Author Topic: Need some quick help with my Big Muff  (Read 312 times)

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seadi123

Need some quick help with my Big Muff
« on: January 13, 2018, 03:09:39 AM »
I need this pedal done today, the circuit is not completely dead when connected, but the volume is low with almost no gain, like clean sound. Voltages:
Q1 q2 q3 : 4.4v 0.14v 0.8v
Q4 : 4.8v 1v 1.4v
Diodes: 0.8v 0.6v

NYC Big Muff pi ec3003, 2n5088 trans, 1n4148 diodes

Layout : http://2.bp.blogspot.com/-dhrzj6JgnAQ/VDkrfpxRgZI/AAAAAAAAIpk/H-6aMtpt0CQ/s1600/EHX%2BNYC%2BBig%2BMuff.png

Schematic : http://4.bp.blogspot.com/-uYM0v6H2q-s/VDlz5ZgvKVI/AAAAAAAAIp0/N33_ifLfqf0/s1600/Big_Muff_PI_Ec-3003_ver_C_.png

I already ran a knife through the rails. Where should i look at?

Slowpoke101

Re: Need some quick help with my Big Muff
« Reply #1 on: January 13, 2018, 03:39:59 AM »
Your Base voltages on Q1, 2 & 3 are very low. The expected base voltage would be somewhere near 3.6 V. Check the values of the 470K resistors going from the Collectors to the Bases on those transistors.
Make sure that you have the transistors orientated correctly.
Some pictures would be very helpful too.


Edit: I am an idiot. The base voltages should be near 0.6V not 3.6V Your emitter voltages seem to be a bit higher than expected, 0.05V is to be expected. Sorry for the error.
« Last Edit: January 13, 2018, 03:52:50 AM by Slowpoke101 »
..

Elijah-Baley

Re: Need some quick help with my Big Muff
« Reply #2 on: January 13, 2018, 03:43:22 AM »
I write quickly. Check all the orientations. Check the value of the resistors. Check the position of the component, wires, cut track and jumpers.
«There is something even higher than the justice which you have been filled with. There is a human impulse known as mercy, a human act known as forgiveness.»
Elijah Baley in Isaac Asimov's The Cave Of Steel

slashandburn

Re: Need some quick help with my Big Muff
« Reply #3 on: January 13, 2018, 04:37:06 AM »
Did you flip your transistors? The pinout is different on the 5088s compared to the BC550 on the vero layout.

Failing that, photos would help.

seadi123

Re: Need some quick help with my Big Muff
« Reply #4 on: January 13, 2018, 07:42:39 AM »
I checked everything and didn't find the solution, but putting a ts9 in front of this sounded soo good and unique. So i'm just keeping this board and i'll build another one from scratch. Thanks everybody!

Plexi

Re: Need some quick help with my Big Muff
« Reply #5 on: January 13, 2018, 09:55:42 AM »
Post some photos of your board!
(Closer solder side )
To you, buffered bypass suck tone.
To me, it suck my balls.

seadi123

Re: Need some quick help with my Big Muff
« Reply #6 on: Yesterday at 07:44:51 AM »
Ok now i really need some help. I built the second board and got the exact same results: there's almost no gain, only with the sustain at maximum i do hear some fuzz, it's like a warm overdrive. I replaced the 2n5088 with 2n5089 assuming it was just that the transistors had low gain; same thing. I have double checked the orientantion and soldering and its all right. What should i look for?

EBK

Re: Need some quick help with my Big Muff
« Reply #7 on: Yesterday at 07:56:37 AM »
Failing that, photos would help.

Post some photos of your board!
(Closer solder side )

See above.   :icon_wink:
No affiliations. If I glowingly mention specific merchants or products, it is because I like them without having to be paid to like them.

seadi123

Re: Need some quick help with my Big Muff
« Reply #8 on: Yesterday at 08:17:00 AM »
Here's the copper side, looks terrible because i replaced the transistors, but i ran a knife through the rail so they're not touching: https://s13.postimg.org/q0f2op913/image.jpg

Here's my normal soldering job from the previous board: https://s13.postimg.org/3pr7oaoh3/image.jpg

Component side: https://s13.postimg.org/mgt4yyqwn/image.jpg

Component side from previous board: https://s13.postimg.org/qr7suftdz/image.jpg

I've also double checked resistors and pots values
« Last Edit: Yesterday at 08:20:20 AM by seadi123 »

Elijah-Baley

Re: Need some quick help with my Big Muff
« Reply #9 on: Yesterday at 09:18:52 AM »
Component side: https://s13.postimg.org/mgt4yyqwn/image.jpg
I'm seeing the diodes in the centre of the board. I guess them should be in anti-parallel.
«There is something even higher than the justice which you have been filled with. There is a human impulse known as mercy, a human act known as forgiveness.»
Elijah Baley in Isaac Asimov's The Cave Of Steel

duck_arse

Re: Need some quick help with my Big Muff
« Reply #10 on: Yesterday at 09:28:42 AM »
^ me too.

just for the educational value - can you measure the resistance of all your 120R resistors, and all your 10k resistors? and, funny colours/light, can you also measure the resistance of the 27k in the middle of the board?
"Here they call me Macgyver I can do everything with nothing" - GiovannyS10

"dags, etc" - Slowpoke101

sorry, I must have pushed the wrong button.

seadi123

Re: Need some quick help with my Big Muff
« Reply #11 on: Yesterday at 09:32:32 AM »
Component side: https://s13.postimg.org/mgt4yyqwn/image.jpg
I'm seeing the diodes in the centre of the board. I guess them should be in anti-parallel.

Nice catch! Will flip one now

seadi123

Re: Need some quick help with my Big Muff
« Reply #12 on: Yesterday at 11:24:42 AM »
Flipped the diode, now i hear fuzz only with all knobs turned up full. The volume is low, with volume in half i almost cant hear anything. Tone pot is ok, fuzz also works but there is no aggressive distortion whatsoever.

seadi123

Re: Need some quick help with my Big Muff
« Reply #13 on: Yesterday at 11:26:43 AM »
^ me too.

just for the educational value - can you measure the resistance of all your 120R resistors, and all your 10k resistors? and, funny colours/light, can you also measure the resistance of the 27k in the middle of the board?

Also measured 120ohm and 27k resistors, everything is fine. It's also intriguing that i have the same problem on both the boards i've built, it's like i've done the same mistake twice

seadi123

Re: Need some quick help with my Big Muff
« Reply #14 on: Yesterday at 11:43:58 AM »
Additional info: I've used the upper ground rail of the muff as a ground point for everything. This is a 2 in 1 pedal, the other effect works fine and true bypass also works fine