Low voltage in the core

[SuperBad]

I just finished my core module, and I did like TK's page says and checked the voltage across certain pins in both the IC sockets.  I get a reading of 1.8V in each place.  I am using a 5V and 1amp Wall wart.  I am getting 5V at the input.  I just don't know how to up the voltage across the board.  Should I use a higher voltage power supply?  This is going into a Midibox FM.  Thanks for any help.

Bobby

[moxi]

there is somewhere here a post about your problem ,

to say that quickly: you must supply you CORE with at least 6-7 volt, the reg 7805 need at least this voltage to output the reguated 5V.

if you already get 5v @the input ,you have to remove the 7805 and to connect your power to J2 , as it 's shown here:

http://www.ucapps.de/midibox_lc/midibox_ng_switching_psu.pdf

but search on the forum ,you will find more information.

[Screaming_Rabbit]

if you already get 5v @the input ,you have to remove the 7805 and to connect your power to J2

... but then your PSU has to be regulated!!! I don't think, that this wallwart is regulated...?

Greets, Roger

[moxi]

to say that quickly

really quickly!... :-X

[moebius]

Hi,

We are talking 'bout DC here?

First of all at least Fairchild specifies V_Drop as 2v for LM78** series regulators. Second, if you  use J1 to power the core, there's additional diode drop from the rectifier.. it's 1,4v, isn't it? Much higher voltage than 5v DC is needed to keep regulator working as intended.

Well regulated 5v DC can be directly connected to J2 (with regulator removed).. I'd say "less well regulated" 5v DC can be put there too - if 5.1v zener (in a correct orientation) is placed between pins 2 and 3 where regulator used to be..

But for the Midibox FM - you'll need a bipolar power supply for MB_FM opamps. Not in a mood for searching it, but you can find a schematic from the forum that shows how single AC power supply can be used to power it. TK has said, there should be no problem running opamps as low as +/-5V.

Bye, Moebius

[SuperBad]

Thanks for the tips.  I did search for it..  The words voltage and core bring up a ton of posts.  I did not find what I was looking for though.  I Used the 5V because I had it nearby, and I just wanted to test the core module before proceeding further.  I have the FM module, and DIN modules ready, I just need to finish my DOUT.  Then I will be wiring the rest up to test it.  The 12v supply will be built soon, but I am very cautious when it comes to power.  I will be visiting radio shack today and trying to find a 8-9V 500ma min supply.

I appreciate the forums help with this.

Bobby

[SuperBad]

I got an adjustable wall wart from Radio shack.  9V 800ma seems to work nicely.  The bootstrap sends a Sysex message but. I couldn't  find the other midi cable, so I have to wait until tonight to upload MIOS.  Got my fingers crossed.