Can't open fuse compartment on gemini mixer to replace it

Try radio shack or ace hardware

There are several possible solutions for this. The cheapest and easiest is to do the following:
Solution 1:
1. Get an RCA stereo plug to 3.5 mm plug. This will go from your mixer to your computer. This will not be the highest quality, but will work.
2. Get an XLR cable of the length you need. I would guess a standard one with a male connection on one end and a female on the other. Connect this to your powered speaker. Also, this is a guess as you didn't include the type of powered speaker, so I can't tell you for sure which cable to use.
Solution 2:
1. An alternate idea for better sound quality would be to run a D/A converter similar to this one: http://www.sweetwater.com/store/detail/USBMix/It would give you a much higher sound quality for everything. You would run from your Gemini to this. From this device, you would run a USB cable to your computer, and a 1/4" cable to your powered speaker.

Line level output of the mixer would go into the line level inputs of the EQ, and the EQ line level outpputs to the line level inputs of the amplifier. If you are faced with a mix of unbalanced inputs or outputs, to balanced inputs or outputs it gets a little complicated because you need to matrix the balanced signal to unbalanced load and vice versa. There is no single answer to doing this either.

RCA jacks are unbalanced, 2 conductor 1/4 inch connections are unbalanced most of the time. XLR and 3 conductor 1/4 inch jacks and plugs can be either balanced or unbalanced.If either are wired so left and right are a single ring or tip on the 3 conductor 1/4 inch jack, it is unbalanced and they would share a common ground lead. XLR wired with one pin common with shield and right and left have a single conductor on the plug or jack, that is unbalanced.

typically (unless your useing other gear besides mixer and amp) you'd come out of the L/R outs. ( Main outs ) to the Main inputs of the power amp then out to your speakers (outs of power amp). Now the amp could be in bridge mono or other factors but typically, like i said, just
Mixer Out- Amp In- Amp Out- Speakers.

You would NOT connect an audio signal to the "send" jacks... those are OUTPUTS... In doing so you are driving signal backward enough to get to the headphones. Sends and returns are NORMALLY used on a mixer for external effects. You should either be using a LINE input jack or one for "tape input".

Don't even think of using a universal adapter !!! I could not find the schematic of this unit, but other Gemini mixers like this use center tapped AC power transformers. Any universal adapter will be DC, not AC. I have found that the FX7000 indeed uses an 18 VAC adapter... Try this as a source:

http://www.topdjgear.com/gemini-110vac18v.html

A large amp like this likely has protection circuit (probably a relay) that doesn't connect the speakers until the amp is stable and balanced. You relly need the schematics for the amp.

you need RCA to 1/8 inch stereo into the line in on the computer.

You can probably patch the audio into the audio input jacks of the TV, however without a video signal there would be no picture on the TV, only audio... It is also possible that without a video signal, the TV may mute the audio inputs...