Why does my dvd player not play

SOURCE: plays cds but wont read dvds

upgrade the firmware on the product.

SOURCE: doesn't read dvd's

This problem is down to failure of the laser and an only be solved by replacing it. Samsung are aware of this fault but will only offer a free replacement if the unit is still covered by it's warranty.
They do offer a replacement service but charge £94 for it.

SOURCE: Won't play

Fixed it! I got a new laser/optical pickup (SF-HD65) and replaced the old one. Replacing it wasn't too hard, just a little fiddly. Once it got it all back together, I fired up the unit with the case open and could easily see the red glow of the laser through the spinning disk. This didn't happen with the old pickup. Every disk I put in (originals and burnt stuff) was detected.

Even though the new laser worked, I can't be 100% sure the 24 pin ribbon cable / flat flex cable (ffc) connecting the laser to the mainboard isn't dodgy (I didn't try the old laser again). It's very flimsy and I may have somehow managed to re-seat the connectors better or bend the cable enough to make a contact over a break. If I get the "no disc" error again I'll replace that with the same or similar. For all out there it has the following written on it Kotobo E188165 AWM 20798 80C 60V VW-1. It's about 25 cm long, has 24 pins.

Regardless, I'm happy I didn't send the player to landfill. For $15 + shipping, replacing the optical pickup was cheaper than buying a new player that plays as many formats.
T1mb0

SOURCE: pioneer xv htd520 won't play dvds

This is a common problem for this model. It has a memory IC that must be replaced. This is a surface mounted IC that requires exceptional soldering skills to replace. I work at an authorized Pioneer service center and have repaired a good number of these for this exact problem. Unless you have great soldering skills it is not something that should be attempted to do yourself, it can cause permanent damage to the board if not done perfectly.

If you have the proper skills and soldering equipment I will be happy to give you the Pioneer part number so you can replace it yourself. If not, then you really should just take it to a service center and have a professional do this.

Let me know if you would like that part number.

Dave

SOURCE: SONY DVD-CX995V "cannot play"

In that symptoms optical block (lens) sounds defective and requires replacement.
Let me know if you want to replace optical block by yourself to provide you more technical info.