EA Tremolo Debugging

[azrael]

My buddy attempted a build of one, and it doesn't work 100% correctly (second build of his, first didn't work at all..). He insisted he do everything himself, but I don't think he really sat down to learn the basics of electronics and DIY pedal building. He's impatient like that...Needless to say, I think I'll be handling all our band's pedal building from now on, haha...and I'll have to debug this one. 

So it's an EA Tremolo, and I haven't gotten a chance to really look at it yet, and I need to familiarize myself with the circuit, but I wanted to see if anyone had an opinion on the problems...
Here's a quick summary:
- It's the GGG layout.
- The pedal turns on, and there's a tremolo effect, but it tends to fluctuate in speed. 
- He also wired it so the LED would blink at the same rate as the tremolo effect (One LED that serves as the TB indicator and rate speed indicator)...But it doesn't seem to do that at all. The LED blinks at a constant rate that's different from the tremolo effect's rate.
- Also, the tremolo effect disappears with the Carvin V3's distortion.

Here's what I know is either wrong, or may be a concern:
* From what I can recall from other EA Trem builds, doesn't the EA Tremolo have a trimpot? The GGG Layout doesn't have one. Which resistor needs to be a trimpot?
* Do the 2N5457's need to be matched in any way?
* Definitely a couple of cold solder joints. Don't think he could solder if his life depended on it.

[profgoop]

I have just built the EATremolo from GGG and am having problems as well.  I get a low, clean signal through the pedal but no tremolo.  I did check the voltages at the transistors and Q1 is slightly different.  The collector is getting the full voltage from the battery and the base and emitter are slightly higher.  I used multilayer ceramic caps with the same values, could this be the problem?  I also checked the pinout for the transistors and matched them with the schematic.

Thanks guys for the help!!

-The Gooch 

[Drake120]

Well, I'm no kind of specialist, but looking at the schem, base and emitter CAN'T have higher voltages than the collector. They should be smaller than collector's voltage, and there should be difference between them (about 0.6V). Probably you have two traces connected were they should not be, or any other kind of short. The layout doesn't seem to tight, though... If you have a meter tahat can do that, check the legs of Q1 for connectivity. I'm just saying it from my own experience (not worked with EAT, though), where base and collector of one transistor were connected and it stopped my unit from working...

Good luck with it! And wait till someone wiser will help you

(JD)^S

[profgoop]

Thanks for the help!

I actually had a 180k resistor where I needed a 180 ohm!!


makes a huge difference , the pedal now sounds awesome.

-The Gooch