Suggestions for a vintage tremelo pedal.

[petemoore]

I'm definitely interested in...Runoff Groove's done it again !!!
 Great read with the perf, schem, and text !!!
 Thanks Guys !!!
 Might take a minute or so for me to get to this one, got more than a few other's I'm waiting for parts for [SStone, Rosscomp, TB anda FF 'w/Steve's GE's]...Tremolo though...I really love just listening to a well placed tremolo cameo section, Strawberry Alarm Clock [Too much to Dream] all the way to Megadeath...love those trem parts !!!!

[V!N]

Perf and PCB layouts certainly come in handy. Do you use Adobe Illustrator ? I will build myself one of those perferted ones soon, with more speed and a blinkin' LED.

Here are some pics of my EA Tremolo on perf, my very first DIY effect ever ! All I knew in those days were GGG, Fuzzcentral and Steve.






As you can see, I ordered my perf form Bear Electronics (before they were small).






Spaghetti anyone ? Man, what a mess !






Voila, it still looks like this and always will be. I was very proud of it (still am) and am gonna keep this little relic just the way it is.

[B Tremblay]

Looks good, V!N.  Don't worry about the spaghetti, mine's just as bad.

Green = status, Red = rate

[petemoore]

Where have I seen those knobs on before?>??
 Dual Leds and one blinks??? in time with the LFO...too kool, and really even practical !!!

[Neutral]

OK, I've built my EA Trem and have an issue to iron out, maybe someone can help me.
I built mine according to the http://www.runoffgroove.com/eatremolo.html schematic:


I replaced the 250k depth pot with a 1m like the original schem and discarded the 68k to ground. I still have the 120k.
Also my Q3 is a 3n3904 as I couldn't source a 2n5088.
Everything else is the same.

I'm getting an amplified guitar sound but no effect (tremolo) at all.
The LED is on but doesn't flash.
Here are some voltage readings all taken from the negative rail:

Battery 8.9v

q1

d 4.9v
g 1.15v
s 3.1v

q2

d 0v
g 0v
s 0v

q3

b 3.57v
e 0v
c .63v

I've double checked all resistor values and transitor pin outs.

Any clues??

Thanks

[petemoore]

Q2 isn't doing anything, something must be miswired...
 Q1 the gate is higher than the source...I don't know what this ones supposed to be doing [amplifying?],  but I think the gate should be .7v higher than the source...looks suspicious...check Q2's surrounding wiring and connections, someone else may know more about Q1's status

[petemoore]

I think...there I go well I hink Q1's gate should be .7v higher than it's source...someone else may know more about it's status [what it's setup to do here] but looks suspicious at a glance...
 In the mean time check all the connections and wiring around Q2, as it can't be having all three [or even two] pins at 0v and operate under any conditions

[petemoore]

I guess I started page four...lol

[Neutral]

All the Q2 wiring seems right.
If I measure off the positive side of the battery I get aproximately 9v on each pin, except the gate which reads slightly less.
Q2 is a J201, is it possible it is dead? Are they easily fried? I soldered all the transistors very quickly but I did have a dead short on the board when I first powered it up due to a stray piece of copper wire :oops: so that might of upset it.
Is it possible to check transistors with a DMM?

[Bill_F]

Green = status, Red = rate

That's way to cool B! I've got to build it just to have the two leds! Would I be right in assuming the Red rate Led is the one shown on your perfboard layout. The Green  status LED is wired to the switch as usual?

[gez]

q1

d 4.9v
g 1.15v
s 3.1v

q2

d 0v
g 0v
s 0v

q3

b 3.57v
e 0v
c .63v

I've double checked all resistor values and transitor pin outs.

Any clues??

Thanks

I think you've confused the reading for the gate with the source for Q1.  The source should be around 1V, drain 4.5-5V and the Gate somewhere between 2-4.5V.  Assuming you've just confused the two, Q1 seems OK.  Just to be on the safe side though double check the pin out/connections etc.

Q3 is totally wrong! Have you confused the base with the collector?  The base should be around 0.6-0.7V not the collector!  You've either got the pin out wrong/connections wrong, or it's right, you've confused the base with the collector and the gain of the trannie you've used for Q3 is too low.  What are you using for Q3, have you subbed in something else?  If its gain isn't high enough the LFO won't oscillate - no tremolo!

[gez]

Also my Q3 is a 3n3904 as I couldn't source a 2n5088.

I think this is the problem.  Do you mean 2n3904? (never heard of 3n3904!).  If so, this trannie is unsuitable as it's normally used for switching and its hfe is pitiful...

[jimmy]

hmmmm im thinking about building this one, and i cant get 5088s, would a darlington work?

cheers
Jim

[B Tremblay]

That's way to cool B! I've got to build it just to have the two leds! Would I be right in assuming the Red rate Led is the one shown on your perfboard layout. The Green status LED is wired to the switch as usual?

Correct.  The green LED is the status indicator activated by the third pole of a 3PDT.  I actually have changed it to a yellow since that photo, as the green wasn't very bright.  It is pretty cool to have the pulsing LED in sync with the LFO.  A jumbo LED for the pulser would look great.

[B Tremblay]

hmmmm im thinking about building this one, and i cant get 5088s, would a darlington work?

I believe that Q3 simply needs to be a transistor with enough gain to oscillate and a darlington would definitely satisfy that condition.

MPSA18 should work, in addition to the usual high-gain NPN subs.

[Bill_F]

It is pretty cool to have the pulsing LED in sync with the LFO.

Thanks B. I've done that mod to my "small clone" and I love it. Not only does it have that coolness factor, but I find it so much easier to quickly adjust the chorus. It's nice to bend down, turn the knob and be able to guage the speed by the pulsing. Very helpful. As my son would say "It's well phat!"  :roll:

[gez]

hmmmm im thinking about building this one, and i cant get 5088s, would a darlington work?

cheers
Jim

The original used a BC108, can you still get those in Oz?  If not then any medium to high gain trannie should be alright.  Best thing is to breadboard it first.

If you use a Darlington you might need to tweak the 10k collector resistor to allow a reasonable swing at the output.  Measure the collector voltage and tweak if necessary.

[Neutral]

OK I'm back with some more accurate readings:



Q1 (BS170)

d 4.9v
g 3.1v
s 1.2v

Q2 (J201)
g 0v
s 0v
d 0v


Q3 (2n3904)

e 0v
b 0.6v
c 3.5v

The issue is I get a boost but no tremolo effect at all

Do you mean 2n3904?......this trannie is unsuitable as it's normally used for switching and its hfe is pitiful...

I have heard of other people using this one in an EA Tremolo. What transistors would be better suited here?
Could it have something to do with the resistor preceeding the Depth pot, as mentioned in this post:
http://www.diystompboxes.com/sboxforum/viewtopic.php?p=64317&highlight=2n3904+tremolo#64317

I am using a 1m Depth pot with a 120k resistor before it and the other side straight to ground.

What about Q2? Is this zero volt reading right?? Could I have a fried j201?

[B Tremblay]

Try a different J201 and you'll need a higher gain Q3.  2N5088 will work well.

Always socket transistors!  Saves a lot of headaches...

[ethniccheese]

Bill,

Where did you get the Small Stone pulsing LED mod?  I'm wanting to try this on my tremelo and my small stone clone phaser.  Is this a pretty easy mod done to anything with a pulsing LFO?