I will attach here some photos of opening of the EL-5/7. Both models are pretty similar except for the mechanics which are a bit more complicated in EL-7.
(This instructions are written purely out of memory and after looking at these photos and I don't take any responsibility over whatever you do to your Elcaset deck! Unless you get it working, that is. :scratch2
Remove the top cover by opening four screws (two on left and two on right side). When the front of the deck is facing you: on the left-hand side is the power supply board. This board has a hinge and after removing (or loosening) two screws the board can be turned down. (See photos). All cables from the mechanics section (the cassette compartment) can be unplugged from the power board as all the wires have connectors. But DO MAKE SURE you take photos or the original connection or mark the connectors (fe. use a pen and mark the pairing connector/plug) as it eases the connecting A LOT. The mechanics section has (2-4?) screws that attach it to the bottom plate. You also need to take off the tape compartment window (pull up) and remove the grey plastic panel on that covers the rear of the cassette compartment (two screws, accessible from the front). The you need to loosen the tape-head bridge, the two out-most screws. NOTE: do not alter the adjustment screws on the tape heads! Also note not to scratch the heads. See photos.
After removing those screws, the whole of mechanics can be lifted off the case. Then you should be able to visually go thrue the mechs. and by pushing the solenoids by hand you can feel which ones are sticky. All playback/winding modes are selected by activating one or more of the three solenoids. Use some electronics/switch cleaning-and-lubricating solution to carefully clean up the old grease and make the mechs. to run smoothly. DO NOT get any lubricating/oiling to the belt, capstans or tape heads.
PHOTO1: the insides of an EL-5 (cassette compartment("mechanics") on the right (front of the deck).
PHOTO2: power board loosened and turned aside, mechanics removed. Note the tape-head bridge loosened and hanging on the right.
PHOTO3: cassette mech, front view. Check the area where the white roller is, thats where the transport attaches to the reel-hubs. This part is usually most hardened and will move very stiffly.
PHOTO4: cassette mech, rear view. Motor on the left, three solenoids on the right.