Firstly I'm sorry if this is in another thread, I looked around but could not find the same topic. So if anyone knows of a previous thread just point me in the right direction, and I will say sorry to all.

As the title says I recently bought a grey DMG-001 from Super Potato in Akihabara (Japan), got home put in my LSDJ cart, turned it on and only got the jumbled Nintendo sign. I repeated this many times after blowing on the cart and the cart socket in the DMG but to no avail.
I then tried this with a Tetris cart (I bought only for testing purposes) and had the same result.
I know these carts work because I have been using them on another DMG I have for a while now.
So before I decide to go back to Akihabara and talk to the shop people, I was wondering if anyone here has any advice so I can fix it myself.
Besides it was only 3000yen so it would be easier to fix before making a claim to the shop.

P.S the only thing that the shop stated was wrong with it, is a scratch on the screen.

Take apart the cartridge and clean it. If that doesn't work do that to the contacts on the gameboy. It's not a big issue.

sweet thanks for your quick reply, what kind of cleaner do you recommend?
just rubbing alcohol with ear buds?

rubbing alcohol should be fine. q-tips/ear buds are a safe bet too.

Sometimes I find that some carts don't work when pushed all the way in. This is very true for the EMS carts. What I do is push the cart all the way in, turn the game on and push the cart as far up as I can until it's stopped by the on switch. The "Nintendo" logo may be a mess but it's not until after the DMG makes the "bling" noise that I attempts to boot the cart.

You might try inserting and removing a cartridge in the slot repeatedly (10 or more times) if you don't want to disassemble and clean it.