Need Help w/ Deadringer Problem

[Paul Marossy]

I'm not entirely sure it's really a problem but I am still going to ask.

I'm building one of these for a friend per the single sided layout HERE.

What seems to be a problem is that my "FCV" switch appears to not be wired correctly. The reason I think that is because the boost function only works on two of the three switch positions on the "FCV" switch. Two positions are obvious, but the other one I can not hear any boost whatsoever - not sure which position it is other than being one of the end throws - so down I get boost, middle I get boost and up I get no boost at all. The switch has to be a DPDT on-on-on switch (and it is) and functions like the picture shown here:



So is this normal for this pedal or is something wrong?

More importantly, ALL of the switches make a popping noise and the drive, boost and tone controls all sound like they have some DC on them depending on how the mos/sil & FCV switches are set.

Very annoying. I've already spent like five times as long as I should have trying to build this thing. I've double checked everything and wired it per the PDF file. So what the heck is going on?!?!

[nzCdog]

I built one recently for a friend using that layout... it's a rocking pedal.  After reading your post, I don't think there's anything particularly unusual from my experience with the circuit.  From memory the Boost stomp only makes a difference on 2 of the 3 settings... it's been a while, but I think the one that didn't change was the higher gain one, which would mean that was because everything was already saturated.  

More importantly, ALL of the switches make a popping noise and the drive, boost and tone controls all sound like they have some DC on them depending on how the mos/sil & FCV switches are set.

All the toggle switches and the boost stomp pop a little when operated, that's normal. The bypass switch is pretty quiet tho.  All the pots should have DC bias on them so I'm not sure what you mean by 'sounding like it'.

[Paul Marossy]

Yeah, it's the higher gain one that doesn't seem to boost. I figured that might be normal (I also discovered that how the drive control is set makes a difference - when it's down low you can hear a boost, but not when it's all the way up). But the noisey switching is not going to fly. Every switch makes a popping noise. If you watch a YouTube demo of the real deal, all the switches are very quiet. The one I'm working on is just not acceptable.

I'm not new at this, I've built literally hundreds of pedals and this is the first time I've run across anything like this - especially using a nice wiring diagram and all. I don't know how old the PCB was that he sent me, it looks pretty much like the one on the PDF file. He could have had for about a year now I think. Was there a mistake on the earliest boards or something?

EDIT: On the pots, scratchy noise when you turn them. Which control does it depends on which switch is in what position. Once again, on a YouTube demo video of the real thing you hear no scratchy noises when a control is adjusted. Makes me think there is a cap missing in the circuit somewhere...

[madbean]

There is DC on the pots by design so that is not the issue. The scratchiness most likely comes from a decoupler going faulty or something wrong with the Vb supply.

What kind of voltages are you reading on the IC, Vb, 9v, transistors, etc? That may help us track it down.

[Paul Marossy]

When I first "fired it up", it was completely dead. Measured voltages and found a problem with the bias supply - there was none. So I fixed that and now I don't see anything that looks like it is way off.

This circuit isn't that high gain... does it matter how long your wires are? He wanted me to put it into a 125 type enclosure, which forced me to use much longer wires than I would have liked and to put part of the circuitboard between the footswitches. I'm wondering if either of those conditions has anything to do with the popping switches. There appears to be a voltage spike whenever you use a switch that causes the pop. Weird...

EDIT: Forgot to mention that the LEDs being in or out of the circuit does not matter as far as the switch pop is concerned. I assume that the correct way to wire the LEDs is with the negative terminal to ground?

[Paul Marossy]

OK, so now I feel like an idiot. I finally plugged this thing into a tube amp last night and tried it - no popping from any of the switches. But if I plug it into my little LM386 test amplifier, pop city, ALL the switches pop - and that's what I had been testing it with previously. So at least I feel like my sanity has been somewhat restored on this one.

Thanks for the help anyway.  

[madbean]

That would have been the last on my guess list, but at least you got it going finally!

[Paul Marossy]

That would have been the last on my guess list, but at least you got it going finally!

I know, it never even crossed my mind!

[madbean]

I was working on an overdrive build today and had some terrible hum with it. I spent about 5 minutes checking over all my wires, testing rig and solder joints. Turns out it was the space heater I had on in the workshop. Turned it off, no hum. You just never know!

[Paul Marossy]

I was working on an overdrive build today and had some terrible hum with it. I spent about 5 minutes checking over all my wires, testing rig and solder joints. Turns out it was the space heater I had on in the workshop. Turned it off, no hum. You just never know!

Yeah, perfect example. 

[Paul Marossy]

Just for the record:

I finally got around to looking at this little audio amplifier to see if it had an input cap. It didn't. So I added one. Live and learn.

A little background on the LM386 amp tester thingie. It used to be a RadioShack mini-amp that I rehoused in a decommissioned enclosure. I guess my mistake was in thinking that it was OK as is. I found out yesterday that it didn't even have an input cap.

It was like this:


Now it is like this:

[nzCdog]

Well done!  And cool little amp
FTR  I hate electros for output caps, they have terrible DC leakage.  I think actually I changed the one on that deadringer to a 1uF film IIRC

[Paul Marossy]

Well done!  And cool little amp
FTR  I hate electros for output caps, they have terrible DC leakage.  I think actually I changed the one on that deadringer to a 1uF film IIRC

Thanks. It was OK with a tube amp, so all is well.