Equinox: Easy PT2399 Reverb

[sugonidamaso]

Thank you....

[mr_deadmaxxx]

Mine wasn't working.  Went over it with a magnifying glass looking for a bridge or crack.  Everything checked out AOK.  Tried sticking another diode in series with the 5v supply to drop things down a bit.  Didn't do it.  Then, going through this thread, I looked at the Russian site, and realized that there was supposed to be a switch.  For some reason, I thought the board represented the entire circuit and  I was all set to run the input and output pads to a stompswitch.  However, the Russian site drew my attention to the presence of a switch connected to the pads at the edge.  It should have been obvious to me, but somehow the schematic drawing threw me off.   So I wired up a switch and bingo-bango, I had reverb!

what switch is that?

[Mark Hammer]

what switch is that?

The switch that routes the junction of R22/R24 to either +9v or ground.  If you look at the schematic, it's way up in the right hand corner of the drawing. 

[mr_deadmaxxx]

The tails switch.

[Mark Hammer]

No.  the tails switch was working fine.  This is the bypass switch.  It applies V+ or grounds the base of the transistor it connects to, enabling or preventing the send to the delay path.  It doesn't "bypass" the effect, but simply cancels/disables it.  The signal passes through the input and output buffers at all times.

[mr_deadmaxxx]

What?!?

and here I thought that was the tails switch..so where's the tails switch?

[Mark Hammer]

It's over on the left side of the schematic.

[mr_deadmaxxx]

Isn't that the bass cut switch?

[merlinb]

Isn't that the bass cut switch?

Looks like there's some confusion! This is probably because I don't use true bypass switching- I think it's silly. I also like my delay effects to have tails. Hence this circuit has two switches.

1: Bass cut switch (it's just a toggle switch).
2: The footswitch. This controls the JFET on the PCB to give bypass with tails.

If you choose to use true bypassing instead, then you can eliminate the JFET and jumper it, or alternatively wire the gate control voltage permanently to 9V.

[mr_deadmaxxx]

I was right..

[Mark Hammer]

Note that the 10uf cap after the mix level pot can easily be dropped to a much smaller value. I dropped mine to 1uf, but it can probably be as low as .22uf or .1uf without much difficulty.  The smaller the value, the "brighter" the reverb will seem.  Just note that since most of the signal lives in the basement, raising the bass rolloff point via that cap will likely require you to also reduce the value of the mixing resistor (R5) to perhaps 3k9 or even 2k2).

Note that, since it comes with "tails", one could productively use a momentary stompswitch for the on-board switching.  That would let the user effectively "punch in" for a phrase, then punch out, letting the reverb decay in its own time.  That's actually a pretty dang useful trick for more straightforward delays too.

[merlinb]

Note that the 10uf cap after the mix level pot can easily be dropped to a much smaller value. I dropped mine to 1uf, but it can probably be as low as .22uf or .1uf without much difficulty.  The smaller the value, the "brighter" the reverb will seem. 

Isn't that what C33 is for? A bright sound?

[mr_deadmaxxx]

will a faulty PT2399 make the 78l05 heat up?
or a latch up make the 78l05 heat up?
i built this reverb and i get no reverb, just passing signal.and one of the symptoms is the 78l05 gettin really hot. also, when i engage the tails switch, i get passing signal (with no reverb) but when i disengage it, the passing signal is gone. not really sure what happened. I replaced 4.7k's with 4.6k's since i got them lying around..

thanks..

edit.

Yes I did see that. There's a bypass signal/tone now. After I remove the ground connected on my spdt footswitch. It also appears that the opamp measured 9.14v. I'll look for something else.

IT'S WORKING! It is the SWITCH(the foot switch from my wah-crybaby spdt)! How will I wire it? When I try to switch it off the whole effect shuts down-no bypass signal. Yes, the pot is the other way around.

something like this happens to my tails switch.disconnecting the ground from the spdt switch will fix the problem but still, no reverb.

[merlinb]

will a faulty PT2399 make the 78l05 heat up?
or a latch up make the 78l05 heat up?

Yes. (The 78L05 has internal thermal shutdown, so it shouldn't come to harm)

when i engage the tails switch, i get passing signal (with no reverb) but when i disengage it, the passing signal is gone.

Sounds like there is a short or something wired wrong around Q1. Did you sub a different transistor by any chance?

[mr_deadmaxxx]

will a faulty PT2399 make the 78l05 heat up?
or a latch up make the 78l05 heat up?

Yes. (The 78L05 has internal thermal shutdown, so it shouldn't come to harm)

when i engage the tails switch, i get passing signal (with no reverb) but when i disengage it, the passing signal is gone.

Sounds like there is a short or something wired wrong around Q1. Did you sub a different transistor by any chance?

Nope. No short whatsoever. Though disconnecting the ground or just leaving the middle lug of spdt switch unconnected to ground works just fine. Cant really tell why I get no reverb. Though some of the capacitors I used were used capacitors I just desoldered from another pcb project. Also I re-wired the 1N4001 diode in such a way that it acts as a fixed diode protection, so I get exact 9V at the DC power. Or an 8.4V really necessary to make this work?

Thanks..

[mr_deadmaxxx]

some photos, but still not working though..

[merlinb]

some photos, but still not working though..

I can't see anything wrong with the photos, except the missing switching transistor Q1. I don't know what to suggest; I mean, it's a PCB project. If you etch and stuff the PCB correctly then it has to work. If it doesn't work then there is a problem with the etch, or you've wired something up wrong, and you are the best person to check that. (Or possibly you have one of those dodgy PT2399s)

I assume the blue wire on the left goes to the pole of the footswitch?

[mr_deadmaxxx]

Yes. To the footswitch.
Must be the PT2399 as I see no other errors.

[waltk]

In your last photo, it looks like there's still toner all over your traces.  Is that just an artifact of the photography, or did you really just solder through the toner?

[alparent]

looks more like photo-resist