Cerulean kit troubleshooting (Bluesbreaker/Morning Glory)

[antonis]

Check continuity between pot lug 1 & R2/R3/pin 6..
    //        //           //         //    2 & pin 7
    //        //           //         //    3 & C5 left leg..

If you're lucky, it will be an "open" connection somewhere around NFB loop, resulting into op-amp permanently hitting negative supply rail..

edit: posted right before PCB photos..
Plz also post items soldering side..

[Lenougat]

Checks done : all continuities you mentioned are ok.

Here's a pic of the other side, the gain pot is at the top left corner !

[antonis]

Here's a pic of the other side, the gain pot is at the top left corner !

Are you sure..??
('cause it's labeled as VOLUME on previous photos..)

[Lenougat]

Sorry about that 
You are right, it's on the right side on the last pic... 

[11-90-an]

I'm guessing that even with an audio probe there still would be no signal.. right?

Have you tried checking continuity between lug 1, 2, and 3 to ground?
Maybe a solder blob encroached on the ground plane somewhere...

[Lenougat]

I don't have an audio probe yet, never needed one so far... I think it will be my next build, soon 
Otherwise, I've got continuity between ground and leg 2, but not between ground and legs 1 and 3.

[antonis]

I've got continuity between ground and leg 2,

You shouldn't..

Take IC off socket and measure again lug 2 & GND continuity..

[Lenougat]

Ok, there was a misunderstanding between us : I've measured the continuity between ground and the gain pot legs : continuity only on leg 2, not on 1 and 3.
Concerning the IC, I've got continuity on lugs 4 and 7. Lug 4 is normal, but 7 ?
Searching further on that side, I've found that one leg of C2 is grounded too.

So if I'm looking at the schematic, I think there is a ground somewhere is that area that shouldn't be ?

[Lenougat]

Correction : I don't know why the measure was not correct previously : legs 1 AND 2 have continuity with the ground. Leg 3 doesn't.

R3 and R2 are showing connection to ground as well, on one leg each. Just to improve my knowledge : is it normal, given that there's a condensator between them and the ground ? I mean : to show continuity with the ground, does a component need a direct connection to it on the schematic, or can I assume that if it is mounted in serie with something grounded, it is normal to have one side having continuity with the ground ?

[Lenougat]

Well, I've found for the pot's legs 1 and 3 : when the pot is set all the way down, legs 1 and 2 are connected to ground, when set all the way up, legs 2 and 3 are connected to ground. Pretty normal. Except that leg 2 shouldn't be connected to ground, according to me (perhaps I'm wrong...)

[antonis]

Are we still talking about Gain (DRIVE) pot..??

Caus if that's so, NO pot leg should be connected to GND..

[Lenougat]

Yes, I'm talking about the drive pot. That's why I think there's a problem on that part somewhere. Leg 2 is always connected to ground, as well as the components directly linked to it.
I can't figure out what can cause it to be grounded. The soldering job is not professional, but quite clean anyway... And I didn't touch anything except that pot.

[antonis]

I shouldn't rate your soldering job quite clean, but let it be..



Dark blue PCB area between green lines is GROUND..
Use a desoldering pump to completely clean pot pads and solder them again only using a smear of solder..

P.S.
Before soldering a heavy item, like pots or switches, it's better to have its legs already tinned so it would not need neither prolonged heating nor excessive solder..

[11-90-an]

Or you can sand the pot legs slightly... whatever to make it quick to solder...

The ground plane must be the reason why your voltage readings are hovering close to 0...

[Lenougat]

Ok, I've removed the solder blobs with a pump. It's cleaner now. That's what caused the ground ! I didn't know that the ground what so close from the soldering patches...

There's something else now that I need to investigate : when I test the effect outside of the board, it works. When I box it, it doesn't work any more. The bypass works, the LED lights up, but there's no sound. When I unbox it, it works again... 

[antonis]

By "unboxing" do you mean completely out of enclosure without desolder anything (just unbolt items nuts)..??

If so, taking in mind working LED, probably OUT Jack Sleeve isn't grounded via enclosure, maybe due to its own Sleeve or  IN jack Sleeve not making contact to metal box..

[Lenougat]

The jacks were still attached to the box, but the boards were out, without desoldering anything.
I was wondering if something unexpected, when attached to the box, was making contact with the ground.

In fact, the output plug was slightly moving (not attached firmly enough), probably making (sometimes) contact between the hot leg and the enclosure. It was tightened during the first tests, and I've seen it moving slightly when trying to figure out what was making contact.

Good to know for the next projects : the corners of the enclosure -125B- don't let a lot of space (and the jack are on the top with the DC input, not on the sides of the box)... But personally, I prefer when all the connections are on the top side. It saves some space on the pedalboard...

Now it works correctly !
Again, many thanks to you guys ! It's frustrating to be so far away, so we can't share a beer, but who knows ? One day perhaps...

Ps : the mod makes this pedal very versatile, from a light and transparent overdrive, to a high-gain distortion. With the gain over 12 o'clock, it looses clearly its blues spirit, but remains on the dark side of rock n' roll ! Between 3 and 5 o'clock, there is a kind of "white hum" that can be annoying if playing on stage (that's not may case...).
But this versatility is what I was looking for. When on the move, I'm playing through a pocket amp alone, which has a crappy sound except for clean tones. Now, I'll add this pedal to my "travel rig"...!

[jackwithoneye]

R7 is supposed to be 1K, you have 1M installed.

Willienillie, you rock !! This swap solved all the problems immediately !


[/quote]

Damn! Thank you so much, i had the exact same mistake on the R7.
Now full range is available and the Volume and Gain combinations make instantly more sense 

[jackwithoneye]

I think i've been over-enthousiastic about my problem solving.
Everything was quite perfect when i tested the pedal by itself, but once on the pedalboard chain, something new appeared, probably a grounding issue. (I'm still learning about how electronic works, so i might be wrong on this too )
I've been building the morning glory version of the aion circuit

When i increase the drive knob up, it's killing the signal down.
When i measure the resistance beetween the ground and the JACK IN, it varies with the volume knob. (while the RPD calue is a 2M2 resistor)

My Pin 1 of the Volume is grounded as it should.
My pin 2 of the Volume knob is changing as i turn the knob, as it should.


IC removed:
pin1 4.07v
pin2 3.56v
pin3 4.35v
pin4  0v
pin5 2.2v
pin6 0v
pin7 0v
pin8 8.95v


IC in place:
pin1 4.41v
pin2 4.58v
pin3 4.35v
pin4  0v
pin5 2.2v
pin6 4.41v
pin7 4.41v
pin8 8.90v

thank you for your help guys

[11-90-an]

Can you check continuity of lug 3 of the drive pot to ground?