monokinetic Posted April 7, 2006 Report Share Posted April 7, 2006 Hello all,Well I have everything hooked up for my MBSeq but I think I have run into a power issue. I have a setup the same as TK's, so 2 x LCD's plus 32 LEDs. I have MIOS1.8 and the latest MBSeq app. The only "non standard" thing I have is that I replaced the B40C800, which is unavailable in the Czech Republic, with 4x 1n4007 diodes, as recommended on the forum. I supply the box with 7.5v from a 1000mA wallwart.Anyway, turning on the MBSeq with everything attached all loads up fine, but after 3 or 4 minutes there is a worrying "too hot" smell coming from the 7805 and its too hot to touch! I did a bit of research through the forum and this seems predictable as the 7805 is only designed to deal with 1a loads. I have checked my LCD's manufacturers website and trawled the net for a datasheet which mentions how much current they draw but I haven't come up with anything. To be sure I know I could break the power lines going to the LCD and use my multimeter in series to measure the current drawn, does anyone know an easier way of doing this though?Lets assume for a moment that my 7805 isnt happy :) I know maybe you are going to suggest clamping a heatsink to it but I'm a bit worried that it is going to blow, do you think that's likely? The only other strange behaviour I have from my setup is that when I try to adjust the backlight and contrast trimmers they make almost no difference to the brightness of the screens, which seems a little odd.I have looked through ucapps for an alternative power supply and I know TK uses the switching P.S.U. for his MBseq, however I don't want such a physically large supply if I can help it. What are other MBSeq builders doing for their power requirements?I know various people are working on the MBPSU in another thread, I have followed it and I must say it looks perfect for the MBFM which is sitting on my workbench next to the sequencer! But it still uses a 7805 so it doesn't get around this 1a limit.I did a bit of research about this and came accross the LM317, which seems to handle up to 1.5a so I put a post about this here: http://www.midibox.org/forum/index.php?topic=6300.msg39036#msg39036It seems that maybe I was considered to be hijacking the thread, hence a new thread here!So what do you think, should I just risk heatsinking the 7805 and not worry about the heat? Or should I take the plunge and try to build a LM317 based PSU for heavy load Midiboxes?TIA for any helpDave mKps I just found a message suggesting this as an easyway to up the current:http://repairfaq.ece.drexel.edu/sam/samschem.htm#schslp2seems a bit over the top though to me! Quote Link to comment Share on other sites More sharing options...
moebius Posted April 7, 2006 Report Share Posted April 7, 2006 Lets assume for a moment that my 7805 isnt happy :) I know maybe you are going to suggest clamping a heatsink to it but I'm a bit worried that it is going to blow, do you think that's likely? Oh, damn.. If it blows You are definitely going to bankrupt! The 7805 is over current and thermal protected anyway, so You might want to try that heatsink ;DAnother possibility could be bypassing the regulation for the backlight and it tap directly from the PSU (You'll have to use current limiting resistor there)Moebius Quote Link to comment Share on other sites More sharing options...
monokinetic Posted April 7, 2006 Author Report Share Posted April 7, 2006 cool, I was just checking, didn't want my nice shiney LCD's all frazzled ;DThanks for alleviating my worries so quickly!D mK Quote Link to comment Share on other sites More sharing options...
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