Fuzzrite help needed

Mr. Bill
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Re: Fuzzrite help needed

Postby Mr. Bill » Thu Feb 10, 2011 10:27 am

I'd start by using the lowest scale that your meter has. You want to be sure that the contacts show as little resistance as possible. At the lowest scale most meters will not actually read 0 (zero), as they will normally show the resistance of the two test leads.

Turn off the battery switch, and unplug the guitar cables for these tests. To test the footswitch, touch one lead to the center two terminals. Now touch the other meter lead to each of the two right side terminals. You should get either a zero reading or an open (infinity) reading at each of the two terminals. Now push the switch button and repeat the test . The readings should be the reverse of what you got the first time. Depending on what position the switch is in there should be continuity from the center terminal to either the left or the right terminal of the switch. Because the two center terminals are connected together, the switch will connect the center terminals to both the top right and lower right terminals of the switch.

Repeat the test from the center terminals to the left two terminals.

Retest the reading across the outer lugs of the volume pot. 0.014 on a 2M scale would be 14K. What value volume pot is in there right now?

E9th
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Re: Fuzzrite help needed

Postby E9th » Thu Feb 10, 2011 4:28 pm

at full volume, the volume pot seems to measure consistently half of whatever value the pot installed is.
when i had a 350K in there it read 180K, now that there is a 33K in there it reads 14K. when i took the 350K out of the circuit it again measures 350K. remember that i have resisitors placed across the outer lugs of these pots to bring them down from 500K to 350K and 50K to 33K. I used 1.2 M resisitor for the 500K and 100K for the 50K.

I will test the footswitch as soon as I can.

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Re: Fuzzrite help needed

Postby E9th » Fri Feb 11, 2011 7:45 am

with battery switch set to off and no chords plugged in :
meter set to 2K I get 1 with the probes touching nothing, touching the probes together I get 0.
with one probe on the cente and the other on the right lug of the footswitch I get 1, when I depress the footswitch i get 0.
It performs as you said it should for both right and left sets of lugs.
volume measures 15K

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Re: Fuzzrite help needed

Postby Mr. Bill » Fri Feb 11, 2011 11:51 am

at full volume, the volume pot seems to measure consistently half of whatever value the pot installed is.
This doesn't seem to make sense. While taking reading across the outer terminals of the volume control, try adjusting the depth pot. Try switching the footswitch. Do this with power off and no cables in jacks.

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Re: Fuzzrite help needed

Postby E9th » Sat Feb 12, 2011 8:03 am

with battery to off and no cables plugged in, footswitch off, across the outer lugs of the volume pot i get:
13K, tunring the depth knob all the way I get 13.9K.
I get the same readings with the battery switch on.

with footswitch ON I get 29.9K.
This is on the 50K pot with 100K resistor to emulate 33K pot.

I could put the 350K back in , but it seemed to make no differnece before
:?

In this picture you cant really see well but there is a green wire going from the lowest board terminal to the battery switch.
Is this correct? it was hard to tell from the photos I was working from.
Image

Mr. Bill
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Re: Fuzzrite help needed

Postby Mr. Bill » Mon Feb 14, 2011 1:02 pm

The wire from the battery switch is wired correctly. The resistance readings are are making a little more sense now. If your output level is still low, then there may be a problem on the board itself.

There could be a bad resistor or a bad cap or even a bad transistor. I'd start by reading the resistances of the resistors on the board. There are 4 - 470K ohm and 1 - 22K. Check them to see what you get, power off. Unless your meter can read capacitance there is no easy way to test the caps other than by substitution. Do you have any small value caps on hand that can be used as subs or to parallel the existing ones?

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Re: Fuzzrite help needed

Postby E9th » Tue Feb 15, 2011 7:09 am

I get 520K on three and 550K on one on the 470K's, and then I get 24K on the 22K.
With the components still attached to the board and other components, would this be enough drift to cause the volume drop?

thanks for the help

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Re: Fuzzrite help needed

Postby Mr. Bill » Tue Feb 15, 2011 11:38 am

They are out of tolerance, but my first inclination would be elsewhere. Do you have any small caps around?

Try this, unsolder one end of the 22K resistor. Now try the pedal is there more volume now?

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Re: Fuzzrite help needed

Postby E9th » Fri Feb 18, 2011 3:59 pm

Thanks Mr. Bill, I was down and out with food poisoning for a while. Been a rough 2011 thus far for me. But I should be able to get to this this weekend. I have some small ceramics caps but not sure of the values, They are probably suitable for guitar tone pots, I'll have to check.

Does it matter which end of the 22K resistor i lift?

Thanks again.

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Re: Fuzzrite help needed

Postby Mr. Bill » Sat Feb 19, 2011 11:44 am

Sorry to hear that. It has been a bad year.

Lift either side of the 22K, and see if the volume increases.
If you have a 0.05 or a 0.02 tone control cap, that will work fine for what I want you to check.


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