROG site. All has gone well and boxed it up last night to give it a test.

Now I don't play the guitar as this project is for my brother! :oops:  I have borrowed a practice amp and conected this via the pedal to a keyboard headphone socket.

With the pedal on bypass I can get the amp and the keyboard set up to sound nice (I have a 100K volume pot in the line fom the keyboard to the pedal) :shock:

Now when I turn the effect on, first thing is that the volume drops significantly and I have to turn everything up to hear what is going on.  The sound then is 'squeaky'. I can hear some distortion, which rolls off as the level drops, so I think it is sort of working.  There is a significat amount of hiss too.

I have biased the FET to give 5.5V as shown on the schematic, but I only have 1.4V on the feed to the FET, but the drawing shows this should be 2V.  I also have 7.4V on the collector of the input transistor, which is fine.

So is this low voltage on the feed to the FET the problem or something else I should be looking at.  Is the us of an 'atificial sound' to the effect part of the problem??

Any help would be greatly appreciated as I only have till the 18th to finish the project!

[B Tremblay]

What FET did you use?

How are you powering the circuit?

Did you substitute any components?

[dv8]

Mine build with no substitutions from ROG schem worked fine and was plenty loud.  It's very distorted and trebly (well it is a treble booster).  Mine sounded comparable with sound samples on ROG.

Audio probe is a good start.

[KevinHart]

I am using a 9V battery and the fet is the J201.  I used different bipolar for the other two, but these were very comparable.

I do not have a signal probe or the knowledge of how to use it? I could create one using the keyboard headphone out?  What should I be looking for in its use? Applying at the inputs to the transistors and seeing if the signal is OK through to the amp??

[B Tremblay]

Look in the DIY FAQ at the top of this page and you'll find instructions for building an audio probe.  Your keyboard's headphone output will work perfectly.

Are you certain that your FET and transistor pinouts/orientation are correct?

Check that all places that should be ground are actually grounded.

[KevinHart]

OK I will go and have a check through and see what I can come up with.  Will let you know.  Thanks for the help so far!

[KevinHart]

Got it working! !!!

I had two problems, the FET was in wrong....mad as I studied the drawing a million times before putting it in as there were so many warnings to watch the pin outs on it! :oops:

Second problem was a dry joint on the input to the card...the very first conection, found it using my DMM. :oops:

Now I have a pedal hat works great, loads of Gain and treble lift.  The distortion is quite significant and there is a lot of Hiss. I modified the circuit by putting a gain control pot 100k in series with the 2.2uf cap. This seems to work well, but at full gain there is a lot of hiss...any ideas? Could it be a dodgy cap?  All the components are salvaged (except the semiconductors)  The cap was from an only SNES so only about 5years Old.

Any thoughts would be really helpful.  I will post some pics soon.

[msb69]

Got it working! !!!

I modified the circuit by putting a gain control pot 100k in series with the 2.2uf cap.

How exactly did you do this mod?  Is it worth doing?  Sounds pretty cool!

The only mod I did to mine was to add a DPDT toggle switch across the volume pot that lets me select between one of two caps to tame the treble from the pedal.

M