EA Trem---questions

rockgardenlove · May 11, 2006, 02:14:21 AM

So I breadboarded an EA Trem because I didn't have quite the right parts, and I wanted to see if it would still work.
It didn't work, and I'm fairly sure its breadboarded correctly...these are the parts I replaced:
180ohm-150 ohm
1.2k-1.3k
120k-130k
1uf-1uf(electrolytic polarized)
2.2m-2.7m
15k-12k

As you can see, I made quite a few part substitutions. Just for reference, here's the schmatic:

Are my parts at fault? I just want to know before I go and order a bunch more components.
I think I may have conceivably gotten the pinouts wrong though. For the J201 JFETthe source connects to the ground...is that right? I tried flipping the J201 both ways though, and it didn't work. How does the mosfet go in there? I'm a bit confused as I havn't used a mosfet circuit before...how does the symbol denote how you situate it in the circuit? I tried searching around, but couldn't find anything.

Thanks!

pyrop · May 11, 2006, 02:41:23 AM

With the flat side looking at you
left pin - drain - goes to 22uF cap
center pin - source - goes to ground
right pin - gate - goes to wiper on the depth pot

You should get still get sound without the J201 in place I think.
For the 1uF caps I have seen a schematic them polarized. The horizontal ones had the - on the right and the vertical one had the - on the bottom as viewed on the schematic.
Hope you get that!

pyrop

rockgardenlove · May 11, 2006, 03:45:11 AM

Alright, great man. Thanks.

Mind giving me the same info for the BS170?

I got some sound...it just didn't trembobulate at all. Parts issue, or my breadboard issue? What do you think?
(I'm leaning breadboard...mines too small so I have trouble cramming it all in.)

brett · May 11, 2006, 08:24:09 AM

Hi
BS170 is DGS with the flat side towards you. (2N7000 is SGD just to be confusing).

Does the LED pulse? I'm guessing not. Probably because it's best not to use polarised caps in such a circuit. Especially for the one that bridges the other two, as it has no polarising voltage on it. Try MKTs or greencaps.

cheers

B Tremblay · May 11, 2006, 08:48:45 AM

My guess is that the transistor orientation is wrong in at least one section. Those parts substitutions are probably minor enough that they wouldn't affect the circuit's operation.

Regarding the usage of polarized 1uF caps, I've had no problem with them in my two builds of this circuit.

rockgardenlove · May 11, 2006, 07:09:27 PM

Ok, cool. I'll try to find that PCB to try it.

markm · May 11, 2006, 08:08:06 PM

Quote from: B Tremblay on May 11, 2006, 08:48:45 AM

Regarding the usage of polarized 1uF caps, I've had no problem with them in my two builds of this circuit.

Same here.
No problems.

brett · May 11, 2006, 08:41:24 PM

QuoteRegarding the usage of polarized 1uF caps, I've had no problem with them in my two builds of this circuit.

There goes another theory! Live and learn. Hehehe

rockgardenlove · May 16, 2006, 02:24:04 AM

So on Q1 what does the drain, gate, and source connect to? I don't get the icon for Q1...thanks!

pyrop · May 16, 2006, 02:30:06 AM

Quote from: rockgardenlove on May 16, 2006, 02:24:04 AM
So on Q1 what does the drain, gate, and source connect to? I don't get the icon for Q1...thanks!

Drain to the 4K7 resistor
Gate to input
Source to 180R resistor

pyrop

rockgardenlove · May 16, 2006, 03:04:36 AM

But then the trimmer isn't connected to the drain, and so you can't tweak the drain voltage with the trimpot?

pyrop · May 16, 2006, 03:38:02 AM

Quote from: rockgardenlove on May 16, 2006, 03:04:36 AM
But then the trimmer isn't connected to the drain, and so you can't tweak the drain voltage with the trimpot?

That is right the drain voltage is tweaked through the trimpot which is connected to both the drain (via the 4K7), the gate (via the 1M) & to ground.
Think "Feedback" loop/resistor

pyrop

rockgardenlove · May 16, 2006, 03:46:58 AM

Well uh, its not changing anything at all.

pyrop · May 16, 2006, 03:54:31 AM

Quote from: rockgardenlove on May 16, 2006, 03:46:58 AM
Well uh, its not changing anything at all.

Do you have any voltage? & you are measuring the drain? (pin connected to 4K7 resistor)

pyrop

rockgardenlove · May 16, 2006, 04:37:48 AM

Yeah...uh.
I'm using a 50k trimmer atm...it should still fluctuate somewhat though. Battery at 9.3 volts, drain is steady at 2 or so volts.

pyrop · May 16, 2006, 04:46:48 AM

Quote from: rockgardenlove on May 16, 2006, 04:37:48 AM
Yeah...uh.
I'm using a 50k trimmer atm...it should still fluctuate somewhat though. Battery at 9.3 volts, drain is steady at 2 or so volts.

Needs to be a 100k trimmer or at least run a resistor in series with the trimmer ie 9v+ - 50k trimmer - 47k or 51k or 56k resistor - ground

pyrop

rockgardenlove · May 16, 2006, 05:37:54 AM

^Yeah, before that I tried using 33k fixed resistors before and after...

Its 2:37 AM and I'm multitasking. That's the problem. Tomorrow I'll wake up and find out I've made some incredibly obvious error

rockgardenlove · May 18, 2006, 09:51:47 PM

Ok, so I've gotten it to sound, no oscillation though. The LED lights, but doesn't blink.

pyrop · May 19, 2006, 03:07:48 AM

Quote from: rockgardenlove on May 18, 2006, 09:51:47 PM
Ok, so I've gotten it to sound, no oscillation though. The LED lights, but doesn't blink.

Double check the Q3 pinouts.

And from what Ive seen this is how you would place those polarized 1uF caps

pyrop

rockgardenlove · May 19, 2006, 09:13:34 PM

Fixed, I got a bad trimpot somehow.

Thanks though!

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EA Trem---questions