SOLVED Speedy Gonzalez no effect, just high pitched noise.

[andrewcx13]

Last of my current non-functional pile is 2 Speedy Gonzalez pedals. Bypass signal passes through, led lights up, but when the effect is engaged all I'm getting is white noise. I can change the pitch a bit by rotating the volume knob, but otherwise there is no passing of signal once the effect is engaged.

I had this wired up on my breadboard testing rig, so the wiring for the jacks, 9v and the footswitch are essentially omitted in these pictures. I have the 3pdt on a PedalPCB 3pdt breakout daughterboard so I'm sure the wiring is right.

Thank you for your help, just at a loss as to how to figure this out.

Pictures

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[Betty Wont]

If you are getting the same issue on multiple builds, I would suspect a wiring or component issue. Where did you get your 5457s? Are you sure of the footswitch used for testing? If you used a bad one for both...

 

[Mcknib]

Did you get your BC184s from Tayda if so they clump the 184C and 184Ls together and they aint the same, make sure they're not 184Ls with the weird ECB pinout

BC184 BC184L BC184LC General Purpose Transistor NPN

Fairchild - Get It Fast - Same Day Shipping

www.taydaelectronics.com

 

[andrewcx13]

So these are the transistors I was told were a suitable replacement as BC184's were scarce

MPSA18 Central Semiconductor - Transistor: NPN | bipolar; 45V; 0.2A; 0.625W; TO92; MPSA18-CEN | TME - Electronic components (WFS)

Central Semiconductor MPSA18 | Transistor: NPN; bipolar; 45V; 0.2A; 0.625W; TO92 - This product is available in Transfer Multisort Elektronik. Check out our wide range of products.

www.tme.eu

I have a feeling this is probably my issue.

from what I see on the data sheet, I think it may just be these are in backwards.

 

[giovanni]

Those look like they have the opposite pin out as the BC184 above. Try flipping them and see what happens.

 

[andrewcx13]

Flipped em on one. The effect is now there. There is a high pitched whining sound though that is present when the effect is on with no input. Is there anything in the circuit that I could have fried by hooking this up with three of those transistors in backwards?

 

[giovanni]

Nah I think they are fine. Does the squealing stop if you short the input?

 

[Mcknib]

Your C104 should be 330pf looks like its an nf value can't see the code clearly looks like 334 or 330nf they look to be connected between collector and base so might cause hf oscillation

Transistors will be fine put in backwards they just won't conduct as intended

 

[Chuck D. Bones]

I think McKnib found something! C104 definitely looks like 330nF. Check out C107, that one looks correct. C104 should be the same. 330nF there won't cause oscillation but will kill the gain of that stage.

You need to redo the visual inspection and see if anything else is amiss.

Q1 is facing the right way in the pic.

It's normal to get noise, hum and/or squealing if nothing is connected to the input.

 

[andrewcx13]

Ok, entirely right on C104. Swapped in the right value there on them both. I'm waiting on new BC184's from tayda as I ran out of my replacements and the ones I took out the other day did not come out in one piece sadly.

So the one that has the transistors in the right orientation now and the right capacitor in C104 works. The squealing is still there though. with the effect bypassed it is not.

 

[Chuck D. Bones]

Does it squeal when you plug your guitar into it?

 

[Mcknib]

330nF there won't cause oscillation but will kill the gain of that stage.

Damn! Knew I shoulda put an IDK in there, but I did put a might coz...

IDK

Thanks Chuck now IDoK

 

[andrewcx13]

It was squealing when I had nothing in the input and was using the audio probe to see if I could find the cause in the circuit. I'm not sure if that answers the question though

 

[andrewcx13]

re-cleaned the board on this, double checked cap values, and reflowed all solder joints. distortion sounds better, but that high pitched noise is still there. grounding out the input jack the squealing remains.

 

[Chuck D. Bones]

You have two boards on the Troubleshooting forum. I'm going to stand down on this one until we get the ADHD working because they may both have the same root cause.

 

[andrewcx13]

Yup, good call. My stupidity, which came to light in the ADHD thread, was that I borrowed my bassists power adapter thinking it was a normal one spot, and instead it was an 18v MXR power brick adapter. Fun times.

Hooked up my new variable dc power source and all of a sudden it works. Thank you all for your help