Build Your Own Clone Message Board

Hi, I have completed a Lil Fuzz, but it's not working quite as expected. The LED comes on when engaged, and it passes signal fine in bypass. However when engaged it only passes a very low signal of spitting and noise. I have tried to change the bias pot but it doesn't seem to help any. I have a signal tester and would be happy to chase the path if you have a map with the order the signal passes. Thanks for your help!

Could we see the solder side of the PCB?

Are you sure that you have the two pots in the correct positions and not switched?

Were you able to get 4.5 - 5V on the Q2 collector by adjusting the trimpot as per page 9 of the instructions?

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

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

Thanks for your quick help! I can confirm that the pots are attached to their matching labels on the board. I wasn't 100% sure which leg was the collector, but I wasn't able to much change out of any of them. I think I was close to 9V on the lower leg of the transistor no matter what I turned on the bias pot. It seemed suspect that the pot didn't seem to do anything, but I wasn't totally sure I was doing the measurement right. I'm happy to rerun the test though. Thanks again!

The collector of Q2 is the bottom leg of the transistor adjacent to the trimpot. That should optimally have 4.5 - 5V of DC voltage on it.

I would recommend a complete reflow on all the solder joints, because of how often it solves problems like this: viewtopic.php?f=9&t=52188

BTW, that's the wrong value resistor just above the LED--should be a 4.7K and it's a 47K. It has nothing to do with your problem, but the LED will be pretty dim with that much resistance on it.

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

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

Wow good catch! You are correct, that is not the resistor it's supposed to be. I'm guessing that was an error in the kit. No big deal though, the LED Is bright enough - if I come up with a spare 4k7 resistor I can swap it out. I'll reflow everything and see if anything changes. I reflowed most of them already, but I'll make sure I hit everything.

After a complete reflow the behavior is the same. I suspect that the bias pot is not working as expected.

I'm getting 8.91 Volts in from the power supply. From the output of the bias as well as the collector of the transistor I read 8.65 Volts all the way to the left, and 8.91 Volts all the way to the right. I'm open to your suggestions.

Also I can confirm the LED is pretty dim! I did confirm that all of the other resistors match their intended values.

Thanks again for you help!

The bias trimmer value should be stamped on the side of the pot. Can you read what it says?

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Please do not PM me. email is prefered. keith@buildyourownclone.com

I believe it says 25k5 5M

I would suspect that the problem has more to do with your transistors than the trimpot. Please contact sales@buildyourownclone.com for a replacement set.

_________________
*patience is a virtue*

Please do not PM me. email is prefered. keith@buildyourownclone.com

I received a pair of new transistors and a 4.7k resistor to help with this. The resistor changeout certainly did do the right thing as the LED is much brighter now, but the signal problem persists. When in bypass it works perfect, when engaged for a short time it would make some spitting noises, but now does not. I'm very grateful for the swapout of parts, but given that didn't do it, I'm inclined to troubleshoot further if we can. I have a signal tester and a multimeter and would be happy to test, I'm just not sure what I should do next. Could you give me the signal path test order? I'd be happy to chase it to make sure I'm not losing it right out of the switch or something like that. Thanks much!

The main signal path is linear and should be fairly obvious if you take a look at the schematic. It goes from the tip of the in jack > lug 4 of the footswitch > lug 5 of the footswtich > C1 > Q1 > Q2 > trimpot > C3 > volume pot > lug 7 > lug 8 > tip of the output jack.

_________________
*patience is a virtue*

Please do not PM me. email is prefered. keith@buildyourownclone.com

If I'm reading right, OP had a 47k CLR that got replaced with the standard 4k7, so I think that explains the increase in brightness.

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Scott

My band, Austin Hollow

I meant to type transistor. In addition to that mistake, I read resistor as transistor in the OP's last post. So completely disregard that statement. I removed it from my last post.

_________________
*patience is a virtue*

Please do not PM me. email is prefered. keith@buildyourownclone.com

Thanks, this was very helpful. I can confirm the signal is good all the way up to the input of Q1. After then I don't get anything. Is there anything else I can do to confirm the transistor is working as expected (or whatever else you suggest). Thanks much!

Please take voltages of both transistors.

_________________
*patience is a virtue*

Please do not PM me. email is prefered. keith@buildyourownclone.com

Thanks for your help. I spent time over the weekend checking continuity, signal path, and reflowing components, but was unable to find anything else wrong on my own.

I'm not sure how to name the 3 legs, but these are the voltages as measured from the back of the PCB where the legs are exposed. All pots are turned fully to the right.

Q1 (closest to the foot switch)
Left. 8.62
Center. 7.62
Right. 0

Q2
Top. 8.36
Center. 8.62
Bottom. 8.90

Thanks again!

Those voltages are quite a bit off. Q1 is biased by the 100k resistor that connects to the emitter of Q2 (feed forward biasing), so I'd actually be more inclined to think the problem is with Q2 rather than Q1. Please contact sales@buildyourownclone.com and we'll get a new set of transistors out to you.

_________________
*patience is a virtue*

Please do not PM me. email is prefered. keith@buildyourownclone.com

Just to be sure, we already replaced the transistors once already. I'm happy to do again, but wanted to make sure that was understood before we put a third set in the board. Thanks!

Hayley just notified me of this. Maybe it's not the transistors then.

When you take voltage readings, do you have the bias trimmer set at about noon?

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*patience is a virtue*

Please do not PM me. email is prefered. keith@buildyourownclone.com

No, was set all the way to the right, I can take another reading at noon though. I'll post here shortly.

With trim about noon here are the results:

Q1 (closest to the foot switch)
Left. 8.62
Center. 7.62
Right. 0

Q2
Top. 8.37
Center. 8.62
Bottom. 8.82

With the Trim set all the way to the left

Q1 (closest to the foot switch)
Left. 8.62
Center. 7.62
Right. 0

Q2
Top. 8.36
Center. 8.62
Bottom. 8.66

Are you certain that you've reflowed the solder joints to the C1k fuzz pot as well, both on the PCB and the pot itself? It's very hard to tell on a circuit this simple, because one mistake at any of the components can throw everything out of whack, but it just seems that the problem is that Q2 isn't biasing correctly. We typically look at the collector of Q2 for these sort of problems, but maybe it's at the emitter, i.e., the resistance between the emitter and ground via the fuzz pot.

_________________
*patience is a virtue*

Please do not PM me. email is prefered. keith@buildyourownclone.com

I'm sorry this one is being frustrating. I reflowed all 6 points of contact on the fuzz C1k pot. With the bias about noon and both other pots full to the right I still get about the same readings (and results when plugged in).

Q2
Top. 8.38
Center. 8.64
Bottom. 8.80

I'm open to whatever is the best next step. Please let me know your suggestion. Thank you for your help!