EA Trem report- not good

[Axmanjr]

:cry:   It's not working!!!  When I activate the effect- I get a boost.  So I can adjust the volume knob.  But the tremolo part won't work!  I get nothing from the depth and speed pots.  As a matter of fact, if I pull out a certain part of those pots from the board- I still get the boost.  By the way, I'm breadboarding it.  

Here's the schematic that I used http://www.generalguitargadgets.com/v2/diagrams/eatrem2_sc.gif

I also used this as a cross reference http://www.generalguitargadgets.com/v2/diagrams/eatrem2_lo.gif

Okay- some of the things that I did change (in which I was told that it was okay to do): 2N5088 to a NTE458, J201 to a MPF102, 50K log pots with 51K resistors inserted (to drop the value to about 25K).  I also couldn't find a 560K resistot- so I placed a 510K and a 51K resistor in series.  I also had a hard time finding 0.05uF caps.  So I placed two 0.1uF caps in series.

Any help is appreciated!

[RDV]

.047 will work fine in the place of .05

Regards

RDV

[Boofhead]

The fact you get boost means the transistor stage is probably working.  The most likely causes are wiring problem, JFET pin out-problem or your oscillator isn't oscillating.  

If you set the speed pot to slow then measure the *DC* voltage on the collector of the oscillator transistor you might possibly see a slightly erratic reading on your multimeter *if* the oscillator is working - if it's dead stable then it's probably not.

[Travis]

If you used those .1 uF caps in your osc then it is oscillating 10 times too fast.  The trem effect will be so fast it's inaudible, and the effect will be just that of a boost.  This seems to be the most common mistake made with the EA Trem.

"2N5088 to a NTE458" The NTE 458 is an N-channel JFET, right?  How would that provide the drive necessary to run the oscillator?  I was under the impression that Q3 had to be very high gain.  You might try subbing in a high hfe transistor.  Pretty much anything over 400 should do.  The pinout will be different.

The J201 and MPF102 have the same pinouts; flat part up, pins pointing toward you: DSG.

Good luck, it's a nice little circuit.

[Axmanjr]

Thanks for your replies.  I'll look into it.  

What is a high hfe transistor?  Also, what do you recommend me changing the .1 uf caps to?

[smoguzbenjamin]

Hfe is an indicator of a transistor's gain. A higher Hfe means a higher gain

[Paul Perry (Frostwave)]

If you used those .1 uF caps in your osc then it is oscillating 10 times too fast.  The trem effect will be so fast it's inaudible, and the effect will be just that of a boost.  

I think a X10 lfo would be MORE audible! (but, sound weird). I think the likeliest thing is no LFO at all, probably pinout confusion.
I have a trem on the bench at the moment running at 200Hz, and you can hear it OK!! at least, you can sure tell it is turned on. Not useful, tho.

[smoguzbenjamin]

I tried 0.1uF caps. The trem was just too fast... Using 0.68uF caps sounded pretty sweet though, but at max speed it sounded like no trem to me...