[MrCrabs]

I just got an old old old old NEC RPTV. It is a DT-3462S circa 1989. It is a 43" 4:3 screen. The picture is decent considering the age of the set, the size is a nice step up from my 26" standard def crt set.


I turned the set on and the picture was slightly blurry for about 10-15 minutes. It got somewhat better on its own, then I attempted to adjust the convergence using the front dials. I was able to get the red spot on (in the center, not 100% sure about the edges) The blue horizontal control was maxing out but was still not centered with the green and red.

The picture was decent at this point, and I left a movie playing while starting doing research. After 2 hours the picture was out of focus.


I have the service manual and did some adjustments to attempt to fix the focus and convergence issues (on the Dynamic Conv PCB). I ended up with the reg and green focus adjustment pots maxed out, and the horizontal width pot is set to the minimum. The picture was better and I was able to get the all 3 colors converged.


The picture stayed ok for a while, however the set is now doing something weird. I think the overscan is pretty high, I can only see 1/3 of the Comedy Central logo in the lower right corner, and the bottom of the logo is cut off. When the rating comes up in the top left corner, I can only see the bottom 1/3 of it, and only the right half.

The set will zoom in and out at times, it happens mostly at a scene change, where it goes from a picture to black, then back to an image. When zoomed out most of the image is seen, but it quickly zooms back in.

Just now I have been playing with the brightness and picture controls, and it seems like the brightness of the image being shown affects the amount of overscan. Maybe tomorrow I will pause a DVD and see if I can confirm the overall brightness is changing the overscan %.


Any idea what could be causing this behavior?


Before I spend time or money trying to focus the tubes and get the convergence set, I want to make sure the set is going to last. I didn't notice this overscan/zooming change problem before I made adjustments to the Dynamic Conv PCB, could I have caused this by having some of the trim pots maxed out?



Another question about this set, it seems like the only way to get at the tubes is to pull the mirror off.... So if I pull the mirror off, how the heck do I try and focus/align the tubes? Anyone remember working on one of these?


Thanks in advance for answers.

 

[MrCrabs]

So I did some more messing around last night.

I took the front grill and speakers out, and that is how you access the tubes.

In the back there is a metal panel covering the lenses and it looks like if I take that off I can get access to the lenses.


I also realized I can pull the Dynamic Convergence PCB out thru the front of the set, and watch the picture while I make adjustments... (instead of having the wife try and help) I was able to get the red and green almost 100% converged but the blue is having issues.

The green and blue are also out of focus, but the red looks good.


I discovered the glue holding the focus and CPC magnets in place has dried up over 20 years, and almost all the magnets are loose. I found a focus thread (avsforum . com/avs-vb/showthread.php?t=98042) with some great instructions by Guy Kuo. I plan to read that several times and attempt to do a complete overhaul including mechanical centering, lens flapping, optical focus, electronic focus and convergence.


The set may have some issues with the blue convergence circuits, and possibly the horizontal width controls. But its hard to pinpoint anything with a slightly blury image. The blue CPC magnets were the worst in terms of looseness so I hope once I get the tubes all setup properly I can nail down the convergence issues with the blue.


For test patterns I was thinking of making up my on jpg images in 640x480 resolution and burning them to a cd/dvd and using my DVD player to display the images, since this is a standard def 480i set would that be the proper resolution to use?



Any advice for a beginner trying to do this?


I did send emails to the local home theater shops which were listed on the ISF website, but haven't heard anything back yet. Maybe I will try calling them, but since the TV was free the accountant (the wife) doesn't think spending money on it is worth it...


Anyone in the Western NY area that would be able/willing to help me out? I could probably afford gas money, and provide food/snacks/beer/pop while we work, maybe even a modest fee.