Pre-pot is definitely the way to go. It's a bit louder and punchier as well (at least using the pre-pot points I have, as opposed the soldering onto the pot like I have on my other DMG).

Gonna check again when I have the time. Didn't notice the power LED 'cause I have a 'Chip Music In Stereo' lens from kitsch fitted The backlight was on though... Not sure if that means anything.

Taking it apart and re-assembling it numerous times may have wrecked the ribbon cable that connects the two boards together, which could explain these problems. This is a common problem that not a lot of people seem to realize. It sounds to me like there's a bad connection between the boards, and the thing about removing the speaker was just a coincidence.

Anyway, again, solder to pre-pot. It's not affected by the volume pot (hence pre-pot) and you can just turn the volume down to mute the speaker without affecting the pro sound output.  There's no point in removing the speaker with a pro sound mod.

Edit: Or hopefully you just didn't plug the ribbon cable in, as Kitsch said.

i bet you didn't plug the ribbon cable back in   it happens to everyone, to me constantly...

if the power LED on the front is coming on, but no image on the LCD screen, try adjusting the contrast dial.  still no luck, take it apart, take the ribbon cable out, clean the contacts wth some rubbing alcohol, wait till dry, put it back in, try again.

if the red power LED isn't on, and the LCD is dead, you missed getting that cable plugged back in most likely.

you could have inadvertently made a solder bridge between the two leads of the speaker.  since you desoldered it, its possible. 

patience and a cool mind.

Haha really? Man... Every time I've opened it up, something wrong has happened to it! The screen is completely dead at the moment. Time to open it up again... Wonder what will be wrong with it this time

I think I just need to sit down, completely dismantle it, check everything and put it all back together very carefully

That's really weird. You could also just snip that white wire on the stock speaker, right? I'll double check that, but I think that works.

yeah, wow, that's really weird. i wonder if you left some stray solder somewhere and that caused it to glitch out.

i usually just yank the speakers out by hand. no need to desolder anything, in my opinion.

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shouldn't have happened.  weird.

De-soldered the speaker and it ended up messing with everything (screen went blank, no sound at all)...!

Not sure if it's because of my dodgy soldering or if the speaker needs to be connected for the circuit to function 100%... Soldered the speaker back in and everything works again. I'll just leave the speaker how it is. Not too bothersome

Cheers for the suggestions!

I knew I was forgetting something

Or do something much less destructive and just solder to pre-pot and turn the volume down...

Your easiest solution is to just clip the internal speaker, would that do?

3 options:
1) Cut the end off a busted 1/8" cable and stuff it into the headphone jack.
2) Remove the speaker.
3) Install a switch for the speaker.

That's how it works

Just fitted my DMG with a Pro-Sound mod. Sounds great! Only thing is, the sound is coming out of the 3.5mm jack and also the speaker at the same time... Not sure if that's what it's supposed to do...? If I plug into the stock jack, the speaker cuts like normal, but keeps going if I plug into the newly fitted jack...

Any suggestions?