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PostPosted: Sat Oct 15, 2022 11:47 am 
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Hi,
I just recently finished a SP2 build. Almost everything works as it should - all pots function, LEDs come on, bypass works, and the boost channel works properly. On the drive side, however, I get this odd buzzing/distorted sound that appears as the notes are decaying. It happens more when the drive is pushed harder. I don't notice the sound at the first attack of a note, or if I play a note and mute it immediately. But when I let everything ring, amidst all the swirling and other sounds you'd expect, this weird buzzing/crackly/distorted sound appears, then cuts out before the "proper" sound completely decays. Without anything to compare it to, I'm not 100% sure this isn't normal, but it seems unlikely.

I have rechecked all my component values and tried different ICs in each position. I've used multiple power supplies, cables, guitars, and amps. Any ideas where I should go from here? Thank you!

Pic:
https://drive.google.com/file/d/183eDc6 ... sp=sharing


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PostPosted: Sat Oct 15, 2022 1:57 pm 
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That's a good looking build and I don't see anything out of place, so a set of DC pin voltages for all four IC's would be a good next step. In case you're not familiar with how to take those:

Set your multimeter to the DC voltage mode, indicated by a solid line above a dotted one. Use the 20VDC range setting if it's not an auto-ranging meter. Your power source needs to be connected and there needs to be a cable in the input jack. If the pedal is assembled into the metal enclosure, put the black probe into one of the corner screw bosses of the enclosure--this is your ground connection. If the "guts" are out of the enclosure, use the sleeve tab of the input jack for the ground connection. Then touch the red probe to each point that you want to measure. See image below for the numbering of the pins.

Image

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PostPosted: Sun Oct 16, 2022 4:58 pm 
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IC Voltages:

Leftmost IC:

Pins
1) 4.78
2) 4.78
3) 3.76
4) 0.0
5) 4.77
6) 4.78
7) 4.78
8.) 9.50

Center IC:

1) 9.49
2) 9.49
3) 0.0
4) .007
5) 0.48
6) 0.0
7) .002
8.) 9.50

Rightmost IC

1) 4.78
2) 4.78
3. 4.78
4) 0.48
5) 4.78
6) 4.78
7) 4.79
8.) 8.36

Thanks for your help!


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PostPosted: Sun Oct 16, 2022 8:56 pm 
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Your left side IC (TL072) looks fine, but the center IC (the LT1054 charge pump) appears clearly defective and since it feeds the right side TL072, that one has some wrong voltages, too. The voltages for the ICs on the fully functional overdrive side of my SP2 are shown below as a comparison. Note that some of the voltages are actually negative, since this is how the charge pump works. You should contact sales@buildyourownclone.com and request a free replacement for your charge pump. Tell 'em DVM sent you.

Good looking build, BTW.

Attachment:
SPII_OD_IC_voltages.jpg
SPII_OD_IC_voltages.jpg [ 20.87 KiB | Viewed 1016 times ]

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PostPosted: Mon Oct 17, 2022 6:02 am 
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Hi,
I did not take voltages for the charge pump. My voltages were from the 3 op amps - but I see the confusion since that rightmost op amp is for the boost channel. What you have listed as "Right IC" is what I listed as "Center IC". Either way, the voltages for this one are off. I did switch out that LT1054 and it did not fix the sound I heard. However, I never took voltages on the LT1054 with either IC inserted. I will do this tonight. I'm wondering is there's an issue with the socket? Thanks!


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PostPosted: Mon Oct 17, 2022 9:55 am 
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Ah, OK--yes, I did interpret your readings as you said.

It still appears that something is going on with the charge pump, since the boost/right IC should also read with a negative voltage at pin 4 and a ~doubled voltage at pin 8--essentially identical to what I listed for the "right" IC. I would recommend taking these voltage readings:

  • The charge pump with all IC's installed
  • The charge pump with the middle IC out
  • The middle and right IC's with the charge pump out
  • The empty middle IC socket with the charge pump in
  • The empty middle IC socket with the charge pump out
  • The empty charge pump socket

A lot of measurements to take, I know, but hopefully the results will illuminate what's going on.

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PostPosted: Mon Oct 17, 2022 4:10 pm 
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The charge pump with all IC's installed
1. 9.51
2. 0.0
3. 0.0
4. 0.42
5. 0.43
6. 0.0
7. 0.0
8. 9.50

The charge pump with the middle IC out
1. 9.51
2. 0.0
3. 0.0
4. 0.39
5. 0.39
6. 0.0
7. .002
8. 9.51
The middle IC with the charge pump out
1. 7.33
2. 6.69
3. 6.66
4. 7.22
5. 6.64
6. 6.90
7. 7.32
8. 8.51

Right IC with charge pump out
1. 7.31
2. 6.90
3. 6.64
4. 7.22
5. 6.64
6. 6.68
7. 7.30
8. 8.51

The empty middle IC socket with the charge pump in
1. 4.60
2. 4.76
3. 4.78
4. 0.39
5. 4.78
6. 4.58
7. 4.60
8. 8.42

The empty middle IC socket with the charge pump out
1. 6.21
2. 6.44
3. 6.44
4. 7.04
5. 6.44
6. 6.15
7. 6.17
8. 8.51

The empty charge pump socket (I did this with all IC's installed)
1. 9.50
2. 0.045 (I watched the meter fall from 1 volt all the way down over the course of 2 minutes - might have kept falling if I continued)
3. 0.0
4. 0.12
5. 7.14
6. 0.0
7. 0.0
8. 9.50


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PostPosted: Tue Oct 25, 2022 4:43 pm 
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Hey duhvoodooman,
Thanks for your help so far. Just wanted to follow up - any ideas where I should go from here? Also, I see on the schematic that they number the components (R1, R2), but it's unclear where these coincide with the layout. Any direction on this? Thanks!


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PostPosted: Wed Oct 26, 2022 10:49 am 
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Have you replaced the charge pump yet?

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PostPosted: Wed Oct 26, 2022 11:30 am 
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Sorry for leaving you hanging for a week! :oops:

I've reviewed your voltage readings and also measured the same combinations on my own fully functional SP2. In all cases with the charge pump removed from its socket, our results agree closely, including the voltage readings on the empty charge pump socket. Analogously, the three sets of voltages with the charge pump installed do not agree, and are consistent with a bad/failed charge pump IC. My results in these three cases duplicate the values that I posted for the "Center" and "Right" IC's HERE.

Please contact sales@buildyourownclone.com and request a new, PRE-TESTED charge pump, which they will supply to you at no charge (no pun intended!). Just tell 'em DVM sent you.

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PostPosted: Thu Oct 27, 2022 7:43 am 
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Great, thanks!

I"ll keep you posted.


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PostPosted: Wed Nov 02, 2022 3:24 pm 
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So I received the new charge pump today and popped it in. The buzzing/crackly sound is still there. I took new voltage readings. They look better - there was definitely something wrong with the charge pump - but a few still don't look right. Here they are:

Leftmost IC
1. 4.75
2. 4.72
3. 3.70
4. 0.0
5. 4.69
6. 4.69
7. 4.70
8. 9.33

Center IC:
1. 4.70
2. 4.70
3. 4.69
4. -9.18
5. 4.69
6. 4.70
7. 4.70
8. 17.30

Rightmost IC (Boost):
1. 4.69
2. 4.69
3. 4.69
4. -9.17
5. 4.69
6. 4.69
7. 4.69
8. 17.28

Charge Pump
1. 9.31
2. 5.36
3. 0.0
4. -3.89
5. -9.16
6. 4.31
7. 5.83
8. 9.30

Sorry..this got more complicated. Any ideas? Thanks!


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PostPosted: Wed Nov 02, 2022 4:09 pm 
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All those voltages look great to me, well within normal variation. Don't worry about pins 6 & 7 on the charge pump--they're not connected to anything in the pedal circuit and the voltages can vary quite widely.

Sounds to me like the buzzy/crackly sound must originate elsewhere. If you haven't done a complete solder reflow, I would recommend that next--it solves an AMAZING number of mysterious pedal problems. Detailed guidance HERE.

Now that you have the charge pump issued resolved, you might want to try swapping TL072 positions around again and see if that affects the performance. Also try twiddling the pots and see if that makes the noisiness come and go.

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PostPosted: Mon Nov 07, 2022 6:57 pm 
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I reflowed all my solder joints, swapped the ICs, and fooled with the pots. No luck. Anywhere else to go from here? Perhaps a bad component? I do have a scope, but that would be a bit of a time investment.


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PostPosted: Tue Nov 08, 2022 12:02 pm 
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Was the replacement charge pump you received a 1054 or a 7660?

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PostPosted: Tue Nov 08, 2022 1:32 pm 
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Location: Groovy Beach, CA
bhenshaw wrote:
... On the drive side, however, I get this odd buzzing/distorted sound that appears as the notes are decaying. It happens more when the drive is pushed harder. I don't notice the sound at the first attack of a note, or if I play a note and mute it immediately. But when I let everything ring, amidst all the swirling and other sounds you'd expect, this weird buzzing/crackly/distorted sound appears, then cuts out before the "proper" sound completely decays.

FWIW... I recently built the regular SP (V 2.1) and compared it to my 2014 SP (V 1.0). There are some minor differences between the two circuits, and personally I prefer my older SP. I then attempted to mod the 2.1 to mostly resemble the old 1.0. After I reassembled the 2.1, the pedal began having what sounds like the same symptoms you are describing. In a nutshell: Both TL072 chips were faulty! Figured this out after replacing them with two new ones. The pedal seem to work fine before I went back in to mod it. I don't know what I could have done to cause those chips to fail.

Since I was already making a small order with Mouser for other projects, I took the opportunity to order a few (Texas Instruments) TL072CP's and a few (Microchip) TC1044SCPA voltage regulators. I haven't replaced the voltage regulator yet, but I will.


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PostPosted: Tue Nov 08, 2022 5:21 pm 
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byoc wrote:
Was the replacement charge pump you received a 1054 or a 7660?


TC 76605

I did have an extra TL072 which I swapped out for each of the OD IC's with no difference. I did not switch out both at the same time, so I suppose it's possible they're both bad - but seems unlikely.


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PostPosted: Thu Nov 17, 2022 1:36 pm 
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I switched out both IC's on the OD side with no difference. So to recap: we determined I had a faulty charge pump. After replacing the charge pump, the noise was still there. I reflowed all of my joints. I also fiddled with the pots to see if it was related to that. None of these things got rid of the sound I'm hearing. What is the most logical thing to do at this point? Thanks so much for your help thus far.


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PostPosted: Thu Nov 17, 2022 5:27 pm 
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Does switching to Ge clipping make any difference?

What brand TL072 are you using. Does it have a sort of bird printed on it, or does it have the state of Texas with an "i" in the middle of it? Which model? TL072CP? TL072IP? And what is the batch code?

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PostPosted: Fri Nov 18, 2022 5:34 pm 
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byoc wrote:
Does switching to Ge clipping make any difference?

What brand TL072 are you using. Does it have a sort of bird printed on it, or does it have the state of Texas with an "i" in the middle of it? Which model? TL072CP? TL072IP? And what is the batch code?



It's a Texas Instruments. TL072CP. Batch Code 18MDSHY.

These are the replacement IC's I purchased for myself. I'm getting the same noise that I got with the IC's I received in the kit.

I'm willing to take the time and money to rebuild the OD part of the circuit with new components, unless anyone has any better suggestions.


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PostPosted: Sun Nov 20, 2022 10:33 am 
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byoc wrote:
Does switching to Ge clipping make any difference?

What brand TL072 are you using. Does it have a sort of bird printed on it, or does it have the state of Texas with an "i" in the middle of it? Which model? TL072CP? TL072IP? And what is the batch code?


There is no difference between the 3 clipping modes.


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PostPosted: Mon Nov 21, 2022 12:27 pm 
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I'm sorry. I'm at a loss. You're voltages look good and I think we can assume that all your semi-conductors at good. I really don't like suggesting randomly rebuilding. If that's easier for you in terms of managing time/frustration, then I understand. Before you do that, one more question: Does it make a difference where the gain knob is set, i.e., do you still get the buzzing decay when the gain knob is full turn counter-clockwise?

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PostPosted: Tue Nov 22, 2022 3:06 pm 
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This part of the OP's pic is a bit fuzzy. And the red epoxy is reflective. The jumper wire between 4 & 9 looks a little "rough". I can't really tell if I'm seeing the effects of the reflection of the red epoxy, or stray bits of wire that might be coming in contact with output terminal 8?
Image


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PostPosted: Wed Nov 23, 2022 4:03 pm 
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byoc wrote:
I'm sorry. I'm at a loss. You're voltages look good and I think we can assume that all your semi-conductors at good. I really don't like suggesting randomly rebuilding. If that's easier for you in terms of managing time/frustration, then I understand. Before you do that, one more question: Does it make a difference where the gain knob is set, i.e., do you still get the buzzing decay when the gain knob is full turn counter-clockwise?


The amount of buzzing decay increases as I turn the gain up. At full conter-clockwise on the gain pot, I get a very small amount of buzz.


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PostPosted: Wed Nov 23, 2022 4:04 pm 
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syscokid wrote:
This part of the OP's pic is a bit fuzzy. And the red epoxy is reflective. The jumper wire between 4 & 9 looks a little "rough". I can't really tell if I'm seeing the effects of the reflection of the red epoxy, or stray bits of wire that might be coming in contact with output terminal 8?
Image


Agreed, it's rough - I had a hard time threading that wire through cleanly after everything was mounted. It's fine though - that was just a reflection.


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