1. Home
  2. Electronics Repair
  3. Proscan PS56670 convergence

Proscan PS56670 convergence

So I just bought a used Proscan 56" projection TV (PTK195 Chassiso or CTC195). It intermittently has a strange convergence problems. The image will get bad pincushion on all 4 sides and the colors will not be lined up. The problem can be fixed by going in the Menu->Screen->Correct Image (I think)-> then selecting whatever it detected is wrong. It can also usually be fixed by turning the power off for a second. But once it starts happening it will tend to return about every 1 to 3 minutes, sometimes more sometimes less. I didn't notice this problem when I looked at it before buying, OTOH didn't have it until the second time I used it after I got it home. Any ideas what could be causing this problem?

BTW when I moved it I hauled it in my pickup lying diagonally in the back, screen up, on a bunch of foam padding. I was a bit concerned about road vibration but it was not too bad.

W
Reply to
hikinandbikin
Loading thread data ...

I guess you bought it from a private owner? I can't tell you how many people buy used big screens with intermittent problems. The original owners know there's a problem, and unload them for what they can get.

Anyway, the 195 series uses a seperate power supply just for the convergence amplifiers, and will shut down for excessive current leaving a misconverged and distorted picture. Sometimes these supplies shutdown for no reason, and the supply must be repaired. Other times, it detects an overcurrent on the plus/minus 34volt line, and shuts down.

If the supply isn't shutting down, it could be a problem with communication from the main chassis to the convergence chassis, or a problem in the convergence correction waveform generator section.

It will be easier to diagnoss this when the convergence fails completely.

John

Reply to
John-Del

So a little update. Last night the problem was occurring every few minutes immediately after I powered on the TV. Well, in the process of looking for all of the SN and chassis data I decided it would be smart to unplug it for while. When I plugged it back in I didn't try to power it back on as I was headed up to post this problem. But I did make an observation at the time. When I got the set and first plugged it in I noticed it made a little bit of sound (kind of a hum), presumably from the power supply. It continued to make this noise until I unplugged it. But, When I plugged it back in the noise never restarted. This morning I ran the TV for about an hour with no problems. Could it be that this was all a digital fluke with some memory location that cleared with power, or is it more likely that an hour was not long enough to manifest? Notably last night my roomate had watched tv for 2 hours and only had a couple problems. He turned it off, then half hour later I turned on and the frequent problems started.

Also where do I get a service manual? All I found on RCAs website was the owners manual. What about system schematics. I would rather avoid spending a couple hundred dollars on manuals from thomsonnetwork.com.

Hopefully this is useful info.

Reply to
hikinandbikin

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.