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Thread: Mastero MK-4.5 250w 12v DC-DC ATX PSU + SDC

  1. #61
    Variable Bitrate
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    This is how I do the test.
    1 DVD ROM and 1 DVD+-RW by Maddog Multimedia both rated at 2A on 12V.
    2 WD HD (40G and 60G) 7.2K RPM 0.24A on 12V.
    Each IDE channel has a HD and a DVD
    Copy 1 550 MB ISO image file from one HD to the other while 1 DVD playing music CD and the other play DVD movie. All running fine for 15 min while engine off, start car, and run for another 10 min. No reboot, no problem and the setup is in the Supra.
    Of course, I only have one DVD ROM and a HD as part of the setup.
    I still maintain that you might be pulling 2A at most.

    Even at 2A you would be dissipating ~24W in the LM1084, wouldn't you?
    Its reasonable that with appropriate heatsinking the LM1084 would live with a 24W load on it. The temp. rise with a decent heat sink (one that can do 1.3C/W, which is still on the optomistic side) would be 100C in still air. As long as the room isn't 50C then the chip will live fine. Throw in some forced air and it is well within its operating range.

  2. #62
    Raw Wave
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    The newer design uses a switcher to boost to ~24V and then a linear regulator to drop back to 12V.

    Wow thats 12VxA to loose as heat in that linear regulator. As Mr P said why not just have it just above the minimum input voltage of that 12V regulator

  3. #63
    Raw Wave rando's Avatar
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    50C ambient (or higher) is totally plausible for trunk mounted units with no forced air, don't you think?

  4. #64
    FLAC Mastero's Avatar
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    The mk4.5 uses two 12v@5 amps

    The LM1084 require min 17v to give out 5 amps. The 24v boost input is not running on 5 amps R&D showed the 24 drops while 1084 gives out 5 amps and mantaining a constant 12v out... had done some calculations shall find it and post it..

    Also its a rare case the vehicle will drop to 8v while crancking ...... my mercedes C250D drops to 10.8 max with parking lights on went to 9.5 max .

    No computer components use full power 24/7 its only during start up for say a max 3~5 secs.

    Boosting to 15v shall be a close cut as the vehicle charging system goes to 14v during running .. and if there is a faulty rectifier in the altenator and the charging goes a volt higher, then you have input and output at the same volt which will cause undesired result with the 2587.

    In simple i have used the PSU for non stop 14hurs during my trip to Goa and it did not show any sign of strain or over heating ofcourse has a 2" fan for colling. Played Mp3's and dvd.

    I hope this helps all.!

    Cheers
    Mastero

  5. #65
    Newbie
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    Jun 2004
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    Update.

    I made my board using apositive photoresist. Left outside on a cludy day for 20 mins. SInce I didn't have any etchant I made my own from a recipe on Diyaudio.com basically it's 33% HCL (from Homedepot) and 3% Hydrogen peroxide. ** If you think you're being careful enough, you're not.** I was in full protective gear and whatnot and the acid still irritatedd my lungs. No more sinus trouble I assure you. Works great though, took like 15 mins to etch cause I didn't mix it 100% accurantly, but the board came out superb. only one 4 millmeter section was slightly worn on the edges, ie. the holes for drilling the component leads. So far I have all the chips in and inductors. working on the capacitors. Using a 20/40 switchable Radio shack soldering station ($20) works great. As I go over the pcb, I am manually tinning the traces with solder.
    I got all my parts from digikey, came within 5-7 days. the LMXXXX regulators I got free from national, $8 shipping ARGH! but they give you 5. You do the math :

    Two questions though Maestro.
    1. I haven't soldered in awhile and my first component I soldered in, well I got it freakin' hot. Soo, what is the worst case scenario of a fried BD677 ? Can I tell if it's bad before I apply the juice to the final circuit?

    2. I can't find the MAX 788 CCK & MAX 787 CCK at digikey or anywhere else. When I put in the whole name, nothing comes up. If I put in CCK things come up, but I have no idea which ones are drop-in as a replacement? What are those two things anyway?

    Sincerely,

    David

  6. #66
    FLAC Mastero's Avatar
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    Quote Originally Posted by Eternalightwith

    Two questions though Maestro.
    1. I haven't soldered in awhile and my first component I soldered in, well I got it freakin' hot. Soo, what is the worst case scenario of a fried BD677 ? Can I tell if it's bad before I apply the juice to the final circuit?

    2. I can't find the MAX 788 CCK & MAX 787 CCK at digikey or anywhere else. When I put in the whole name, nothing comes up. If I put in CCK things come up, but I have no idea which ones are drop-in as a replacement? What are those two things anyway?

    Sincerely,

    David
    First use a DMM to test the BD677 ....

    try www.maxim-ic.com

    Cheer s
    Mastero

  7. #67
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    Quote Originally Posted by Eternalightwith
    I have all the supplies I need to make the PSU and I was wondering if you got the chance to test it out? LIke was there any errors or whatnot? Shouldd I wait till version 2 comes out with the addon functions?


    David
    Have you had a chance to build/test this yet eternalightwith?

  8. #68
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    Mastero, are the kits avail yet??

  9. #69
    FLAC Mastero's Avatar
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    Quote Originally Posted by ph0tix
    Mastero, are the kits avail yet??
    JUST working on it ... shall be avalible soon say a day or two...


    Mastero

  10. #70
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    Jun 2004
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    errr

    No not yet. I'm going really slow at it, and soldering a few components a day.

    I did have another quest for Maestro. You're plans said a Relay type x,y,z
    So I type that in and I get 100's of different types of relays. So I pick the closest one that has the required tolerances to Volts/Amps. Thing is, when I got it, it had 5 pins on it. 3 on the left and two on the right, I think. have to go home to doublecheck. Problem is that the PCB board was like I think 7-8 holes for that component. So I am a little confused as to what type of relay I should have.

    David

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