6 pulses now from "Mod EA'

[petemoore]

I've got it up now to a full 4 [six total but the last two the swing tapers off so about three seconds of pulsing activity] cycles of trm action going now on the Modified EA trem [2n7000, j201, and 5088]
 I tried a Darlingtransistor ]Q3] but the 5088 sustains the pulsing for about 1/4 second longer.
 Each cycle of LED pulsing/not pulsing is initialed by cutting and restoring power [unclipping the battery for a second er two].
 I figure it works as long as it's charging up the caps, then....[enter intelligent question]
 I'm about to goto smaller cap for one of the three 1ufs that form the backwardC shape to the right of the schematic as my initial mistake [that I changed to schem call] of using three .1uf's here made it work but at a very high rate.....but still I'm thinking there's another way around to get the LED's pulsing to sustain...any Ideas???   []
 I changed also to a 1 meg depth pot but didn't note any changes at the time...       ..[how that interacted with future ckt changes I can't say]
 Tried 13+v power, changing Jfets [mpf102 and alternate j201;s], poking a 4,7k resistor around here and there in the Q3 region...on any of the three 1uf caps this had a similar but lesser effect of causeing the pulses [but only like four].
 The speed pot works, I have it set for about two pulses per second.
 The LFO is almost over the wall...but keeps falling just this side of sustaining oscillation...
 The fact that it did work with the three smaller caps in the LFO section and that I've done serious checking continuity from bottom to top of board everywhere, double checked resistances/voltage, basically checking everything to be as sure as can be [almost...lol this is a ckt after all] that everythings right... :roll: which obviously it can't be...  :!:
 I appreciate all the help on the first couple times around the block on this one...maybe I'm getting closer and was able to offer a little more detail on this post...

[petemoore]

I almost forgot to ask the question:
 Which of the three 1uf caps in the LFO section would anyone recommend socketting first as a way to get [my] EA Modified's LED pulsing...
 I had three .1uf's in there from a misread, but it did pulse with my mistake mod/very too fast...aobve post more details it

[gez]

Hi Pete, this is turning into a bit of a saga!    I read that Bill F got this circuit up and running yesterday, so I don't think there's anything wrong with the tweaked values.

Two things spring to mind (but I'm clutching at straws really).  What type of caps are you using?  If you're using NP electrolytic the tolerance might be poor?  Also, try removing the LED and change the collector resistor to 15k as in the original - perhaps this will give you the extra bit of gain needed to kickstart this thing into life?

I'm away tomorrow for the best part of a week, so good luck at getting it going!

[gez]

Which of the three 1uf caps in the LFO section would anyone recommend socketting first as a way to get [my] EA Modified's LED pulsing...

Keep them the same but tweak the resistor legs would be my advice...

[Bill_F]

Hi Pete, this is turning into a bit of a saga!    I read that Bill F got this circuit up and running yesterday, so I don't think there's anything wrong with the tweaked values.

Yeah, the circuit works fine. I think it's a bit brighter than the one at GGG which I also built. I'm going by memory here and haven't AB'd them yet. I built this second one because I needed that flashing LED!  :lol:

The extra brightness is nice with Humbuckers, but maybe a bit to much for single coils. I still need to mess around with it some more. I may eventually mod it to switch in another cap (a fat boost) to make it more versatile for different types of pickups.

Bill

[gez]

The extra brightness is nice with Humbuckers, but maybe a bit to much for single coils

You can tame the high end a little by wiring a small value cap in parallel with the drain resistor (the 4k7).

[Bill_F]

You can tame the high end a little by wiring a small value cap in parallel with the drain resistor (the 4k7).

Thanks Gez. I'll give that a shot. Any suggestions as to what size?

Bill

[petemoore]

Kinda what I was figureing seeing how the cap change also defuctified it.
 I'm using 1uf 250v caps I got from RS, I'll try socketting these...and play with values...

[gez]

Thanks Gez. I'll give that a shot. Any suggestions as to what size?

Best thing is to clamp a couple of croc clips either side of the resistor and try different values till you get the right amount of cut for you (saves on solder/time).  Start with a 6n8?

[gez]

Actually, a better approach might be to wire up a REALLY small value cap between the drain and gate of Q1.  The problem with sticking a cap in parallel with the 4k7 is that the cut off frequency will be subject to change upon loading of the output.  In practice this probably won't make much/any difference, but still it's worth considering.

As far as values go I wouldn't have a clue, but I should imagine in the picofarad range (time to pull out those croc clips again!).