EA Trem from Tonepad debug help

[jkokura]

Hi Guys,

I've got something weird going on. I've built an EA trem from the tonepad layout. I have signal in bypass and signal when engaged. No mods, no substitutions, everything should work fine.

However, the speed pot is working backwards. It's wired according to the schematic and the layout, but the pot is working backwards. What's more, is when the speed get's turned down, and the trem gets faster, eventually it stops treming entirely. I'm going to go through it with my Audio Probe of course, but I was just wondering if anyone had an idea why it's doing this?

Jacob

[jkokura]

K so I flipped the pot around, and it works right now. I don't know why Tonepad's drawing is backwards, but I checked it against the schem and layout over at GGG and it seems JD's got that one the right way round. In any case, be forewarned if you're considering building the EA from Tonepad.

But I still have this interesting phenomenon happening where as you turn the speed up, at a certain point the circuit stops treming. After playing with the speed and depth pots for a while, eventually the trem comes back. I read somewhere about either lowering the pot value or that by replacing the 1uF NP caps with a lower value (.68/.47) You can change how the speed works. I think I'm going to compare the GGG improved EA which I've built and works just fine, and the Tonepad circuit and see if I can make this one work better at all. ANY suggestions helps.

Jacob

[jkokura]

Comparing the Schems of the IEA from GGG and the EA from Tonepad:

Differences:
- IEA has a built in input buffer using a Transistor, the EA from Tonepad simply uses a 2M2 resistor to ground. (I built the same buffer into my pedal before the Bypass switch, so this isn't my problem)
- IEA uses a different configuration for the Level Pot, a 4.7k with .47cap into a 25k pot, whereas the Tonepad circuit uses a 15k into a 1uF into a 10k pot. (I'm not having level issues, so this isn't my problem)
- IEA uses a 68k Resistor to go to ground from the depth pot, tonepad's has nothing. (Could this be the problem?)

There are a couple other minor differences, mostly having to do with value differences in parts that I think have something to do with compensating for the major changes JD added to his project. Overall, I kinda wish I had decided to use the GGG project from the beginning instead of saving some small amount on the fewer parts the Tonepad project uses.

Bleh. I think I'm going to play with the values of those three caps (1uF np), perhaps starting with .68uF and seeing if that clears up the issue. I might also recheck the values of the parts to make sure I didn't make a mistake somewhere. Still willing to hear ideas.

Jacob

[jkokura]

Changed those 1uF caps to .47uF caps, and I also added a pair of 68k resistors to the 100k pot. It changed the speed, and I got lots of usable settings out of the pedal. It's still doing the wierd thing where as the speed pot approaches max, all the trem disappears. I wonder if there's anything I can do to fix this, but at this late date, I think I may have to send this off as is. I thought about increasing the 1k resistor before the Speed pot, but I wasn't sure what that would do.

If anyone has an answer, I'd appreciate it.

Jacob

[Barcode80]

Check your JFET, swap a few out. I've found that JFETs (and JFET based opamps) vary greatly in their ability to sustain an LFO, so in some extreme cases stock parts values can cause some breakdown of the LFO. I've found this EXTENSIVELY with the NE5532 opamp for example, as most opamp LFOs I have built with it will not work when the original specified opamp was a 4558 or TL072.

[jkokura]

Great suggestion! The 2N5457 is what tonepad calls for, do you mean exchange the 2N5457 for something else? Or do you mean to try a different 2N5457?

Jacob

[Barcode80]

try a different 2n5457. JFET tolerances can be pretty wide.

[tasos]

hmmmm i am building this pedal...i have just produced the circuit board...i got great advice from here....i wanna make a question....is the led turning on and off with the tremolo signal?or just on\off with bypass?

[jkokura]

There are some modifications you can make to do what you're suggesting. Which Layout did you produce the board from? Tonepad? GGG?

Also, I changed out the 5457 twice, with two different batches. No change. I decided to leave it. I like character.

Jacob

[Govmnt_Lacky]

I have had a few "problems" with Tonepad builds in the past and the most frustrating part about it was that Francisco is virtually unreachable!! Even after purchasing boards from him there is no response from him when you attempt to contact him about his board builds. I read a while back that he was having health issues and that is truely a shame however, I also read that he was back to business as usual and there is still no contact.

[tasos]

ok i am not doing the led flasher!but what's going on with tonepad?i mean...great site but if more pedals tend be problematic at least  let people know~! :'(anyone who had a problem with a tonepad built please let me know!thanks...

[Barcode80]

Tonepad's projects are all built and tested before he posts them. No disrespect intended, but having built almost all the projects on there (including the EA tremolo), it is not FP's fault if you can't get it working...

[Govmnt_Lacky]

Tonepad's projects are all built and tested before he posts them. No disrespect intended, but having built almost all the projects on there (including the EA tremolo), it is not FP's fault if you can't get it working...

I agree however, I think that Fp should stand behind his boards as he says he will. When I built his GT2 and had problems with the board copper runs pulling up even with minimal heat I tried to contact him for 2 months! Finally, I just trashed his board and etched my own. That was THE LAST board I bought from there.
I believe I am in the minority of people who have bought boards from Francisco and had problems but it was the "customer service" that made me decide not to buy anymore.

[tasos]

hey!you are right!i might be the one who messed this up!i actually used regular pots!the only pots i can find....but you know this is the greatest thing about diy...making things  cheap with easily found parts in electtronic stores....anyway...at least this should be clearly pointed in the schematic.....

[Barcode80]

What do you mean "regular pots?"

Or are you being facetious?

[tasos]

http://www.mikroe.com/old/books/keu/01.htm  there is an image with some pots at the bottom of the link....i only can get the black one at my electronics store...and they can't tell me whether it is a taper audio or what else?yeah...so....this is a regural pot.....probably!

[Barcode80]

well, the taper of the pot shouldn't matter. 100K is 100K. the taper only affects the way in which the resistance increases from 0 to the value of the pot. If you can post some build pics or some voltages, we can probably figure out whats up.

[tasos]

if 2 people have the same problem it is not the diy'ers fault[probably...]tell me what voltages do you need?

[Barcode80]

if 2 people have the same problem it is not the diy'ers fault[probably...]tell me what voltages do you need?

So not true. No matter how many people have problems, if there are people that don't, then the layout and project are good. I suppose it is impossible for more than one DIYer to make a mistake, eh? 

[tasos]

yeah right...but many people had problems with tonepad and the govmnt lacky in this topic...find me another person who did that working wright!