A modified layout for the old EHX Pulsar which is infamous for its LFO ticking bleedtrough. There is two mods that hopefully can solve it. First, an op amp input buffer and second the more common mod; separating the power with a small value resistor between the amplifier and the LFO section. LFO section also have its own power filter cap.
Verified, the LFO tick is minimal on my build. This is a really nice tremolo pedal!
ReplyDeleteThat's awesome. Glad the LFO mod worked. And it is the 500 verified layout.
DeleteCongratulations for your goal!
DeleteHello,
ReplyDeleteI built it, and there is not ticking at all :)
However, i am having little issues with it :
1- I think the Speed wiring is reversed with pins 1 & 3, unless you want the tremolo to go slower when turning clockwise.
2- The DEPTH pot is behaving strangely : full depth seem to be at 50%. When I go to the extremes, i have wet & dry signal mixed.
Checked the schematic and it matches the layout...and kizzer verified it so I'm fairly certain it is correct.
Deletehttps://effectpedalkits.com/wp-content/uploads/manuals/pulsar-tremolo-kit-building-manual.pdf
It is probably a short or a misplaced component somewhere?
I found the issue : the 10k resistor from DEPTH lug1-2 doesn't allow enough signal to go to ground. Putting a bridge instead of this resistor (or wiring lug 1-2 to ground directly) allows the DEPTH pot to behave as expected.
DeleteWhat does that 10K resistor do in the circuit?
Also, is there any way to add a RATE LED?
So, final conclusions, if it can be useful to any future builders :
ReplyDelete1- It is possible to add a RATE led. It involves the use of a 2N5088 transistor, but it's easy :
- Wire the positive lug of the led to line 6.
- add a 820R resistor to the led negative lug.
- wire the other lug of the 820R resistor to the Collector of a 2N5088 transistor.
- Wire a 220k resistor to the base of that transistor.
- Now wire the other lug of the 220k resistor to Q2's collector (right side of line P on the layout).
- Then, wire the emitter of that resistor to ground (right side of line R of the layout is fine for that).
and voilà :)
2- I do think the DEPTH pot is wired backwards. At least, it makes more sense to meto swap the wires to lug 1 & 3 (and make the bridge to lug 2-3 instead of 1-2). Maybe I did a mistake at firt try, or maybe the schematic was wrong?
3- Maybe there had a trace somewhere, but the depth pot was leaving some DRY signal bleeding. So, i wired the lug to the ground (instead of line I / 10k resistor), and now it works perfectly.
One again, a big thanks to you, FuzzHead, your layouts are much, much appreciated!
Great! Thanks for the info!
Delete