SOLVED Paragon mystery issues

[giovanni]

I was very very excited to finish the Paragon since I heard very good things about it and every time is featured on TPS I find it really sweet sounding. To my disappointment, my build did not work at all.

Mods: I opted for channel 1 (right side looking at the pedal panel, red LED) high gain, channel 2 low gain. I omitted the charge pump and shorted the appropriate diode pins. I used 1N4148 and 1N914 instead of MA856 and 1S1588, respectively.

Here are the symptoms:
1. the right side (red) doesn't work at all, the pedal produces no sound if I engage it
2. the tone control on the left side works as a volume control - if it's all the way to zero, the sound disappears
3. the dip switches don't seem to affect the sound
4. if dip switch 2 is on (up) the left side becomes completely mute as well (which is weird because my assumption was that dip 2 corresponds to the other channel hard clipping)

All of the above make me conclude that I have some short somewhere, or maybe a bad IC or bad diodes or a combination of all of the above. I am at a loss. Before I start audio probing, I was hoping some eagle-eyed folks out here could point to the obvious flaw in my soldering or components.




I'll appreciate any help!

 

[Mcknib]

I don't see anything amiss everything looks correct

I wasn't actually expecting any incorrect values or polarity from a man of your ability thought I'd found a couple only to realise I was using the old build doc

Perhaps post your voltages that might highlight a problem area

I'd start by checking all the VREF points on the schematic

 

[giovanni]

Good point. I’ll try that when I get home on Wednesday (visiting the in laws). Thank you!

 

[jesuscrisp]

Something's probably up with the Vref, either component failure or some loose connection is my guess. Check the voltage divider resistors (R12 and R13) and C11. That would explain the issues with the tone knob and clipping. Does the other side of the clipping dip switch kill the tone too?

For the other side not working, check your connections between the switch board and the main board. Can't really see how you connected them from the pictures, but it could be a short at the solder terminals (if so more likely on the in-between sides that are not shown on the picture) or if you're using bare wire maybe something is touching there.

 

[giovanni]

The voltage divider is also used as reference at the op amp input, which is working fine, it seems. But I’ll double check the voltages. I used pin headers and the connections all look fine to me. I’ll do some voltage and continuity testing when I get back home. Thanks!

 

[giovanni]

I forgot to mention, the other side of the dip switch does not kill the sound...

 

[fig]

Gorgeous work sir.

 

[giovanni]

Gorgeous work sir.

Thank you! If only it worked!

 

[fig]

I've no doubt it will.

 

[Mcknib]

Meant to say the only thing I couldn't see was R20

 

[giovanni]

I just realized something. I tested the pedal with a 9V supply as I forgot I was supposed to test it at 18V. Could that cause the issues I’m experiencing? It doesn’t seem plausible to me but I thought I should ask.

 

[Mcknib]

I don't think it matters if you're getting correct bias voltages whatever you put in will be divided exactly in half but I've been wrong before

I once decided she was the girl for me Jaysus that was costly

Try it and see

 

[giovanni]

Yeah I also found threads where people discuss running it successfully at 9V…

 

[jesuscrisp]

No reason it shouldn't run on 9V since the original does too...

 

[MichaelW]

I run all of my Paragon variants at 9v. It just sounds better to me. But yah agree that testing with a 9v adaptor is not the issue. I'm watching this thread with interest because I have a non-working Paragon that I have not figured out why its not working sitting on the shelf. Waiting for me to get back to it when I feel like some self flagellation trying to figure it out. As I recall, I was losing signal with an audio probe right before Drive 1. I also have a Kliche that's not working right that I haven't figured out yet. It works fine except the clipping diodes do nothing. Not sure why. When faced with "Do you want to spend the next 3 hours troubleshooting or building something else?", I've so far chosen the blue pill and just moved onto a new project

 

[giovanni]

I’m gonna try and spend some time on this over the weekend. It’s been busy.

 

[giovanni]

Ok, after I pulled the pedal out of the enclosure and started testing it, some of the issues have gone away: both sides now sorta work and the tone knob no longer acts like volume. I’m guessing maybe there was something caught on the board (component lead?) that fell off once I pulled the pedal out. That’s the good news (is it good tho? I don’t like magical solutions…).

The bad news is that the clipping switches still don’t do anything. I tested one of the diodes from the same batch (got them from Tayda) and they seemed legit so I started trying manually connecting pin 2 of the IC to one of the hard clipping diodes and boom: crazy distortion. Unfortunately the debugging was interrupted by a sudden plumbing issue in the house that’s causing sewage water to drip from the ceiling, so I had to put a pin in it. Maybe I should start a troubleshooting thread for the plumbing issue…

Anyways at this point my guess is a bad dip switch. When I have time I’ll make sure that’s the case and will try replacing it.

 

[MichaelW]

Ok, after I pulled the pedal out of the enclosure and started testing it, some of the issues have gone away: both sides now sorta work and the tone knob no longer acts like volume. I’m guessing maybe there was something caught on the board (component lead?) that fell off once I pulled the pedal out. That’s the good news (is it good tho? I don’t like magical solutions…).

The bad news is that the clipping switches still don’t do anything. I tested one of the diodes from the same batch (got them from Tayda) and they seemed legit so I started trying manually connecting pin 2 of the IC to one of the hard clipping diodes and boom: crazy distortion. Unfortunately the debugging was interrupted by a sudden plumbing issue in the house that’s causing sewage water to drip from the ceiling, so I had to put a pin in it. Maybe I should start a troubleshooting thread for the plumbing issue…

Anyways at this point my guess is a bad dip switch. When I have time I’ll make sure that’s the case and will try replacing it.

Inspired by your tenacity (but not your plumbing issues) I took another look at my non-working Paragon and I think I found my problem. Somehow I must have handled the PCB a bit rough but there is a trace completely pulled up connecting the clippers. I thought it was a piece of fuzz and pulled on it......duh...made it a lot worse..I'm calling this one "done" and will be salvaging components off it.

 

[MichaelW]

you could just run a jumper between the components that connect and it would work

I tried that, didn't work, I pulled up about 1.5" of traces before realizing it wasn't a piece of lint I was yanking on.....I think I killed it.

 

[giovanni]

OK so I figured out why the tone knob was acting like volume: one of the legs was shorting against the LED bezel when tight in the enclosure. I also realized that the dip switch works perfectly fine, I just wasn’t able to take the time to carefully listen to the differences in sound, which are quite subtle in my opinion. I want to really make sure everything works correctly by rocking out a bit when I have a bit of time and then I’m gonna mark this as solved (yes, I’m superstitious!).

Thanks all for the help!