Repair/refurbishing: MG100DFX

Discussion in 'The Workbench' started by slowcorrado, Aug 21, 2019.

  1. slowcorrado

    slowcorrado New Member

    Joined:
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    Location:
    Central PA
    It's been almost 4 years since I stopped fooling with broken amps and instead bought a house, renovated it, and moved. :) The itch has caught up to me though. I picked up another project from my local Craigslist. This was a non-working MG100DFX. It is "well worn" and the previous owner says it blew a fuse. (Yes, I'm aware this is usually the TDA7293) He then said "Well, it does come on, but has no sound, the fan is quiet too.".

    As always, I was skeptical and didn't even plug it in before I opened it up. (Expected to see all types of burn marks!) I looked over everything and found some weirdness right away. Strangely enough, the fuse is OK.... Here are a couple pics with some questions for anyone who has any experience with these models:

    Resistor R15 is only connected by 1 leg? The schematics show it as being connected properly. Is this something that people do to "mod" the amp? The other possibility is that it broke from rough handling or extended heat/use. Here's a pic to show that it seems to be broken off below the board's surface (and therefor not intentional). Opinions?

    (click the thumbnail for a nice closeup view)
    [​IMG]

    The next issue is the TDS7293. It looks like the back pin (2nd from the left) has a large solder blob on it that's shorting pin 1 and 3?! It doesn't look like a replacement, more like the solder was just too thick from the factory. Opinions on this? The center back pin doesn't look soldered at all! I'm going to certainly pull the module and see if I can get that desoldered/repaired before I even think about putting power to this thing.

    (click the thumbnail for a nice closeup view)

    [​IMG]

    That's about it for now. I'm really excited to start messing with it, but I may also do a youtube video to document the process (and that takes extra effort for sure!).

    Thanks for reading this far and any insight you may offer.
     
    anitoli likes this.
  2. ampmadscientist

    ampmadscientist Well-Known Member

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    Start the reactor... Free Mars!
    I have 3 of those power module boards if you need one.
    Also there is a zener diode that should be replaced...
     

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