HIGHWAY 89 PROBLEM

[HOTGUIT]

Hi
I built the HW89 overdrive, great tone and huge drive but I've a little problem with the vol pot.
the vol pot works properly in the first half only; after the mid point the level doesn't go up any more. Or better, the maximum level output is reached at pot's mid point; turning the pot to the second half no level increase is heard.
Why? The pedal is wired properly.
And then the pedal has a too much output level, how can I decrease it a bit?
I put a res in series with vol pot pin 3 but it doesn't work too much.
I used MarkM layout.
Anybody can help me?
thanks
bye
Hot.

[theehman]

Did you use a linear or audio pot?

[oldrocker]

+1

[snoof]

You might try a reverse audio taper pot if the crkt call for audio taper.  Or you try try custom tapering it using info from R.G.'s article "secret life of pots".  To lower the output I believe that you could try using a 250k or 100k vol pot.  It might interfere with the freq responce though, I don't know.  Doesn't the vol pot help to determine the output impedance??

[John Lyons]

This has been gone over a lot...search for it.

At any rate. Try a 10K-A (log) pot or even a reverse audio for the gain pot (as mentioned above).
You can also try a 100K-A pot for the level although there is still a large output with that.
Raising R14 to 2K may help as well.

Depending on which amp you use, the volume level changes.
Slightly broken up amp will give you less volume and more compression/gain.
Super clean amp will give you more straight level increase.

John

[DougH]

If none of that works to your satisfaction, replace the gain pot with a fixed 10k resistor, remove the cap (.0068?) that was connected to the collector, connect the cap that was connected to the wiper to the collector/10k node, and replace the 1M shunt resistor after the tone control with a 1M log pot. I can't remember the resistor number as I don't have the schematic handy.

[John Lyons]

I think you'll get a better range of control with this 1M divider arrangement anyway. (described above)

John

[HOTGUIT]

volume pot is a  A500 K.
I can't understand why it works in the first half only.
It is connected as usual, lug 1 to ground, lug 2 to output and lug 3 to signal 
any idea?

[PerroGrande]

Pull the potentiometer out of the circuit and test it.  Perhaps it is defective and reaching the 100% point too early. 

[DougH]

Oh, I thought you were talking about the gain control, not the volume pot.

Never mind...

[HOTGUIT]

No problem Dough,
Thank you Perro i'll try it
bye
hot