Vu+ Duo red led issue, no access to the receiver solution.

Perhaps this is the problem of yours receiver.
So, Rs232, Usb etc not working, you have only a red led on the front display.

Research..
A good reference is to check the P704 (Jtag) pin 1, this has to be 3.3 V, in any case not be lower than 3V.
Is it low, or missing, check the inductor F808 if it is interrupted or bad.
Measure the two sides of the inductor, the voltage value has to be equal on both sides.
If not, replace it.

Inductor F808 function..
This inductor must feed the Serial port, Security chip, Jtag, (Tuners) Lnb control ic, Front panel, Cpu and probably more sections.
If the inductor is interrupted, all this will not work.

Removal, mounting..
But it is not easy to replace, because it is mounted close to the plastic Psu connector.
If it must be replaced, protects the plastic.
Use a piece of metal, or aluminum foil, or even better (if you have) a piece of Kapton tape.
In any case, something to protect it from the heat.

Inductor value..
Unfortunately, is the actual value unknown, I have used a 0.39UH inductor and works fine.

Good luck.

All the best about hardware/support from Johnny_B, link :
http://jb8a8f8.com
http://jb8a8f8.nl