How do I wire a pcb to be always on?

[mth5044]

It's one of them first act delay pedals, and they have a pretty decent switch, but I want to have it always on so I can hook it up for true bypass in a largebox with some other effects. It looks like only one side of the switch is soldered onto the board, while the other just has its prongs sticking through the solder pads. Also, each solder lug on the switch has a trace going through the holes on the other side of the switch. So its kind of like this:

   ________
1|o - - - - o|4- - - - - to circuit
  |             |
2|o - - - - o|5- - - - - to circuit
  |             |
3|o- - - - -o|6- - - - - to circuit

where o's are lugs and - - - are traces. 1,2,3 are soldered to the board where 4,5,6 are just sticking into the holes. It also clicks when pushed down. Would I be correct in assuming that this would just be an DPDT but only one side of it being used? So essentially, I could just wire say pads 1 and 2 together (if 3 goes to ground or something) to keep it always on? Or could I even avoid having to take the whole thing off and just put a wire across 5 and 6 or whatever isnt going to ground?

Thanks for your help. If need be, I can take pictures of it, but there isnt really a way to see underneath it. Here is a link that shows some pictures of the circuit board. The switch is on the bottom left of the PCB in the first picture, but on the other side of the board.

http://pws.cablespeed.com/~danielzink/delay.html

[mth5044]

annnybody? I can only figure it is breaking the signal. I can't experiment until sunday when I get some copper braid to suck up the solder.

[.Mike]

I picked up one of these pedals last week. Nice for $30, especially after the buffer mod. I'm still pretty new at building and modding effects and am not entirely sure what I'm doing, but...

I've tried to trace out the circuit to this over the last week, mostly as a learning exercise. From what I've gathered, the switch is a momentary switch that applies voltage to pins 4 and 6 of the TC4013BP, which is a flipflop (Datasheet: http://www.datasheetcatalog.org/datasheet/toshiba/97.pdf). I believe that is what actually handles the switching.

I don't think it is as simple as just soldering a couple of the pins of the switch together to force the pedal to remain on, but I'm not sure.

Here are some closeups I took. The shot of the top of the board is flipped horizontally so you can overlay it right over the bottom of the board, and see where everything connects. The top is also two images assembled together to remove the header wires that run to the pots, which would obstruct the board in the photo. I've marked the pins H1-H10.



Maybe someone else can help you based on those pics.

Mike

[mth5044]

Wow you actually found one? I hear they are pretty tough to come by now-a-days. Not even toys-r-us has em anymore.

The buffer mod is great. I also did the self oscillation mod and longer delay time mod. Pretty good stuff for such a cheap pricetag.

Thanks for finding that info and posting it. I'm not to keen on IC switching, so hopefully someone else can offer some input.

[.Mike]

Yeah, my local Toys-R-Us had about 8 of them as of last week, about $32 with tax. They also had a couple dozen of the chorus pedal and a few distortions as well. The lady told me she thought they were going on clearance soon, so I'm going to be checking back. They're definitely fun to play around with.

Besides the buffer mod, I did the self-oscillation mod as well. I didn't have a pot, though, so I put resistors in parallel with the 36k resistor until I came up with a value I liked. I ended up with a 200k resistor in parallel with the 36k resistor to add up to 30.5k fixed. It's actually in that picture, although just crammed into place to test. That gives self-oscillation when the level is all the way up, and endless repeats when the delay pot is between 8 and 10. It works pretty good.

Good luck with the switching. I hope someone has a solution for you!

Mike

[served]

But you can try to connect  pin 2 to 1 or 3. one of them has to be the right one. Nothing cant go wrong, youll pass the circuit or switch it on.
Luck!

[.Mike]

So I was searching for some more mods to do on this pedal, and I came across a gem of a post by Mark Hammer over at a different forum: (Link). In it he suggests that the pedal likely uses a switching FET to bypass or blend the delayed signal in with the output. He mentioned a K30, and sure enough, this delay has a K30A.

I opened mine up, bypassed the effects, and jumpered the outside pins of the K30A (closest transistor to the input/output jack side of the board). Sure enough, the delay blended right in. So to answer your original question, this is all you have to do.

The LED, however, does not light-- it pulls its power off the output of the flipflop. But if you plan on wiring this up using a 3PDT switch, you can easily wire up an LED.

--------------------------------------

Totally different but related subject. You mentioned you did the buffer mod, presumably the one posted to another forum by Clay Jones. If this is the mod, you added either a 1K or a 2.2K resistor. It's the one that is tacked directly onto the resistor that is directly behind the output jack.

Assuming you used a 1K resistor like I did, you may or may not have noticed that just having the pedal in your signal chain creates a volume drop. I measured it by putting a signal through the pedal, and then plugging the pedal into my recording setup. I then plugged the signal straight into my recording setup, removing the pedal. The difference was about 4.25 dB.

Now, I'm still a beginner, but I'm pretty sure I've worked up a fix. I modeled the buffer part of the circuit, and started tinkering with a few values. I found that if you replace the 470 ohm resistor that is directly behind the output jack-- the one you tacked the other 1K resistor to-- with a 1K resistor, you significantly reduce the volume drop created just by having the pedal plugged in.

So, unsolder the tacked on end of the 1K resistor from the original buffer mod. Remove the 470 resistor that it was tacked to. Replace that resistor with a 1K resistor, and retack the first resistor back in place. Works like a charm, and brings the pedal nearly up to unity gain.

Here's an image showing my test results. The tones were .25 seconds each, frequencies corresponding with the strings of a guitar. The delay examples were set at min delay, max time, and level to unity. With the extra resistor change, the pedal is within 1 dB when in the chain compared to when it's out of the chain.



By the way, it appears as though a 1.1K or 1.2K resistor would makeup the last dB that is missing, bringing the pedal up to unity gain. I just didn't have a resistor to try.

I hope that helps someone!

[mth5044]

Wow thanks

I ended up putting aside the pedal and just building a delay from scratch, but now that you posted this I'm going to have to do something with it!

I didn't notice the volume drop you mentioned, probably because I never really played with it besides guitar>pedal>amp just to see what it could do. If I get around to putting it into something, I'll give this mod a whirl.

Thanks and good job on the mod!