Lead Solder Buzz
- Thread starter jimilee
- Start date
andrewsrea
Well-known member
That is 100% a bad charge pump IC4 - TC1044SCPA). Easy check is to remove IC4 (I socket all my ICs and transistors for this reason) and the pedal will then only be operating on your 9V supply and the square-wave oscillation will be gone.
Rationale: There are a few charge pumps which all have basically the same intent and pinout (TC1044, ICL7660, lT1054, etc.). Some versions are suitable for audio use and some are not. Also, some nefarious sellers from overseas will mark one of the ICs as the preferable type and it is actually the cheaper to make, non-audio version (eBay, Amazon).
They use an internal oscillator and capacitors to create a switching power supply, which doubles (or more, depending on the circuit) the voltage. The frequency to which they 'switch' is from 25kHz to 30Khz, just above audio frequencies. However, when they are not properly constructed they do not filter out the even-order sub-harmonics of the square-wave oscillator. What we are hearing on the clip you provided, is a 50Hz square wave sub harmonic.
I use ICL7660CPAZ and buy 10 at a time from Mouser (reliable source) for around $27 (2.70 each) delivered and have had no harmonic problems.
I've built two of the Lead Solder ODs and the only problem I have had has been since wave internal oscillations from too much gain, combined with the tone controls maxed and have posted a mod on this forum which prevents that by using lower values for R10 (510K) and C8 (200pF).
Hope this helps.
Rationale: There are a few charge pumps which all have basically the same intent and pinout (TC1044, ICL7660, lT1054, etc.). Some versions are suitable for audio use and some are not. Also, some nefarious sellers from overseas will mark one of the ICs as the preferable type and it is actually the cheaper to make, non-audio version (eBay, Amazon).
They use an internal oscillator and capacitors to create a switching power supply, which doubles (or more, depending on the circuit) the voltage. The frequency to which they 'switch' is from 25kHz to 30Khz, just above audio frequencies. However, when they are not properly constructed they do not filter out the even-order sub-harmonics of the square-wave oscillator. What we are hearing on the clip you provided, is a 50Hz square wave sub harmonic.
I use ICL7660CPAZ and buy 10 at a time from Mouser (reliable source) for around $27 (2.70 each) delivered and have had no harmonic problems.
I've built two of the Lead Solder ODs and the only problem I have had has been since wave internal oscillations from too much gain, combined with the tone controls maxed and have posted a mod on this forum which prevents that by using lower values for R10 (510K) and C8 (200pF).
Hope this helps.
jimilee
Well-known member
Changed all the caps. I’m telling you, this is a strange one.
comradehoser
Well-known member
Heed the words of prophecy--an easy idea to test, anyway.
jimilee
Well-known member
Will do, I missed that part, thank you.
jimilee
Well-known member
Well I don't have that noise anymore. I don't have any noise anymore, so I grounded pin 4 of the ICs, that wasn't helpful either. Stuck a 7660 in there, same buzz noise. I appreciate everyone help, this is a real mystery.
jimilee
Well-known member
Yessir, with no charge pump, it has no sound.
jimilee
Well-known member
I believe they’re nichikon. I get them from stompbox parts.
jimilee
Well-known member
Okie dokie. May be tomorrow. Thanks a tremendous amount.
I think it's just poor choice of values around the IC2 stage causing the IC to oscilate.
That's why changing C7 helped others. Good explanation in what's the simplest way I can't Google atm :
That's why changing C7 helped others. Good explanation in what's the simplest way I can't Google atm :
Taming the Oscillating Op Amp
Last week we looked at two very common reasons for oscillations or instability in op amp circuits. The ultimate cause of both was delay or phase shift in the...
e2e.ti.com
darwin999
Well-known member
I recently had a PCB where I was having issues, despite decades of soldering experience + quality solder. Realizing that I likely had a bad solder joint, I then visually re-checked &/or retouched every joint to no avail. But sometimes a solder joint will incorporate a small oxide layer that acts as a low-voltage diode in the circuit, but you won't find it with a DMM because it's measuring voltage biases the diode into conduction.
So I pulled out my trusty old 8 oz container of Superior No. 30 SuperSafe liquid soldering flux (https://superiorflux.com/products/superior-no-30-supersafe-soldering-flux/) which I used in my prior research life, and lightly put tiny drops on each PCB connection before resoldering them - and it totally fixed my issues. Supersafe #30 is a non-corrosive flux that rinses off completely with water or isopropyl. I know 'flux' is often considered a 4-letter word, as many of them are evil & corrosive - but this stuff is designed for and widely used in PCB assembly plants + research labs because it's so gentle on electronic components. It may be a little hard to find, but it's great stuff.
Might be worth a try at this point.
(I use the blue liquid, but it's also available as a paste.)
So I pulled out my trusty old 8 oz container of Superior No. 30 SuperSafe liquid soldering flux (https://superiorflux.com/products/superior-no-30-supersafe-soldering-flux/) which I used in my prior research life, and lightly put tiny drops on each PCB connection before resoldering them - and it totally fixed my issues. Supersafe #30 is a non-corrosive flux that rinses off completely with water or isopropyl. I know 'flux' is often considered a 4-letter word, as many of them are evil & corrosive - but this stuff is designed for and widely used in PCB assembly plants + research labs because it's so gentle on electronic components. It may be a little hard to find, but it's great stuff.
Might be worth a try at this point.
(I use the blue liquid, but it's also available as a paste.)
