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PostPosted: Sun May 03, 2020 9:43 am 
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Hi, everyone! This is my first pedal build, but I'm a guitar tech, and have lots of soldering experience. I'm also a bit CDO (I have to spell it alphabetically), so I make my little processes when I'm doing things.

When I got my Brownface Harmonic Tremolo pedal, I went and downloaded the instructions before opening the package, and read them all. Then I opened the package and verified all the components were there, and laid them out in the order listed in the instructions (I even got an extra resistor).

As I soldered the components to the PCB, I checked each solder joint with a magnifying glass to make sure it was clean, then I snipped the ends off as close as possible.

The only spot where I had any trouble was on Step 2, with the four 220K resistors between the 154 and 683 caps. The solder holes are so close together I had trouble keeping the solder isolated. I have noticed, however, almost all the other pics of assembled and working PCB's have this same issue, so it may not be a problem, but I did try to clean it up and remove as much of the solder in that spot as possible (while still keeping an appropriate amount).

When I got the pedal fully assembled, I connected a new Duracell 9V (reads at 9.6V), and plugged into a Smokey amp I use for testing (also with a new Duracell) and a guitar. I left the pedal upside-down so I could adjust the trim pots according to the instructions (Step 7). The bypass switch and LED work as they're supposed to.

With the pedal (effect) bypassed, the signal comes through clean and strong, but when I turned on the pedal, the signal level dropped dramatically. Even as I adjusted the Level trim pot through its full range, the level was significantly lower than with the effect off. Also, it would intermittently mute as I adjusted the Level trim pot. The same thing happened when I adjusted the Depth Symmetry pot. When I finally started hearing the effect through the amp, I adjusted the Depth and Speed controls on the top of the pedal, and again, the output would randomly and intermittently mute. I haven't tried a power supply (because I don't have one), but it doesn't sound like a power issue to me.

It sounds like there's an intermittent grounding issue, but aside from adjusting the pots, there's no other movement, and I've already verified all the solder joints are clean and discrete. I'm at a loss.


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Brownface Tremolo assembled.jpg
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PostPosted: Sun May 03, 2020 9:52 am 
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Could you post a photo of the solder side of the PCB, please? Only the DC jack connections need to be unsoldered to lift the pedal "guts" out of the enclosure.

Intermittent problems are almost always due to a poor connection somewhere. Make sure the two ICs are fully seated in their respective sockets.

What type of solder did you use?

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PostPosted: Sun May 03, 2020 1:07 pm 
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Here's the other side of the PCB. The IC's are seated properly. I'm using Weller 60/40 rosin core solder, same thing I use for guitar repairs.


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Brownface Tremolo assembled back.jpg
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PostPosted: Sun May 03, 2020 6:00 pm 
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Those 220K resistor pads are that close together because they're already connected with a trace, so the joints being in contact doesn't matter.

An intermittent problem like you describe is nearly always caused by a weak solder connection somewhere. I would suggest working through this process: viewtopic.php?f=9&t=52188 I would include the connections to the DC and I/O jacks as part of that, since those solder joints look blobby and very irregular.

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PostPosted: Sun May 03, 2020 8:00 pm 
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I actually already redid the DC solder points. I decided to make the wires a little longer to allow for disassembly without desoldering. The I/O solder points are a bit blobby, but they just have a little excessive solder on them. I will redo them, though.

I went through the pics and looked closely at all the solder points (top and bottom), and didn't see any that looked bad. Some of the bits I snipped on the bottom of the PCB look (in the pics) like they're too long and sticking out, but it's just the camera angle. They're actually all less than 1/32".

I noticed near the bottom left on the bottom side of the PCB the green plastic is a little scratched/chipped. I know this is from the alligator clips on the "helping hands" I use, but could that be my culprit?

Thanks for the help! I'll let you know what happens.


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PostPosted: Mon May 04, 2020 3:39 am 
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The quality of your soldering is pretty poor. Look below the speed pot on the solder side of the PCB. Below it I see many poor solder joints. Many of them you can still see the solder pad. A quality solder joint will cover the entire solder pad. You should not be able to see the pad or down into the thru hole that the component lead goes thru. The Collector of the nearby 2N3904 for example. The soldering of the Emitter and Base looks bad too. All of the component leads striking thru the solder joint need to all be cut off at the very top of the solder joint. Do NOT leave any of the lead sticking thru any of the solder joints.

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PostPosted: Mon May 04, 2020 9:44 am 
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I have to agree with Stephen's assessment. What may be perfectly adequate solder technique on a guitar with handful of connections is likely to cause issues in a pedal with well over 150 of them. Each component connection joint on the PCB should be conical in shape, smooth & shiny, and completely fill the solder pad. And while most of your joints meet these criteria, there are many that do not. I would suggest going back through the build focusing on those joints that don't look as I have described and reflow & add solder as needed.

Here's a good informational post from Stephen: viewtopic.php?f=9&t=52211

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PostPosted: Mon May 04, 2020 9:48 am 
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I'll echo what Stephen (EDIT: and DVM) said. Understand you have a lot of soldering experience, but something is happening in this situation that is causing the solder joints to come out poorly. Perhaps these little pcb joints are not quite the same as the joints needed for soldering to guitar components.

Here are some additional resources.

http://www.byocelectronics.com/board/viewtopic.php?f=9&t=52211

Image

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PostPosted: Mon May 04, 2020 3:27 pm 
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Yeah, like I said, this is my first PCB project, and I have learned what's perfectly fine on guitars doesn't work on things 1/4 the size. LOL!

I went back through all the solder points and cleaned up a few that weren't pretty, and added solder to the ones that looked light. I tried again to snip off more of the leads, but my snips won't get any closer. They look a lot bigger in the pics than they really are. I also carefully removed both IC's, inspected them and the sockets, then reseated them.

However, I'm still getting the same problem. While it is a bit of an intermittent issue, maybe I'm not describing it properly. The level is very low when sound does come through, and it's very distorted and sounds like it's going through a compressor with a hard roof. I made a recording so you can hear exactly what I'm talking about. I tried attaching it here, but couldn't, so here's a link.

https://soundcloud.com/tito-jimenez-3/new-recording-17


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PostPosted: Mon May 04, 2020 4:32 pm 
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You've got a problem with either the LFO (low frequency oscillator) portion of your circuit or with the LFO phase inverter. Are you certain you have the 2N5089 transistor in the correct spot. Does the LED blink on and off?

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PostPosted: Mon May 04, 2020 4:42 pm 
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Yes, Keith, I reverified the 5089 is in the correct location and position. Sorry the pic is enormous!


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Brownface Tremolo assembled 3 5089.jpg
Brownface Tremolo assembled 3 5089.jpg [ 800.19 KiB | Viewed 2707 times ]
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PostPosted: Mon May 04, 2020 6:30 pm 
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And yes, the LED works as it's supposed to.


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PostPosted: Tue May 05, 2020 12:08 pm 
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So how do I troubleshoot the LFO and phase inverter? Do I do that visually? Do I use a multimeter?


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PostPosted: Wed May 06, 2020 12:21 pm 
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MojaveJohnson wrote:
So how do I troubleshoot the LFO and phase inverter? Do I do that visually? Do I use a multimeter?



If the LED is blinking and you can adjust the rate with the speed knob, then the LFO is probably working as it should. Please take voltage readings of the 4558 op amp and post the results.

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PostPosted: Wed May 06, 2020 1:36 pm 
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byoc wrote:
....Please take voltage readings of the 4558 op amp and post the results.

If you need details on how to do this:

To measure the DC voltage level on the op amp pins, 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. Report your results here. See the left side of the image below for the numbering of the pins.

Image

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PostPosted: Wed May 06, 2020 4:35 pm 
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OK, I've got continuity on pins 1, 4, 8, & 7.

DCV is:
1 - 6.59
2 - 4.42
3 - 4.36
4 - 0
8 - 8.83
7 - 2.25
6 - 4.40
5 - 4.35


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PostPosted: Wed May 06, 2020 8:38 pm 
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Pin 8 is your power source voltage, pin 4 is ground, and the rest should all measure right about 1/2 of the power source, i.e. ~4.5V. So pin 1 is high, pin 7 is low, and the rest look good.

Please take the op amp out of the socket and repeat the measurements on the socket pins.

EDIT: Voltages stated above are NOT correct for the Brownface Trem circuit. See my next post following for correction.

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PostPosted: Thu May 07, 2020 7:23 am 
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DCV on the socket pins (4885D removed):

1 - 11.11
2 - 11.06
3 - 4.37
4 - 0
5 - 4.36
6 - 10.80
7 - 11.01
8 - 8.81


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PostPosted: Thu May 07, 2020 9:54 am 
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My apologies on the voltages I quoted in my last post. While those values are typical for most op amp pedal applications, they are NOT correct for the Brownface Trem. The values you reported are right about exactly where they should be for this pedal. I'm a little concerned that your battery is running down, since you should be seeing over 9V on pin 8. You might want to try running through the trimpot setting sequence at the bottom of page 12 with a fresh battery, or better yet, a 9V center-negative DC power supply.

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PostPosted: Thu May 07, 2020 10:39 am 
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Your LFO appears to be working and your voltages suggest that the phase splitter is working. From your clip, it sounds like you're only getting one half of the panning. The next logical assumption is that you have a cold solder joint somewhere in the path between VR2a - Q5 or between VR2b and Q6.

Take voltage readings at the gates of Q2 and Q3. It will be the eyelet labelled "G". They are the two transistors in the lower right hand corner of the PCB. You should see a voltage that fluctuates in time with the blinking of the LED.

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PostPosted: Thu May 07, 2020 12:09 pm 
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duhvoodooman - I don't have an AC adapter, but the battery I'm using is brand new, and still reads 9.23V. And I already redid all the solder points.

Keith - Measuring the "G" eyelet on the two 5458 transistors I get 2.23-2.34 for the one next to the edge of the PCB, and 1.72-1.84 for the one next to it.


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PostPosted: Thu May 07, 2020 1:40 pm 
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Those voltages are lower and much closer together than I see on mine. With the Speed at the lowest setting (which makes it easier to read the fluctuating multimeter) and the Depth up all the way, I see ~2.5 - 3.6V on the gate of the outer 5458 and ~2.1 - 2.8V on the inner one.

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PostPosted: Thu May 07, 2020 1:56 pm 
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What DC voltage are you seeing at the bottom of the two 4.7K resistors located at the bottom right of the PCB? See image below.

Attachment:
BFT_R11_R12.gif
BFT_R11_R12.gif [ 171.31 KiB | Viewed 2587 times ]

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PostPosted: Thu May 07, 2020 2:49 pm 
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duhvoodooman wrote:
What DC voltage are you seeing at the bottom of the two 4.7K resistors located at the bottom right of the PCB? See image below.

Attachment:
BFT_R11_R12.gif



Using your image with the arrows as orientation reference, 21.6 for both at the bottom. From the top of those resistors, I'm getting 3.77 for the one on the outside, and 4.05-4.20 for the one on the inside.

And I've been doing all these measurements with the speed at minimum and the depth at max.


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PostPosted: Thu May 07, 2020 3:38 pm 
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The one on the inside looks good, but the voltage at the top of the outside one is very low. I see 10.8V on mine there (this is with the pedal in bypass). Try adjusting the Depth Symmetry trimpot until you get somewhere in the 10 - 11V range there and see how the pedal behaves then.

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