Connecting..

[opus.quatre]

Hello there..

I wanted to power my Preenfm2 with an external 9V power chord.. Plus is at the center..
The blue leds flashed once, and that's all.. After a few seconds, the 7805 was terribly hot..
And I've been taught that electronics do need smoke.. Components are full of smoke, and once you let the smoke escape from it, then this component no more works; or very badly.. So I stopped immediately..

So my question is : which is the polarity and the voltage of the external power supply that we are supposed to use ??
Plus at the center ? at the periphery ??
And what will be the problem if anyone plugs a power voltage that would be polarity inverted ??
I wonder if I'd rather unsoulder this power supply entry, and have my preenfm always powered by USB..

Second question is :
About the MIDI sockets : I must connect pins 2 and 4 right ?? And there's no polarity, right ??

Thanx in advance for all your possible and wise answers..
And enjoy the rain..
Thierry

[Xavier]

Hi,

9V, + at the center, should work.
That's strange.
Check that your power supply does not provide more than that.
The 7805 is hot, but that should not be a problem.
Reverse polarity should be blocked by the diode D2.

But smoke is a problem ! Maybe a cap in the wrong polarity ?

Midi polarity is important and is explained here :
http://ixox.fr/preenfm2/build-it/the-case/

[opus.quatre]

Merci Xavier..
No, there was no smoke, I was just kidding.. But still the 7805 was very warm, and nothing was working..
I checked the capacitors, and they are correctly souldered in the right polarity.. And so are the diods, and so is the 7805..

ANd stupid me, I searched for the MIDI connection in the build page, I didn't think it could be in the "the case" page.. Thanx again..

Have a nice evening..
Thierry

[Xavier]

First verify you have JMP1 shorted. But if the 7805 is hot i assume it's OK.

I verified and saw you have a kit with a LCD display.
Is the LCD brighter when you switch on the preenfm ?
Have you tried to turn the contrast pot ?

Then check the different voltage as shown in the message #6 of this thread :
http://ixox.fr/forum/index.php?topic=63509.0



Xavier

[opus.quatre]

Désolé, Xavier, pour mon retard à te lire et à te répondre.. ET merci pour le temps que tu consacres à mon (petit) problème..
Maybe I didn't say that my PreenFM2 works correctly when powered by USB..
It simply doesn't work ONLY when I power it through the 9V entry..

"Is the LCD brighter when you switch on the preenfm ?"
Not sure I understand the question.. Brighter than what ? Brighter than when switched off, of course..
When I plug the 9V, the blue leds will be "on" for one or 2 seconds.. Unstable,  but on.. The LCD will be lit; or say bright, for the same amount of time.. But nothing appears on the LCD.. No welcome message or whatever.. and the 7805 will start heating the room..
That's why I ususally don't stay more than 5seconds..
Then I unplug it.. And if I immediately plug the 9V again, then nothing happens.. No blue led, no bright LCD..

And I don't know where is my multimeter, so I can't check anything for now.. I will, when I find it back..

But when plugged and powered through USB, everything works perfect..