hekkmart wrote:
..Can you be more specific on how to "check resistance" on that 4.7k resistor, and the "left-lug continuity to ground" ? ..Not sure how to check that.
No problem.
Continuity Check: Two points in a circuit have continuity when they are directly connected with no significant source of resistance between them. In this case, we want to make sure that the left lug of the Bias pot doesn't have a direct or very low resistance connection to ground--if it does, your voltage will flow to ground rather than on through the 4.7K resistor to the Q2 collector. To check, disconnect power from the pedal and turn your multimeter to the continuity setting--it's at the low end of the resistance settings at the bottom of the dial, next to the "hFE" setting, and its icon looks like sound waves emanating from a point source. Now you just need to place one probe (doesn't matter which) on each test point, so one on the left lug of the pot and the other on ground (I'd stick with the sleeve of the input jack that you've been using). If there is continuity between them, the meter should give an audible "beep" sound; you can confirm this capability of the meter by just touching the probe tips together before you test on the pedal. If it's a non-beeping meter, just report the readout value you get.
Resistor Check: As I've thought about this, I've realized that a bad resistor in the R6 spot couldn't cause what you're seeing, so no need to do this. Still, it's a good thing to know how to do, so here's how. Leave the power disconnected from the pedal. Set the meter on the resistance setting that's the next higher value than your expected result--in this case, measuring a resistor of 4.7 Kohm nominal value, you'd set the meter to 20K. Then just touch the probes (again, it doesn't matter which) to the leads of the resistor and wait for the reading to stabilize. IMPORTANT: This method is often NOT reliable for resistors that are installed in a circuit! That's because of the very common occurrence of parallel circuit paths between the two points, which will lead to erroneously low resistance results. In this case, it works, but I don't recommend using the method generally, unless you have a very clear understanding of the circuit schematic you're working with. What this method is VERY useful for is verifying resistor values
before they're installed in a circuit.
BTW, I have the R6 resistor spot socketed in my own Classic Fuzz, so I pulled out the resistor to simulate no voltage coming through to the Q2 collector from the Bias pot. I then tested the voltage levels on the Q2 legs:
C = .27
B = .93
E = .27
Essentially identical to what you've reported!
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