EA Trem Slowdown ??

[petemoore]

After all the disussion recently about the EA TRemolo, I built one.
 Didn't take very long to get it tremmin'.  The LED pulses with the Trem waves...but very fast...the 100k makes some difference in the speed, but not that much, I think its up near top possible speed.
 I would like to get it slower. What's a good cap to start diddling with and values...I probably would like the speeds  to be in the 'medium' range..right now it's slowest speed is probably a little faster than "Too Much to Dream"...I'm getting my Strawberry Alarm Clocks Mixed up with my Electric Prunes...lol
 I presume it is one or more of the three seriesed .1uf caps above the 2n5088 that would tweek the speed...which one which way to hit the brakes???

[B Tremblay]

I presume it is one or more of the three seriesed .1uf caps above the 2n5088 that would tweek the speed...which one which way to hit the brakes???

Well, if that isn't a typo and you did use 0.1uF caps, that's the problem.  You need to replace all three with 1uF caps.

[petemoore]

Found the problem right away there ... Dohh...shouldn't be too hard to get em right...Thanks so much ...

[petemoore]

There was once a thread about flattening the EA Tremolo's oscillation to completely flat [that shouldn't be hard to do, getting it TO oscillate is usually the hard part of an Osc ckt]...anyway with the Oscillation completely stopped...it should be just like a Booster !!!
  Just one R change or add a cap could stop the oscillation and you'd have a sort of bypass switch ... ie the sound would still be boosted and you could have boost with or without trem with just an spst switch !!!
  What do you think??? someone's bound to have tried this ?

[B Tremblay]

The original design included the option of no tremolo effect, achieved by setting the Depth to minimum.  The original version uses a 1M Depth pot with a 560k resistor feeding it from the .47uF cap, and no resistor between lug 1 and ground.

I didn't need the boost feature and changed the Depth section components for a range that worked better for me.

In the RunoffGroove version, removing the 68k resistor should have the same effect, but it may be necessary to increase the value of the Depth pot and/or the series resistor attached to lug 3.

[p1_ind]

I think the original circuit just used an optional jack that you could hook to a footswitch to ground the gate of the jfet and thus grounding the oscillators pulse to the jfet so that it could be used as a booster.

Adam

[petemoore]

On the EA tremolo...I like it...get and don't need a DP or 3PDT !!!
 Obliiviously I'm going to try that !!!

[petemoore]

I replaced the caps above the 5088, but now there's NO tremolo efkt whatsoever !!!
 Everythings connected just like it was according to the DMM and the test clip wires I poked on there...just to see if there maybe a cold solder...
  I dunno...anyone have an idea what could have gone wrong?

[petemoore]

Maybe somehow I went past the sweet spot...I'm using a 2n7000 for the mosfetm a J201 and a 2n5088 for the transistors

[petemoore]

I didn't really want to start teaaring it up too bad, so I tried pulling Q3 [5088], it seemed at certain pot settings to modulat for about 1.5 cycles.
 Then I tried the small 1k range resistor over the uppermost cap of the three 1uf's and that pulsed the LED and signal however long it remained touching.
 It's like it wants to go again, but just can't quite get going. I tried different transistors in Q2 and Q3. Q1 seems to be biased in there just fine

[gez]

The amplitude of a phase-shift LFO's sine wave changes with frequency.  The way you had it set up before worked fine with the cap values you had, but now you have to recalibrate it to suit the proper values.

The thing to tweak is the resistance chain from the LFOs output cap to ground.  You need to get more of the LFOs output across the pot that sets the depth.  Try using a bigger pot.  The original used a 1M in series with a 560k resistor which could be changed to suit each individual FET.

Take a look at the original schematic, read through the accompanying notes and you'll get the idea.

http://topnet.com.au/~hairbear/page.2.htm

('guitar vibrato' article)

[Paul Marossy]

Pete-

What version did you build? The one from Nabke's site or GGG?

I built the one directly from Nabke's site, and didn't change anything. Used his PCB layout, too. It worked the first time with no problems, no matter how I have the controls set. I used the transistors that Aron said he used when he built his. (2N3904s and a J201, from the Schematics section of this site)

The circuit does have a lot of boost, but that is easily controlled by the level control.  

[petemoore]

Is what I'm trying to get going.
 I tried:
 1. changing the R value between the two 1uf caps and ground [xerok-15k-100k]
 2.changing R value ofthe 1k on the rate pot [zerok-15k]
 3.cutting the 470kresistor I had across the 500k depth pots outer lugs
bringing that from~250k range back to 500k range.
 4 adding R value to 68k resistor from depth pot to ground.
 5. different transistors J201's drain tpward pos. tried a few of these they boost signal slightly SGD now with the two bottom legs twisted and the Drain toward pos. letters facing output, just like in the boosters etc. [pretty sure they're  working in there.] Mosfet biases in nicely with the trimpot.
 Bout to build me a different one unless I've missed something I should try with this one.
 Starting with the EA Tremolo Modifications setup where from the schematic should I go with R values? Should I add resistors to the depth pot lugs?
 If I could get it to start oscillating I think I could find the values I want from there...

[gez]

Pete, I take it you're building the runoff version?  Are you doing the flashing LED mod?  If not do it, at least then you'll know whether the LFO is working!  

If the LED flashes and you're not getting tremolo then use a bigger pot for the depth control (1M) and tinker with the 120k to set the range.

If the LED isn't flashing, you're either missing a connection somewhere or the gain of Q3 isn't high enough to kick start oscillation.

Double check that the FET (edit Q2) pinout is correct and it's connected up ok.

[gez]

P.S. Measure Q3's collector voltage.  Maybe it's not biased correctly, or (if you've got it in there) the LED is the wrong way round?

[petemoore]

And even pulse about 1 second of pulsing, then nothing...[if the pots are set just right].
 It WAS Tremoloing...when I had the three .01uf's over the 5089, very fast oscillation...wanted to slow it down...put in the right caps [the three 1uf;s] then no osci...
 I'll try all the suggestions soon...got to get giggin' tonight though, and will probly be freid tomarry...lol ..I'll see what I can do !!  Thanks !!!

[p1_ind]

I am not sure because I used non polar 1uf caps, but you might check to see that you have the polarity correct if you are using electolytic 1uf caps.
Just a thought.

Adam

[petemoore]

I'm using a 2n5089's for testing in Q3 [tried a darlington too just for any possible 'kicks'].
 With a 2n5089 in Q3 these voltages were taken:
 Q3's       collector 3.12v //    base .6v   //   emitter 0.0v
 Should the collector of Q3 up nearer to 4.5v?

[gez]

I'm using a 2n5089's for testing in Q3 [tried a darlington too just for any possible 'kicks'].
 With a 2n5089 in Q3 these voltages were taken:
 Q3's       collector 3.12v //    base .6v   //   emitter 0.0v
 Should the collector of Q3 up nearer to 4.5v?

The 2n5089 should be fine and 3.12V on the collector should be ok.

Check the replacement caps - it worked before so maybe when you replaced them you caused a problem.  If you've shorted one of the caps then there won't be enough phase shifts to cause oscillation.  It's also possible one of the joints is dodgy.

[gez]

PS If all else fails try getting the bias more central, though I doubt this is the problem - according to the notes the sine's amplitude is around 2V peak to peak.