Help With New Layout Glass Blower Booster Please

[sonolink]

Hello
I recently built 2 Glassblower Boosters and found a vero board layout by H.Sabro yesterday. I decided to give it a go and built it overnight. I introduced a couple of mods to implement a battery snap and power disconnection when input jack not present.

The pedal sounds great BUT, it seems to be always ON although the LED works correctly, meaning that it's boosting in both positions of the switch. I guess my mods are bypassing the switch or something similar but for whatever reason I can't see it. I'm using a DTDP switch btw.

I've attached original layout and layout with mods and some pics of the build.

Any ideas? Thanks a lot for your time and help.

 

[sonolink]

The mods:

 

[sonolink]

The original schem:

 

[sonolink]

My build

 

[sonolink]

The other side:

 

[sonolink]

Nobody?

Pleeeease.......

 

[midwayfair]

Measure with your multimeter whether your stomp switch's pole 2 is actually connecting to 9V in the off position. If all three poles are always connected to ground then start backtracking the mods until you figure out where the short to ground is.

 

[sonolink]

Hi Jon
Thanks for your reply

I measured voltages and in the off position  (when the LED is off) the middle contact on the switch (pole 2) reads 9.5v...

I can read this on the actual switch and on the vero board strip before r12.

Thanks for your help

 

[sonolink]

Any ideas? 

 

[midwayfair]

Any ideas? 

Did you backtrack the mods to verify that the switching worked without the battery-jack switching? That was one of my suggestions.

 

[sonolink]

I'm sorry I think I misunderstood you.

I understood that if all 3 poles read 0v THEN I should backtrack to see where the short is. Since there are 9v on SW2 I thought I had to go into a different direction.

Sorry for the language barrier

I will uninstall the mods then and make sure the original layout is ok and report back.

Thanks again for your help
Cheers
Sono

 

[midwayfair]

I'm sorry I think I misunderstood you.

I understood that if all 3 poles read 0v THEN I should backtrack to see where the short is. Since there are 9v on SW2 I thought I had to go into a different direction.

Sorry, I wrote the post on Mobile and some words were missing. You're right, it did sound like that's what I was saying!

 

[Michael Tibes]

I can't make sense out of what the transistors are doing here, maybe someone can give me a hint?

Michael

 

[midwayfair]

I can't make sense out of what the transistors are doing here, maybe someone can give me a hint?

Michael

Voltage controlled switch. This is pretty concise: http://www.allaboutcircuits.com/textbook/semiconductors/chpt-5/transistor-switch-jfet/

Basically it's how a Boss pedal works, but much simpler. Merlin seems to like using JFET-based switches, he used one in the Smalltime, too (though it had some problems there IIRC).

To be honest, Merlin could have made the footswitch short the op amp pins, which in my experience doesn't pop, since he was using a DPDT anyway. OP: You might want to just do that and rewire your footswitch.

 

[sonolink]

I'd love to try that but could you tell me what to do please?
I'm a beginner....

 

[midwayfair]

I'd love to try that but could you tell me what to do please?
I'm a beginner....

Sure. You need a DPDT if you aren't already using it.

Remove the JFET.

Connect the middle lug of your footswitch to the pad where the source was.

Connect the outside lug of that row of your switch to where the drain was. Not sure which outside lug to use? Put your multimeter in connectiveity (beep) mode. Press the switch so that the LED is on. Verify which lugs are connected together.

If your switch is:
1 4
2 5
3 6

And the LED is on when 2 and 3 are connected, you want to use 5 & 6 for the bypass.

Look up the datasheet of the JFET if you need the pinout to know which pads were the drain and source.

 

[sonolink]

Jon
Thanks a bunch for the indications

This will not change the transparent nature of the pedal, the 27dB gain or the fact it can be used as a buffer right?

The main reason I love this pedal is PRECISELY that it boosts without changing the sound

Cheers
Sono

 

[sonolink]

Sorry Jon but I don't understand what youre saying.

I removed Q3  (J112).
I connected switch pole 2 to where Q3 drain was connected  (c4/r6/IC pin2)

That seems clear. What I don't understand is the rest. After removing Q3 the LED doesn't work anymore but supposing it works when lugs 2 and 3 are connected what should I connect to 5 & 6. And where should pole 1 go? To ground?

Thanks for your help

 

[PRR]

> make sense out of what the transistors are doing here

sonolink really should include a link to the Project Page.

http://www.valvewizard.co.uk/glassblower.html

We have 9V supply on the pedal-board. With losses we get maybe 2Vrms out of an effect box. Some tube amp inputs make one overload sound with 2V in but a deeper overload sound with 4V(!) in.

Merlin ties the power rails to a buffered (transistors Q1 Q2) copy of the signal to *double* the maximum signal voltage "possible with one 9V supply".

(Transistor Q3 selects unity-gain or up to 20:1 gain; a verse/solo switch.)

You can ask why not a 18V or 47V supply? Or why not just turn-up the amp? Well, guitar-pedal is a funny world, and there is a niche for this.

 

[sonolink]

PRR

You're right. I apologise. A few days ago I posted about a problem I had with 2 pedals using Merlins layout and did put a link to the original circuit.

http://groupdiy.com/index.php?topic=61426.0

Then I found this vero layout and wanted to try it but forgot to mention the link...

According to what you say Q3 is then necessary to maintain the pedal original nature right?

I still can't figure out why it seems to be on all the time and Jones suggestion seemed an easy way out....

Any ideas?

cheers
Sono