Speaker hack and electrical pass-through questions

[solowCX]

Two questions, mostly concerning some electrical things.

First off, I ended up purchasing some speakers for my current cab build that met most of major requirements (right size, fair price and external wired controls), but noticed when I got them home that they have a soft power switch on the wired controls. Essentially, whenever they lose power, the power button has to be pressed again for them to work. The reason this is a problem is that I bought a Bits Limited auto-switching surge protector and would like to be able to turn the speakers off in order to get rid of the speaker humming. I have read some people have hacked their TV power switches to stay on all the time, so I was hoping something similar could be done for these speakers.

The power switch itself is very 'clicky' in nature, similar to how it feels to click on the left or right analog control sticks on an Xbox or Xbox 360 controller. I opened up the controls and took some pictures, which can be seen below. If someone knows a way to make these stay on as long as there is power I would really appreciate it.


Secondly, I have seen some projects in the past have had a sort of electrical passthrough on the backsides of the cabinet in which a standard removable electrical cord can be plugged in (like most computers). Ideally I would like something that could be installed into a hole in the cabinet that would have this outlet on the outside and have a plug for my surge protector on the inside. Does such a device exist, and if so, what is it called? Or what components are needed to assemble something like that?

Thanks for the help everyone.

[Blanka]

This board looks like it has very simple stuff on it. Nothing audiophile. No (pre)amps on this. I only see 2 potmeters that probably change the volume/balance. The transistors with resistors probably work as a electronic on-off switch. So why don't you get rid of this board completely? Set the volume with the computer, and connect the sound signal and power through directly (what are the six cables coming in?).
Can you photograph the amplifier as well? If it is a single-chip switching amplifier (D-class), then there is no big deal in leaving it on permanent, as power-use in idle is very low on these amps.

[Blanka]

Look among these items:
http://nl.rs-online.com/web/search/searchBrowseAction.html?method=retrieveTfg&Ne=4294957974&N=4294954277
RS-Online has worldwide offices, so don't be fooled by this dutch site.

[solowCX]

Ideally I would like to still use this board, as one of the reasons I chose this set was for the external controls. I was merely hoping there might be some simple way to rig the power button to always be "on," thus turning the speakers on whenever power is restored.

The left/right speakers and control board actually all end up meeting at the end of their strands into what looks to be a standard serial connector. I am assuming that the 6 cords going into the board are for left/right speakers, headphone jack and possibly subwoofer (as you can control the bass level from this board). A picture is attached of the connector going into the subwoofer.


As for the power modules you linked to, there are definitely a lot of choices there... I really don't have a lot of electrical experience though, so forgive me for asking if there might just be one that you can just plug a standard male 3 prong US adapter into on the back? I can't really tell from the angles of the pictures, but I am guessing that these would need to be wired?

Thanks.

[Blanka]

Then you probably need to draw a scheme of the whole board and post it here. Guess it has 2 sections. Audio-control and power-on-logic. The second one must be quite to disable.

[pmc]

I think that's just a momentary switch. Can't you just jumper the two connections under the button so that it's "always on"?

-pmc

[NickG]

If you hold the button down and the speakers stay on then that is true.

However, there are four connections in the button...two paths?
It is possible that having two paths helps to create the on/off toggling circuit,  (the two transistors closest to the extension cord as Blanka stated) and you may need to solder across only two poles (not all four.)  This is likely the situation if the action of holding the button down when powering it on eventually powers it off as well.


I think the six wires are:
Headphone Left and Right  = Green and Yellow 
Ground = Black
+Volts = Dark Red
Volume and Bass attenuation level = Orange and Red
 

[solowCX]

If the button is held and power is restored the speakers do not turn on, it needs the actual press of the button for power to be restored. This is even if the button is held as power is lost, or if the button is pressed and held after the cut-off and then restored.

If the button is held down while the speakers are on normally they turn off immediately, not when you let go of the button.

[NickG]

That seems to make sense.  I would just try to short across one of the contact pairs (then the other pair) of the button while powered (without pressing the button to see if that turns it on.  No! Wait, don't do that yet!  Looking at the solder side photo of the PCB, the button has six solder points.  When the button is pressed the East most is probably shorted to the Southeast and the  West contact shorts to the Southwest?  This is most likely, but it may short them all together instead.  You could verify this with an ohmmeter before doing any potentially hazardous live testing.

[solowCX]

A better understanding (or really one at all) of electrical engineering would probably help now then . Actually don't have anything on hand to solder with, or an ohmmeter for that matter. Would a multimeter do the same as an ohmmeter, and what would I need to be checking for on the solder points?

Thanks for the help in looking through this stuff, I'm sure I could have guessed it wouldn't have been as simple as cutting a wire or something.

[NickG]

In the end, it may be that simple.  There is an ohmmeter setting on most multimeters   Imagine your multimeter leads as a switch.  When the leads are touching, it is closed (pushed)  When they are not touching, it is open.  Now touch the leads to the switch contacts instead of to each other.  If they are normally open contacts, then they should have continuity when the button is pressed:
On most ohmmeters(Ω) continuity reads as a low resistance; zero ohms or something very close like 0.03 ohms.
You may need to ensure that the PCB is disconnected from the sub-woofer unit if you take these measurements or you may read back across the board in it.

[Blanka]

It is a flip-flop like circuit that needs a pulse to get in the prefered state. Same as computer-power-switches.
Seeing the board, it must be not difficult to bypass it, but I need the scheme to help you with that. You can also try the capacitor hack for computers:
http://www.pealefamily.net/tech/newmame/captrick/

[severdhed]

if you unplug the speakers, hold the button down, then plug them back in, while keeping the button held down, do the speakers stay on?  if so, you technically wouldn't need to solder anything, you could used a zip tie or something similar to go around the board and hold the button down for your.    if not, then you will have to listen to one of these other guys and probably solder something.

[solowCX]

It is a flip-flop like circuit that needs a pulse to get in the prefered state. Same as computer-power-switches.
Seeing the board, it must be not difficult to bypass it, but I need the scheme to help you with that. You can also try the capacitor hack for computers:
http://www.pealefamily.net/tech/newmame/captrick/

What would need to be done to create this scheme? Again, I don't have a lot of electrical experience, but would like to be able to provide one if possible.

if you unplug the speakers, hold the button down, then plug them back in, while keeping the button held down, do the speakers stay on?  if so, you technically wouldn't need to solder anything, you could used a zip tie or something similar to go around the board and hold the button down for your.    if not, then you will have to listen to one of these other guys and probably solder something.

If the button is held down when the speakers turn on nothing happens. The button only works once power is restored and you press down on it, at which point they immediately turn now, not when you let go of the button. So yea, likely will need to do some other sort of trickery to get it to stay on.

[solowCX]

Sorry for the delay with this topic. Finally was able to test the Ohms for the 6 points NickG suggested.

I tested the vertical pairs and it seems that the 2 on the far sides are normally open, while the 2 in the middle produced higher ohms (around 5 or 6 megaohms) when the button was not pressed and low ohms or no ohms when it was pressed. I tried various combinations of the 6 with the leads and got ohms for the most part I believe when the ones on the side were linked with the ones in the middle.

Does this mean just causing a short between the middle ones will cause it to always stay on when connected to power?

Thanks for the help everyone.

[solowCX]

message deleted

[Zebidee]

I suspect that your speakers turn on after power is cut to the middle momemtary switch.  What that means is that you need to let power flow first with the switch in an closed state, THEN press the switch to open it and trigger the speakers to turn on.  Otherwise, the speakers just get a closed switch when the speakers are turned on, which triggers nothing.

You could try the peale cap turnon trick, or a variant on it, which Blanka suggested earlier.  You would need to bridge to two contacts of the middle switch with the capacitor.  Note that polarity is important with electrolytic caps.

What the cap will do is allow current to flow (closed state) until it is fully charged (a second or two, I guess).  Once fully charge, caps become open-state and won't pass current.  So, you effectively create a delayed switch-press, which is what we want.

Without having your speakers in front of me, I can't be sure or exactly which terminals need to be crossed by the capacitor, but I think that the cap trick is possibly the solution for your problems.  You'll need to solder ...

I tested the vertical pairs and it seems that the 2 on the far sides are normally open, while the 2 in the middle produced higher ohms (around 5 or 6 megaohms) when the button was not pressed and low ohms or no ohms when it was pressed. I tried various combinations of the 6 with the leads and got ohms for the most part I believe when the ones on the side were linked with the ones in the middle.

Does this mean just causing a short between the middle ones will cause it to always stay on when connected to power?

Thanks for the help everyone.