# Soldado / Active EQ from PCB Guitar Mania



## joelorigo (Nov 29, 2021)

I finished the Soldado & Active EQ combo from PCB Guitar Mania. The Treble pot acts more like a volume control with a really loud spot in the rotation. The Level control gets louder then quieter then louder again as it is rotated clockwise. In the attached video I have the Presence & Volume trimmers on the EQ board backed off a bit from full. (The Character trimmer was omitted & jumpered, and the 2 LEDs omitted with an added 1M resistor for one, as I didn't want/need any extra gain, based on advice from the Facebook PCB Guitar Mania group.)


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## joelorigo (Dec 3, 2021)

Hi, just bumping this to the top


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## PJS (Dec 3, 2021)

What voltages do you have on your IC pins?


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## joelorigo (Dec 3, 2021)

Measuring IC pins is something I have never done. I am looking up how to do that now.


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## joelorigo (Dec 3, 2021)

I found an instructional video on YouTube. Here are the reading I get:
The 14 pin IC on the Soldado PCB:
1 4.72
2 4.71
3 2.98
4 9.34
5 2.42
6 4.69
7 4.69
8 4.68
9 4.69
10 2.91
11 0
12 3.49
13 4.69
14 4.69

Active Q PCB:
IC1
1 2.87
2 2.87
3 2.83
4 0
5 .82
6 1.36
7 1.44
8 9.56

IC2
1 1.44
2 .98
3 .97
4 0
5 4.95
6 5.01
7 5.01
8 9.56


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## PJS (Dec 4, 2021)

IC1 on the EQ board - what sort of voltage variation to you get with changes in the bass/mid/treble pots?


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## joelorigo (Dec 4, 2021)

The above measurements were with the pots at noon. 

Dropping them all the way down
1 2.86
2 2.86
3 2.83
4 0
5 .85
6 1.35
7 1.44
8 9.56

Turning them all the way up
1 3.25
2 3.25
3 3.20
4 0
5 .8
6 2.07
7 2.07
8 9.56


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## PJS (Dec 4, 2021)

I'm out.  That all looks about what I would expect.  The only other thing I would check would be to actually measure the resistance of the 2 pots that are behaving badly and check for smooth changes in resistance across the travel. They are both specified as linear pots, so you should get a nice linear increase in resistance as the pot is rotated


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## joelorigo (Dec 4, 2021)

Ok, thanks for your help! 

Am I measuring the 2 outer lugs of the pot? Pedal plugged in? Knobs up and down readings?


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## TGP39 (Dec 5, 2021)

The two outer lugs of the pot will always remain constant.  Say you are measuring a 100K linear pot.  The two outer lugs will always show approx 100kohm.  What you need to do is measure the wiper (middle lug) with lug 1.  At 20% rotation, it should measure approx 20kohm.  At 40% rotation approx 40kohm, etc. 
The pedal does not need to be plugged in.  

Steve.


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## TGP39 (Dec 5, 2021)

I took a look at the schematic over at the other website.  What made you omit the character trimmer?  You have the trimmer jumpered from pin 2 to pin 3, but the circuit leading to pin 1 is left hanging.  I believe this may be the source of your problems.  I would replace the green jumper with the appropriate trimmer in there and see if that fixes your issues.  Best of luck,

Steve.


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## joelorigo (Dec 5, 2021)

TGP39 said:


> I took a look at the schematic over at the other website.  What made you omit the character trimmer?  You have the trimmer jumpered from pin 2 to pin 3, but the circuit leading to pin 1 is left hanging.  I believe this may be the source of your problems.  I would replace the green jumper with the appropriate trimmer in there and see if that fixes your issues.  Best of luck,
> 
> Steve.


Thank you! Yes, I was advised by a post on the PCB Guitar Maina Facebook group by someone who paired the Soldado with the Active EQ that the LEDs didn't do anything and if I didn't need the additional clipping stage to omit the trimmer, jumper 2 & 3, omit the LEDs and add a high value resistor to LED1 or LED2. Currently there is a 1M in D1. Since I was going to first try the Soldado as a stand alone unit I thought I didn't need any extra clipping that the EQ circuit would add.

Anyway, I will pull the jumper and add the trimmer, but do you think I should also pull the resistor and put the LEDs in?


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## joelorigo (Dec 5, 2021)

TGP39 said:


> The two outer lugs of the pot will always remain constant.  Say you are measuring a 100K linear pot.  The two outer lugs will always show approx 100kohm.  What you need to do is measure the wiper (middle lug) with lug 1.  At 20% rotation, it should measure approx 20kohm.  At 40% rotation approx 40kohm, etc.
> The pedal does not need to be plugged in.
> 
> Steve.





PJS said:


> I'm out.  That all looks about what I would expect.  The only other thing I would check would be to actually measure the resistance of the 2 pots that are behaving badly and check for smooth changes in resistance across the travel. They are both specified as linear pots, so you should get a nice linear increase in resistance as the pot is rotated


The seem normal. Around 100 all the way up, around 50 at about 12 o'clock, and 0 all the way down.


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## TGP39 (Dec 5, 2021)

joelorigo said:


> Thank you! Yes, I was advised by a post on the PCB Guitar Maina Facebook group by someone who paired the Soldado with the Active EQ that the LEDs didn't do anything and if I didn't need the additional clipping stage to omit the trimmer, jumper 2 & 3, omit the LEDs and add a high value resistor to LED1 or LED2. Currently there is a 1M in D1. Since I was going to first try the Soldado as a stand alone unit I thought I didn't need any extra clipping that the EQ circuit would add.
> 
> Anyway, I will pull the jumper and add the trimmer, but do you think I should also pull the resistor and put the LEDs in?


Try installing the trimmer first.  Then go from there based on your results.


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## PJS (Dec 5, 2021)

If reconnecting the character circuit doesn't work then I am going to suggest disconnecting the EQ board completely, and focussing on one thing at a time. You seem to have problems on both boards (the level control you are talking about is on the preamp board yes?).  I am a bit surprised that they have specified a linear pot for this control - I would have expected to see an audio taper pot here.  Either way you shouldn't be getting a rise in volume then a drop.  A linear taper might give you a slow rise then a sudden jump though.  I wold expect audio taper to give a smoother rise through the pot travel.


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## joelorigo (Dec 5, 2021)

PJS said:


> If reconnecting the character circuit doesn't work then I am going to suggest disconnecting the EQ board completely, and focussing on one thing at a time. You seem to have problems on both boards (the level control you are talking about is on the preamp board yes?).  I am a bit surprised that they have specified a linear pot for this control - I would have expected to see an audio taper pot here.  Either way you shouldn't be getting a rise in volume then a drop.  A linear taper might give you a slow rise then a sudden jump though.  I wold expect audio taper to give a smoother rise through the pot travel.


OK, thank you! Yes each one of the pots in question are on a separate PCB.


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## joelorigo (Dec 6, 2021)

Pulling the jumper and adding the trimmer didn't change the issues with the 2 pots.


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## joelorigo (Dec 7, 2021)

PJS said:


> If reconnecting the character circuit doesn't work then I am going to suggest disconnecting the EQ board completely, and focussing on one thing at a time. You seem to have problems on both boards (the level control you are talking about is on the preamp board yes?).  I am a bit surprised that they have specified a linear pot for this control - I would have expected to see an audio taper pot here.  Either way you shouldn't be getting a rise in volume then a drop.  A linear taper might give you a slow rise then a sudden jump though.  I wold expect audio taper to give a smoother rise through the pot travel.


I guess I will take our suggestion and try them one at  time.

I have only followed a clearly laid out wiring diagram (BYOC Aion, PedalPBC. etc.), so just to confirm, this wiring looks good for the Soldado PCB, yes?


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## PJS (Dec 7, 2021)

That looks right to me


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## joelorigo (Dec 7, 2021)

PJS said:


> That looks right to me


Thank you


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## joelorigo (Nov 29, 2021)

I finished the Soldado & Active EQ combo from PCB Guitar Mania. The Treble pot acts more like a volume control with a really loud spot in the rotation. The Level control gets louder then quieter then louder again as it is rotated clockwise. In the attached video I have the Presence & Volume trimmers on the EQ board backed off a bit from full. (The Character trimmer was omitted & jumpered, and the 2 LEDs omitted with an added 1M resistor for one, as I didn't want/need any extra gain, based on advice from the Facebook PCB Guitar Mania group.)


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## joelorigo (Dec 8, 2021)

The Soldado by itself works fine!

So this is the wiring I am woking on for the EQ board by itself. There doesn't look like any thing on the PCB for the LED wire on the foot switch, right? No LED with the EQ only?


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## PJS (Dec 8, 2021)

That should work.  You could even wire it without the switch for testing - Just put the in/out jacks direct to the board


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## joelorigo (Dec 8, 2021)

Cool. Is this what that that would look like? It's just "on" as long as it's plugged in?


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## PJS (Dec 8, 2021)

Correct - as long as you plug in to the correct socket you will get sound at the other one, you just won't be able to bypass it, but that will also eliminate one potential source of error - the switch.


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## joelorigo (Dec 9, 2021)

I wired the EQ board as above and the pot still did the same thing. I removed the resistor from the diode/LED spot and put in 2 3mm LEDs. So now it's assembled per the build document. Now there is no sound going through.


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## PJS (Dec 9, 2021)

No sound at all?  OK, have you got an audio probe?  If so, then probe through the circuit until the sound disappears.  If not then look up how to make one.


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## joelorigo (Dec 10, 2021)

I’ll make an audio probe but I thought of something. In the above photo of the EQ board, is it possible that I have the LEDs in reversed? I have the negative lead in the square pad. I’m just trying to wrap my head around why signal passed through the circuit when there was a resistor in one of the spots but removing it and adding the LEDs there isn’t.


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## PJS (Dec 10, 2021)

The 2 LEDs go back to back, so if 1 is correct and the other the wrong way then that would affect it.  If both are installed the wrong way then that would be the same as installing them both the correct way.


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## joelorigo (Dec 10, 2021)

Someone on the PCB Guitar Mania Facebook group confirmed that I have them in correctly. Based on that they go back to back is it normal for the opposite LED light up when I use the DMM with black in positive lead and red on negative lead? Red on positive and black on negative lights up the one you're touching as expected.


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## PJS (Dec 10, 2021)

The anode of one LED joins to the cathode of the other, so that is exactly correct.  If you are using the multimeter in diode test mode then one LED will light up.  Reverse the leads and the other will light up.


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## joelorigo (Dec 10, 2021)

Thanks. Off to build an audio probe!!


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## joelorigo (Dec 14, 2021)

I'm back! After building an audio probe I discovered it is actually passing signal. Just very quietly depending on where the Treble pot is set. Which means it is still acting more like a "volume" control with that loud, scratch part as seen in the video in the original post. 

So to sum up, the Soldado Preamp works fine on it own (sounds good!), and the Active EQ is assembled per the original document, no more mods and the Treble pot is still wonky.


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## PJS (Dec 14, 2021)

OK, looking at the schematic, the treble pot would be a volume control if C2 was a short.  Have a look at the soldering around there - post a photo of the solder side of the board if you can.  Most likely is that the C2 end of the treble pot is shorted to ground somewhere.  You could probably check that with a multimeter.  If the soldering is all good then replacing C2 is probably the next thing to try.  If you have a capacitance meter you could test it first.


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## joelorigo (Dec 14, 2021)

Here is the photo. I don't have a capacitance meter, but how do I check with the multimeter for shorting to ground? From the schematic it looks like something to do with lug 1, right?


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## giovanni (Dec 14, 2021)

I would definitely clean those solder joints with alcohol and a toothbrush. Besides that, I don’t see suspicious joints.


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## PJS (Dec 14, 2021)

Yes, lug 1 of the treble pot.  It is hard to see on the photo of the component side, but looking at this solder side there is a lot of solder on lug 1 of that pot, and it is quite close to pin 4 (ground pin) of the op amp.  Check both sides and make sure there is no short there.  Maybe remove some of the excess solder.  To check for short to ground from the treble pot you will need the power disconnected.  If your multimeter has a continuity buzzer use that setting.  If not then use resistance measurement.  If your meter doesn't auto-range then choose the lowest range.  Put one probe on any ground connection.  Put the other probe on the pot lug.  If the continuity buzzer beeps, or if the resistance is zero or close to then you have a short to ground.


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## joelorigo (Dec 14, 2021)

There is no continuity witht one probe on ground and the other probe on lug 1. When you say check both sides and make sure there is no short you mean any solder from lug 1 touching pin 4 of the IC? There is none on either side. The big glob on lug one happened when I was removing the jumper or resistor earlier, so was not there initially when the pot had the issue. Here is a better photo of the top:


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## PJS (Dec 14, 2021)

Double check the value of C2.  It should read 4.7nF.  Most likely it will be marked either 4n7 or 472. Do you have a spare for C2?  Actually, just in case there is a broken trace, also check connectivity from Lug 1 Treble pot to C2, and from the other end of C2 to ground.  Use your multimeter the same way as before.


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## joelorigo (Dec 14, 2021)

The cap says 4700 100. Its a WIMA brand. I do have a spare 4.7n. There is continuity between treble pot lug 1 and one lead of C2 (the inner one) and continuity between ground and the other lead of C2 (the outer one).


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## PJS (Dec 15, 2021)

Actually, while you are at it, what values are C1 and C6?  They should be 10n, which I would normally expect to be the same size as the 4.7n.  It is surprising that they are so much larger.  Also, check the connection from Treble Lug 3 to C1, and also C1 to ground


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## joelorigo (Nov 29, 2021)

I finished the Soldado & Active EQ combo from PCB Guitar Mania. The Treble pot acts more like a volume control with a really loud spot in the rotation. The Level control gets louder then quieter then louder again as it is rotated clockwise. In the attached video I have the Presence & Volume trimmers on the EQ board backed off a bit from full. (The Character trimmer was omitted & jumpered, and the 2 LEDs omitted with an added 1M resistor for one, as I didn't want/need any extra gain, based on advice from the Facebook PCB Guitar Mania group.)


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## joelorigo (Dec 15, 2021)

C1 & C6 say 103K on them. 

I am getting continuity from one lead of C1 and lug 3, and continuity from the other lead of C1 and ground


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## PJS (Dec 15, 2021)

That all seems correct to me.  Should have asked you to check Lug 3 to ground as well.  The soldering looks really good though, so I doubt that is a problem.  The only other thing I would get you to check is the value of your 2.2k resistors (there's 6 of them).  In the photo they look as if they are 1.1 K (brown Brown Black Brown) instead of 2.2K (Red, red, black, brown).  I suspect that is probably just the lighting of the photograph though.  Resistor colours are bit hard to photograph well at times


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## giovanni (Dec 15, 2021)

Somebody more familiar with capacitor codes should be able to confirm, but I do believe the code 4700 means 4.7nF.


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## joelorigo (Dec 15, 2021)

The resistors do have red red black brown and all measure at about 2.2.

However I am NOT getting continuity between treble lug 3 and ground.


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## PJS (Dec 15, 2021)

That is all as it should be.  C1 is physically larger than the gap for it, so the leads will be sitting not quite where the board is deigned for them.  Just check and make sure they are not touching anything.  If I was troubleshooting this I would next replace C2 and see if that fixed it.  If not I would replace C1.


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## joelorigo (Dec 15, 2021)

Looking closely I can't see anything touching the leads for C1. I actually replaced it already because I had to pull the original to fit the trimmer.

As or replacing C2 I will do it but just curious about what you're thinking there. Sometimes there can be a bad cap? Should I try to reflow C1 & C2 first?


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## PJS (Dec 15, 2021)

You could reflow first.  The thing I am thinking is that the treble control really is (from what I can work out as a non-expert) C1, C2, and the treble pot.  You tested the pot ages ago and it seems to be working.  You have tested all the connections between the components.  The only thing left is the actual caps.  The character control may have some influence, but given that the symptoms haven't changed with those components there or not there I would assume it's not the issue here.  It would be unusual for these caps to be bad from new, but we are running out of options - unless someone else can see something I can't


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## joelorigo (Dec 16, 2021)

I reflowed C1 & C2. Didn't seem to make a difference. However, I'm not sure if this is different bu with all the trimmers and pots at about half way, there is no signal passing through. When I turn up the charakter pot the treble is acting like is has.  I'm going to replace C2 now.

EDIT: Replacing C2 didn't do anything


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## joelorigo (Dec 20, 2021)

I want to thank everyone of your help with this. The only thing I can think to add right now is that when it is plugged into a power supply one of the LED lights up, but not the both of them.


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## PJS (Dec 23, 2021)

The only thing I can think of is to post on the DIY stompboxes forum.  There are a lot of really good troubleshooters there.


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## joelorigo (Dec 23, 2021)

Thank you. Happy holidays!


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## joelorigo (Feb 9, 2022)

Update for anyone interested. After some awesome help form the DIY stompboxes forum, I can report that I have a Soldado with an EQ circuit. Not the PCB Guitar Mania Active EQ but the Tone TwEQ from Guitar PCB.


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