logitech precision pcb problem


I’m very new to stick building and I’m planing to do my first one using a logitech precision gamepad’s pcb.

Before ordering anything, I opened up my pad and tried to identify all signals and grounds with the help of this diagram :

Everything is working fine except for the down button. I tried first with my poking thingy but everytime I touch the orange common spot the left direction is inputed :

The other end of my cable don’t touch anything but the left command is on. I’m absolutely sure I didn’t touch anything else than the orange common pin.

I tried with a regular wire and it works fine. Orange signal linked to orange common input down command. I’m guessing it has something to do with my cables resistivity.

I’m worried to use this pcb while I don’t have any idea what’s going on with this down command. I did a research on this forum and found someone with the exact same problem. Unfortunately his problem seems to be unresolved.

Is there any electronics guru around there who can enlight me with his knowledge?

I’m assuming you have a cheap multimeter – if that’s the case then the problem is probably the meter’s internal electronics perturbing the signal line enough to make the Precision think that down is being pressed.

I’ve got a torn-apart Precision lying around that I’ve messed with a variety of ways and haven’t had a problem with L or D misfiring despite quite a bit of abuse. It should be okay if you wire it up correctly.

I didn’t even use a multimeter. The pad is connected to a computer and I’m trying to input commands by connecting two points with a cable.

With a cable alone it’s working but when I plug two stick like the one in the picture one to another and try to emit the down command the left one fires as soon as I touch the orange common.

I’m afraid to use this pcb for my stick with this kind of random effect. And by random I mean I don’t understand what’s happening at all.

No offense but are you sure you’re not accidentally shorting anything else on the board while you’re doing this probing? (It’s a pretty PITA board)
So what is that probe attached to?
Is it just two probes with a copper wire between them?
Are you touching the exposed probe?
How long is the probe cable?

I’m 100% sure I didn’t touch anything else than the orange common. The other end stayed in my hand not touching anything (not even myself).

It’s 2 multimeter’s probes with a wire between them. The probe’s connectors can’t attach one to another. Here what it’s look like:


It’s quite long. About 3.3m (10.8 feet) long.

For the record. this pad works on ps3!

Can some one please post a good tutorial on where to solder on this pcb?

This is going to sound really BS but please stick with me on it:
First, is this behavior consistent? Whenever you touch the DOWN signal pin does it fire off a LEFT?

Assuming this is consistent (or consistent enough):

Second, can disconnect your massive wire connection so you have one shortest wire probe and can you try to replicate the issue with the single probe? Is it more or less consistent?

Now, here’s the part that’s going to seem very BS-ish:

Try moving the offhand probe around, specifically higher and lower than the probe touching the signal pin – does this change anything?

My guess is that it’s possible that your probe-string is long enough that you’re getting a slight voltage differential that’s sufficient to upset the signal pin or you’re receiving RF interference on the long wire (as if it were an antenna). If this is the case then you shouldn’t have a problem with the pad once hacked together since you’re unlikely to create as large a differential (or antenna) as you’re getting now.

Either way, I think I’m going to try to repeat this experiment when I get home!

Some more testing.
Every time I use the red probe I have some left commands. Black probe or wire only don’t fire a single left. Black probe and wire input left but not stable. With the three of them connected I have a totally stable left command. With only red or red and wire I have a unstable left command.

Something even more funny, whith the wire alone on the orange common I can trigger a left command by touching the free end of the wire with my finger.

To be sure we’re speaking about the same point, I don’t touch the down signal point but the pin circled in orange on the slagcoin’s scheme. When I’m using the wire alone I can get a perfect down command without left parasites when linking the down pin with its ground.

ok, Im having a similar problem except when i hold down button 3 and press down at the same time the left input oscillates. It appears down and button 3 use the same common? Its my first hack and my electronics knowledge is pretty poor. I might have to pull apart another controller and try again

Same problem here with down and button 3. I wired both down and button 3 on a sanwa jlf and I get a lot of left commands when I turn around the joystick. And even some with the joystick at rest…

We can probably get around this issue by using buttons 9 and 10 for down and button 3 but it’s ugly as hell. I’ll stab this pcb to death and buy a cthulhu board instead.

I might be able to be of some help, but I’m very confused as to what exactly you’re doing, wire or not, if the connection is floating, it should not do anything, floating meaning only one point of contact, IE black probe on down and red probe floating. Now from the picture you showed (which isn’t the best schematic i’ve seen by the way) it seems that this is not a common ground pcb, I’m quite baffled at the different color commons that appears here, so without a pcb to test on I really can’t tell. Can you confirm whether it is indeed not common ground? or if it is? It’ll be alot easier to figure out whats going on with that established. I’m assuming for down you’re connecting the two orange circles together and you’re saying that you get a left input instead? Anyways assuming that it is non common ground, you’ll need to modify your stick a little to seperate the down microswitch ground from the rest, then it should work fine.

That’s the problem, it does something. With only one point of contact on the orange dot, the one between the green and pink ones, I can have left commands.
It seems to be depending on the wire length I use. With a really short one everything is fine but with a longer one, or is the latest case with a microswitch attached to it, it’s left commands frenzy.

It’s definitely a non common ground. Orange to orange ground, pink to pink ground and so on.

I was planning to cut or remove the joystick’s pcb.

I separated the grounds on the jlf and wired it to the tracks on the pcb at the switch, ill just use the select button for button 3. For the second controller ill hook it up as i did before and if the same problem re occurs ill put it down to shitty pcb :slight_smile: