quick question: EA trem JFET substitues

[smoguzbenjamin]

Let's not start about Krauts then....

I've subbed every tranny I have. No banana. Time to use the last of my desoldering braid and remove the transistors from the keyboard amp I murdered a while back :twisted:

edit: I've just realised that the LED doesn't just become steady at any random point, but at the center between bright & dim. Hmmm. My brain's doing something, just don't know what yet :roll:

[smoguzbenjamin]

I just "darlingotnized" two 2n2222's in the LFO ckt. No difference, the LED's just a little brighter. I've also got an idea on what the LFO does, I'll draw it up in a sec and post it.

[smoguzbenjamin]

here's the drawing:

www.smoguzbenjamin.tk

Click on "EA trem LFO" in the menu bar.

From what I observed the LED does, this is what I think the LFO is doing. Is it for lack of Q3's gain?

[gez]

How long does the LED blink for before petering out, just once?

[smoguzbenjamin]

Once and it doesn't blink much at that. Sortof gets a bit brighter and dimmer and then back up to the halfway point... But it's really hard to notice, only the LED getting brighter is really obvious.

OT: how'd you like my silly 1 thru 10 animation? Also would you mind telling me what kind of popups you're getting? I used to get an "install porn now" sortof thing, and I asked the webmaster to remove that. I've disallowed cookies from my site (I don't use 'em), but everyone else might still get it. Did you get a porn toolbar? 'Cause if you did I have a few e-mails to send.

[gez]

If this is just happening after switch on then it's probably just the circuit settling in.  All I can say is go over ALL the connections in the feedback loop, i.e. the 1u caps and resistor legs hanging off them.  If you're 100% sure of them, then it's probably just the gain of the trannie not being high enough.

[idlefaction]

this also happens when you have not quite enough phase shift in your phase shift network, or your output load is too high - like when you have the speed knob turned up too far, or you have an open circuit in the tracks of one of the three filters in the feedback loop, or you have too low a resistance for the output.

if you've been trying this with the speed knob on 10 the whole time, turn it down a bit and see if that helps - you'll need to make the 'max speed' value a bit higher if that magically makes it go.

try it with the top lug of the depth pot disconnected - if that makes it go, maybe the pot or the 560k resistor are the wrong value.

if still no cigar, check all the PCB tracks around the LFO for hairline fractures, and all the solder joints for dry joints.

HTH...

[smoguzbenjamin]

Darren, I used the schematic from www.runoffgroove.com not GGG. I tried all pot settings, CCW, halfway and CW, no banana. Secondly my circuit is on a solderless breadboard and third, I'm going to re-breadboard the ckt to see if that magically solves the situation.

Anyway, it's not going to trem yet even if I get the LFO working, because I forgot that JFETs are voltage dependent semiconductors, and transistors are current-dependent. Tomorrow I'll have to go through the storm to get a 42 cent JFET. Damn :mrgreen: