Laptop remote switch - where to solder exactly ?

**frontliner** · 02-14-2007, 05:59 AM

Hi,

I've currently completely dissassembled an IBM 390x that i plan to use as my future carputer...

I'd like to know what solder points to use to connect the wires that goes to the remote startup switch.There is 6 points that could be used and i don't know which to use. So, here's some pics :

switch side view :

solders side view :

The button is a 6 pins through the PCB but there is also 2 others and one of them is marked M on the side of button.

On the solder side, u can see that b (see on scheme attached) is linked through a circuit to g (other pin of the same button).

I have taken the measures on the solders (ohmmeter at 200 value) :

- on d and + on e : OFF gives 1 . and ON gives 00,8
- on a and + on b : OFF gives 1 . and ON gives 00,8 (same)

scheme :

So, IS IT RIGHT if I solder a wire on d and the second one on e to have my remote startup button working ?

Thanks

**Wiredwrx** · 02-14-2007, 12:32 PM

Resistance matters not.

Put a continuity tester to the various pins, and check for continuity when the button is pushed.

Any 2 that have continuity when the button is pressed, should be sufficient to start the computer. You can then jumper those 2 to test it.

Michael

**frontliner** · 02-14-2007, 04:22 PM

Originally Posted by Wiredwrx

Put a continuity tester to the various pins, and check for continuity when the button is pushed.

If u mean the diode tester, i did and got the following results :

- on d and + on e : OFF gives 1 and ON gives 001
- on a and + on b : OFF gives 1570 (??) and ON gives 001

If i reverse the polarity :

+ on d and - on e : OFF gives 1 and ON gives 001
+ on a and - on b : OFF gives 1 and ON gives 001

All other pins checked gives 1

So, it seems to confirm the previous results obtained with the ohmmeter...

Now, about the volume potentiometer that i'd like to wire too...

Normally, i guess a potentiometer has 3 pins. Here it has 2 at opposite sides and 5 in line (left side on the pic)...

How can i test here ?

Thanks.

**Wiredwrx** · 02-14-2007, 05:14 PM

Originally Posted by quark

If u mean the diode tester, i did and got the following results :

- on d and + on e : OFF gives 1 and ON gives 001
- on a and + on b : OFF gives 1570 (??) and ON gives 001

If i reverse the polarity :

+ on d and - on e : OFF gives 1 and ON gives 001
+ on a and - on b : OFF gives 1 and ON gives 001

All other pins checked gives 1

So, it seems to confirm the previous results obtained with the ohmmeter...

Now, about the volume potentiometer that i'd like to wire too...

Normally, i guess a potentiometer has 3 pins. Here it has 2 at opposite sides and 5 in line (left side on the pic)...

How can i test here ?

Thanks.

No, I do not mean the diode tester,I mean the continuity tester. USUALLY, the meter beeps when there is a connection between the probes. Put the probes to different pins, and push the start button. If it beeps, there is continuity, which is WHAT A BUTTON DOES. You now know WHICH pins get connected to start the computer.

Michael

**frontliner** · 02-14-2007, 06:15 PM

...don't have that kind of beep tester on my mutimeter, sorry!
I came here 'cause someone told me exactly the same on another carputer forum...

I have read today from different sources that 'continuity testing' are done with a ohmmeter. And logically it could also be done with the diode tester (signal passing one way/blocked on the other)...

Could someone tell me what to do only with the measures i could give ?

Concerning the 5 pins on the volume potentiometer, it seems it's because it's a stereo and not a mono...

Thanks.

**Wiredwrx** · 02-14-2007, 06:21 PM

O.K., with the Ohm meter, put it in the Ohm setting, and with out touching the probes to anything, what is the reading. Now, touch the probes together and note the reading. That second reading is what continuity is. Now, place the probes on the pins, and push the button. If the reading matches the reading when you touched the probe together, that is continuity, and the pins that should be used.

Michael

**turbocad6** · 02-14-2007, 06:55 PM

your making way to much of this.... just guess at any 2 pins... touch them momentarily.... if the PC starts your good, if not, try another combo.... there is no way you can damage it buy doing this.... the switch has one ground & one of the pins are looking for ground to start... that's it.... there is no power at the switch on any laptop I've ever modded....

if your paranoid about trying this method then pick up a tiny one amp fuse to use inline of your jumper, or test for any power at the switch.... theres no reason too, but this may make you feel a little more comfortable doing this.....

**frontliner** · 02-14-2007, 06:58 PM

Originally Posted by quark

I have taken the measures on the solders (ohmmeter at 200 value) :

- on d and + on e : OFF gives 1 . and ON gives 00,8
- on a and + on b : OFF gives 1 . and ON gives 00,8 (same)

My meter is an electronic one (Elix LX-830B)...

Meter ON, not touching anything = 1 .
Touching probes together = 00,8

So, continuity mesures are corresponding with the one taken in my first post (see above)... There is continuity when button is ON (00,8)...

So, i guess i can wire d and e as i said previously...

And what about the volume potentiometer ?

Here's another pic (view under the PCB/other side where is the potentiometer). Notice that there is a chip --> could it be a numeric potentiometer ? :

**frontliner** · 02-14-2007, 07:05 PM

Originally Posted by turbocad6

your making way to much of this.... just guess at any 2 pins... touch them momentarily.... if the PC starts your good, if not, try another combo

OK, thanks... but i can't really do it that way because the computer is at this time completely dissassembled. I'd have to solder, then re-assemble all parts and then start it up to test... And if i did a bad choice, i'll only have to dis-sassemble again all parts because the pins of the startup button on this laptop are located under the motherboard and not accessible without taking all parts out of the case...

So, i have to be sure near 100% about my solder before re-assembling...

**turbocad6** · 02-14-2007, 07:14 PM

yeah, well I've been able to bench test laptop motherboards without anything connected to it but the power.... it doesn't need to be assembled & complete, just make sure it's on a non conductive surface & plug the power jack into it.... once you hit the right combo just unplug it & solder away... you don't need the screen or the hardrive connected to it for this.... I guess leave ram in it, but it should come on even without that...