Vertical hold problem with dvd player

[Cubbie]

Hey guys. I'm new here and although I'm not completely stupid about electronics, I am new to trying to repair things. I decided to take a deluxe piece of crap Coby dvd player as a learning project. I know it's not really worth fixing, but I figured if I screw it up to the point of no return it won't be a big loss.

Anyway, it just has a general vertical hold problem with no color in the picture, just black and white. It rolls all the time, not just while playing dvds. The audio is there and it plays dvds, the vertical hold is the only problem. It seems like a sync issue, right?

I opened it up and gave it a visual inspection. Nothing looks bad. Nothing is burnt out, nothing is busted or loose. So what I need is somebody to point me in the right direction. What do I need to test? Where should I start? I've tried a lot of Googling but I haven't found anything yet that addresses my particular issue.

Thanks to anybody who helps me out. I'm just trying to learn something new here but I don't have anyone around to help me get started.

I look forward to learning from everyone here and hopefully soon I can learn enough to help out others as well.

 

[(*steve*)]

Could it be an NTSC/PAL issue? I recall that one shows as B&W when you attempt to view it on a TV of the opposite type.

But I may be way off base here.

 

[Cubbie]

Could it be an NTSC/PAL issue? I recall that one shows as B&W when you attempt to view it on a TV of the opposite type.

But I may be way off base here.

Thanks for the reply, but I tried that already. It switches between the two but the roll continues regardless. It stays in b/w as well when I switch between them. So I guess that's out.

Nothing on the inside looks fried and none of the connections are loose. I'm stumped but that's to be expected since I don't completely know what I'm doing yet.

 

[Resqueline]

What kind of cable do you use to the tv/monitor?

 

[Cubbie]

What kind of cable do you use to the tv/monitor?

Back when I used it before, I always used RCA cables. Since I've been trying to figure out the problem I've used the same RCAs, different RCAs, S-Video, and component cables. I've also tried hooking it up to a different tv and running it through a vcr. All with the same results.

 

[Resqueline]

Baffling problem, I'm lost.. You seem to have tried it all. I had initially thought it was a PAL-NTSC compatibility issue. I guess all that's left is a weird fault in the DVD player.
I'd not have much hope of fixing it short of obtaining & replacing a complex smd chip. Did you try to Google the model number to see if others have had the same problem?

 

[(*steve*)]

I wonder if there is a possibility of having a fault that causes disruption to the vertical sync.

Since the vertical sync is close to mains frequency, ripple on the DC rails *might* affect the creation of these pulses -- however I'm not sure that this would affect other than a modulated output.

Did this device operate for a long time without fault? Was it left powered on for a *long* time? Does it get warm when turned on? Could it be the slow death of filter capacitors?

I ask this because I have yet another device in front of me that has exactly that fault (death of capacitors, not rolling B/W image).

 

[Cubbie]

I'd not have much hope of fixing it short of obtaining & replacing a complex smd chip. Did you try to Google the model number to see if others have had the same problem?

I haven't Googled the specific model number yet. I've seen a few pages discussing fixes for similar problems, but I've tried all the things they've suggested and of course nothing worked. I'm starting the think it's the kind of thing I'd have to spend money on and that's not really my objective on this one.

Did this device operate for a long time without fault? Was it left powered on for a *long* time? Does it get warm when turned on? Could it be the slow death of filter capacitors?

I ask this because I have yet another device in front of me that has exactly that fault (death of capacitors, not rolling B/W image).

Yeah, I used it for a little while. My parents gave it to me when my real dvd player died and I used it till I was able to get another proper one. It wasn't left on for a long time and I haven't noticed it getting hot. But then since the problem started I haven't had it on for long at a time. When I get back home I'll try turning it on for a while to see if it heats up.


Thanks for the suggestions everybody. We might just figure this thing out yet.