Proscan PS56670 convergence

[hikinandbikin]

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

 

[Art]

Possible Deflection power supply problem or poor connections in the
deflection and convergence circuits. Will probably require some in-depth
diagnostics including checking the error codes. Since resetting the
registration via the menue the data is being compromised for some reason.
Time to get the service manua; and get into the item, posting results of
your diagnostics. Since it is intermittant it may take a bit of time to
track down.

 

[John-Del]

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

 

[hikinandbikin]

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.