My RCA 7.1 receiver keep blowing fuzes i replace them and then it blows them again when i turn it back on. everything else but the audio works. the model number is RV 3791F

Probably the output transistors have blown or the amplifier capacitors are dried out.

Fuses are there to protect you and the device from further damage. Repeatedly replacing a fuse without fixing the cause of why it keeps blowing in the first place isn't a wise decision.

are short in the audio output transistors may have been short since a channel 2 or maybe 4, also open resistance check carefully and change them after you put a 75w bulb in series 100w or where is the fuse clearly, you have to remove the fuse when you put the focus if all is well will turn on only a small incandescent and amplifier work well you put audio speakers and there will, if everything is well put the fuse back and ready.

Disconnect the amp and see if the fuse still blows, if not replace the amp

ok, temporary cheap fix... (i mean in a ******* engineering kinda way ;-) . . . )
since your primary receiver has a sub-out RCA plug, you can hop into the local pawn shop, buy a cheap receiver and an RCA line splitter, and connect the primary sub-out to the CD or any input EXCEPT phono (resistance is different on the phono rca's). remove the plate from the sub and run the speaker wire from the "pawn stereo" directly to the speaker. replace plate on sub to keep box sealed, and adjust receivers to desired level of bass & volume.
You have spent $50 and now have a decent sounding system again.

fuzes blow because something is overloading the equpment. First make sure you speaker wires are not shorted, or touching each other. If the speakers are not shorted out, unhook them completely and replace the fuze. turn on the equipment. if the fuze again blows (make sure its the same value fuze and not a higer rating) then you most likely have a shorted output transistor or transistors. In this case you will most likely need to take the device to an electronics service place, or if its under warranty send to the manufacture. Most often these devices cost more to fix than to replace, so its your call on that. If your handy with electronics, you could try and get the schemetic for the device and try to fix it yourself. If you have a shorted "final" or "output transistors" you most likely also have burned out driver transistors and also some resistors. It's unfortunate that today most things are "throw away". one more thing, if the device has a strong smell, then the chances are good that something burned out

Power cables are exposed either at battery area in engine or stereo compartment. Search to acquire and remend an exposed power wires else would blow all fuses.

Dissconnect ALL speakers from back of unit then try to turn on.
If it works you have a speaker short.
If not, you have a more serious problem.
DO NOT replace the fuse with anything else but what was specified, as it can cause a fire!

This condition, may be produced by defective components (Q506, Q507). you can remove those transistor, replace the fuses, power-on and wait for relays click. if the fuses not blown again, them replace both transistor.

Check the spkr imp. and if thats good make sure your levels are not to loud if all checks out you will need some service on the unit

could be several things, speaker wires touching,shorted output transistors, a shorted rectifier diode,bad filter caps in the power supply,those are the most common