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I got .06v on the 47r resistor. Also, just to make sure I’m testing correctly:



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Ok so I think I was doing that wrong, sorry. Black tip to ground and red tip to the right leads of both of those resistors gets me full voltage.

Yep, you were doing it wrong--you were measuring the voltage drop across the resistor doing it that way.

Were the earlier transistor voltages taken correctly? They looked like they were.

_________________
“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2

Could you please check the resistance across the two solder joints for each of the three electrolytic caps? Since the leads are so close together on those, we occasionally will see some conductivity between them, leading to power loss. It's possible to get solder bridging between the eyelets in between the bottom of the cap and the PCB, analogous to what you found on the toggle switch.

_________________
“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2

One other thing--if your multimeter has a diode test function (arrow with a line across the point), please measure the forward voltage threshold on D1. Do that by disconnecting your power source and placing the black probe on the square solder pad o the diode and the red one on the round pad. Should come up in the 0.5 - 0.6V range.

_________________
“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2

For when you get that far with the pedal, you may find that you want to play around with the bias voltage on the Q2 collector. This voltage is determined by the combination of your power source (obviously!), and the series resistance of R5 (330 ohms), VR2 (the 10K Bias pot) and R6 (4.7 Kohms). This translates to a nominal resistance range of ~5.0 - 15.0 Kohms between the source voltage and the Q2 collector, depending upon the setting of the Bias pot.

On my own CF, I find that I get the best fuzz tone (this is highly subjective, obviously) with the collector biased to between 5.0 and 6.2 VDC. That happens with the combined resistance of these three components in the range of 5.6K - 7.5K. However, since the minimum resistance is 5.0K (Bias pot all the CW), I found that the most useful range of the Bias pot was in the last 25% of its sweep. Since I like to have the "sweet spot" more toward the middle of the sweep, I changed the value of the R6 resistor to 2.2K. This changed the sweet spot to between 12 noon and 2 o'clock and added some fuller, rounder sounding fuzz tones to the CW end of the sweep, where the bias voltage on the collector gets up around 8V.

Now keep in mind that these values are for my particular pedal and another Classic Fuzz may behave somewhat differently due to variations in components, mainly the transistors and pots. But the trends should be the same directionally.

_________________
“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2

Ok so I’m back at it today - the first transistor voltage test you had me do was done correctly, I just had a brain fart last night.

The diode test is reading .697.

I’m having a little trouble testing the resistance on the caps. I’ll get back to you in a sec.

Ok cool I get what you’re saying with the bias voltage. Great info to know.

When checking the resistance of the caps, should the pedal be on or off? Does it matter which side the probes are on?


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Sorry, should have specified--pedal off, power source disconnected. Doesn't mater which probe is on which side for resistance.

BTW, something that you should be aware of that isn't always obvious to novice builders: The effect circuit is always energized if the power source is connected and there's a cable inserted into the input jack. The footswitch is not an "on/off" power switch for the pedal; it merely switches the effect circuit in (engaged/LED on) and out (bypassed/LED off) of the signal chain. The LED is therefore an indicator of engaged vs. bypassed switch positions and not for whether or not the pedal is powered.

_________________
“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2

Ok, understood about power.

For the caps - I have the multimeter set on continuity mode, which I believe is also the lowest range for measuring Ohms? So with that, I get these readings:

2u2 - 001/beeping (solder bridge I guess?)
22u - 535
100u - jumps around all over the place, but seems to want to stay around 590

OK, looks like you need to pull the 2.2uf, clean up the solder bridge and then either reinstall or replace it. I'm thinking that this bridging occurred when you attempted to repair the defective EQ switching and reflowed the solder joints. I'm hopeful that this shorted cap may be at the root of your problem and correcting it will fix the pedal. But we'll see....

The other two look caps like they're OK. Confirm that there's no continuity between the 2.2's eyelet once reinstalled.

Have you removed and cleaned up the EQ toggle switch yet? If not, please do that, too.

_________________
“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2

Nope, will do both tonight.

Good. BTW, that 2.2uf cap is the one that is currently permanently connected to the effect circuit through the solder bridge under that toggle switch. Keeping my fingers crossed that fixing the two bridges will get you squared away!

_________________
“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2

Couldn’t get to it tonight, probably going to have to wait a couple days. I’ll get back to you when I get to it. Thanks again for all your help!

Back at it tonight. 2u2 came off fairly easy, but the switch took almost an hour to get off! Question - should I test the switch to fake sure I didn’t fry it with too much heat? How would I do that if so?

Do a continuity test on the switch in all three positions. In the middle position, there should be no continuity between the middle lug and either of the outside lugs. With the switch to the left, there should be continuity between the middle lug and the lug on the right side, but no continuity to the lug on the left. With the switch to the right side, the results should be just the opposite.

_________________
“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2

Hey just letting you know - the classic fuzz now works... mostly haha. The volume pot and gain pot are acting strange. The volume pot is cutting in and out, and the gain pot doesn’t start overdriving until about 2/3 o’clock.

I’m going to take a break from this pedal to finish off a couple others I’ve been working on, I’ll probably get back to it next week. I just wanted to say thank you for your time and patience, I appreciate your help. I learned a lot! I also would like to ask - any good resources out there for learning the troubleshooting side of pedals, reading schematics, that kind of thing?