mitsubishi VCR cleaning

You'll want to clean everything the tape comes in contact with. The easiest way to tell, if you're not familiar with a VCR innards is to take the cover off and then insert a tape and push PLAY. Their will be various guides, pinch rollers, audio and control head along with the round spinning video heads. Take particular care with the video heads, any up and down movement can easily break the delicate heads. The video heads will be on the lower most part of the rotating drum and their may be 2 or more heads. They'll be a dark color compared to the smooth drum itself.
Personally I like to use chamois cleaning sticks but foam will also work. Try and not use something like a Q-tip which can leave bits of fiber caught in the heads and tape path. I personally like to soak the cleaning wand with tape head cleaner and hold it against the drum. Then with my other hand I gently spin the head being careful to not let the foam catch on the delicate video heads, that's why I like chamois because it doesn't catch on the heads.
Finally put everything back together and hopefully your lines will have gone away. I suppose you could use something like Iso. alcohol instead of the tape head cleaner but don't use anything that will leave a residue or water.

The first photo is an overview of the VHS mechanism in an Emerson EWD2204. The second photo is a view of the VHS head drum, fixed heads and pinch roller in a Magnavox ZV450MW8A. The third photo is a closer view of the head drum with two of the video heads in view along the lower edge of the spinning portion of the drum in the same recorder.

Around 1998 I purchased a new Sony SLV-798HF. A few years later the VCR developed symptoms that resembled dirty heads ie lines in picture. I knew the heads were clean and I didn’t suspect worn heads. I think the roller guides went out of alignment. In my opinion the VCR wasn’t worth servicing so I chucked it and bought a new SVHS model.

Here is a sight outlining the 15 most common VCR problems.
See problem number 6-Roller Guides.
If your heads aren’t dirty or worn, this may or may not be your problem.

Depending on which model Mitsubishi is involved, there are additional considerations. Some production runs of late 1990s MGA SVHS models (but usually not their regular VHS lookalikes) have an obscure issue involving metallic shields that break down, bend, or corrode over time. This causes a short in the signal path coming off the video heads and results in the appearance of "lines" during playback that look very much like bad tape dropouts, ignition interference or mistracking. The models 760, 770 etc are especially prone to this. I've lost the link with the service instructions but the info is out there, google "Mitsubishi 770 false tape dropouts" and it should come up.

If cleaning does not help your problem with lines, your MGA svhs might need a pretty deep disassembly/realignment to get rid of it.