Rangefinder volume cleanup?

[Johnny]

I picked up a prebuilt Rangefinder and it is a great pedal. However, rolling back the volume to clean up the signal is not what it is with other pedals. I notice a big volume drop at about 9 on the guitar whereas without the RF, the signal is just less drive which what I expect.
Is this common for the RF? Seems like other Rangemaster TBs are supposed clean up very well with riding the volume.

 

[Big Monk]

I picked up a prebuilt Rangefinder and it is a great pedal. However, rolling back the volume to clean up the signal is not what it is with other pedals. I notice a big volume drop at about 9 on the guitar whereas without the RF, the signal is just less drive which what I expect.
Is this common for the RF? Seems like other Rangemaster TBs are supposed clean up very well with riding the volume.

What is the collector voltage? Did you change anything from stock?

IME, Rangemasters clean up just like Fuzz Faces when bias correctly.

 

[Johnny]

The voltage is 9.3. It is a Mullard OCP 71 transistor.
I did not change anything and it appears that all the correct parts were used in the build.

 

[Big Monk]

The voltage is 9.3. It is a Mullard OCP 71 transistor.
I did not change anything and it appears that all the correct parts were used in the build.

That's the collector voltage? What was the leakage on the transistor?

 

[Johnny]

Yes, Collector voltage. How would I measure leakage?

 

[Big Monk]

Yes, Collector voltage. How would I measure leakage?

What is your source voltage?

 

[Johnny]

If you mean what is coming through the power Jack 9.5 +/-

 

[Johnny]

Actually it’s 9.3.

 

[Big Monk]

If you mean what is coming through the power Jack 9.5 +/-

That collector voltage is very high. Seems like a leaky transistor. Rangemasters usually sound best in the 6-7 vDC range on the collector of the transistor.

Where did you source the transistor? Did they provide a leakage value?

http://www.geofex.com/article_folders/ffselect.htm

I would recommend one of the cheap TC1 component testers but in my experience they are only really accurate for low-medium leakage transistors.

Actually it’s 9.3.

Are you sure you are measuring at the right place?

 

[Johnny]

I did not build the pedal so not sure where parts are from.
I am measuring the source voltage at the power Jack “hot” lead.

 

[Big Monk]

I did not build the pedal so not sure where parts are from.
I am measuring the source voltage at the power Jack “hot” lead.

Where are you measuring the collector voltage?

 

[Johnny]

Where are you measuring the collector voltage?

On the left leg of the transistor- opposite of the leg shown on layout with tab.

 

[Big Monk]

On the left leg of the transistor- opposite of the leg shown on layout with tab.

And you are measuring 9.3 vDC there? Something seems off to me. With it at the source voltage, i'm surprised it makes noise at all.

 

[Johnny]

And you are measuring 9.3 vDC there? Something seems off to me. With it at the source voltage, i'm surprised it makes noise at all.

It is -9.3 on the display.

 

[Johnny]

update…tried a different meter and now I am getting 9.3 volts at the source and -6.95 on the Collector.

 

[spi]

the collector voltage seems good. Is there a buffer or another pedal between your guitar and the RF?

 

[Johnny]

the collector voltage seems good. Is there a buffer or another pedal between your guitar and the RF?

No. It is the first in line.

 

[spi]

Hmm, not sure what to suggest then. I had a rangemaster on my breadboard a few weeks ago but took it down--don't recall it having that issue, but also don't recall if I tested the volume roll off... likely I would've though.

 

[Big Monk]

A properly biased Rangemaster should have excellent volume rolloff.

Give the information you've provided, I don't "see" anything amiss.

Post some pictures of both sides of the board and we can help verify values, etc.

 

[Johnny]

Here’s pix of the board. Not able to do the underside right now. I do know that solder bridges and loose connections can occur on the best of builds, but this appears to be done very well.
3 of the resistors were placed with the values to the board making them unreadable.
The transistor is light sensitive, as expected. While I had it open to adjust bias, it would make noise in the light and go away when covered.
The IC is a 7660S.