Samsung Projection HDTV Convergence Problems
 

This Samsumg set is clearly not going to be an easy fix. It came in with
severe convergence problems - no two colors converged properly at any point
on the screen. I started by checking the two large convergence IC's
(STK392-010); both had the correct supply voltages, but two of the three
sections on one IC were not functioning at all (input present but no output)
so I assumed the IC was bad. For good measure, I replaced both IC's. Once
powered up, the picture was still severely distorted but this time, ICZ103
(which was formerly bad) now overheats severely. So I tried disconnecting
the output leads from that IC, and it now runs cold - but of course the
picture is still distorted.
At this point I suspect an underlying fault somewhere else, putting an
excessive load on the IC and causing it to fail. I checked the three yokes
and all measure the exact same impedance, ruling out the possibility of a
shorted yoke. Because of the complexity of this set, it would be pointless
to venture any deeper without the aid of a service manual, or at least some
advice as to what the problem might be.
Thanks for any advice.

Samsung Projection HDTV Convergence Problems
 

May I ask a stupid question? Is there any possibility the "display elements"
(tubes, LCD panels, whatever) are themselves misaligned? I assume they would
be mounted and locked into a rigid frame, but... Is there any chance the
owner is a screwdriver mechanic, and that a minor convergence problem
tempted him into going where homo vulgaris is not supposed to tread?

Samsung Projection HDTV Convergence Problems
 

There's no evidence that the static alignment was tampered with, or that the
set was ever dropped etc. I will do some more checking and let you know.

"Meat Plow" wrote in message
...
On Sat, 31 Oct 2009 11:09:48 -0700, "Chris F."
wrote:

This Samsumg set is clearly not going to be an easy fix. It came in with
severe convergence problems - no two colors converged properly at any
point
on the screen. I started by checking the two large convergence IC's
(STK392-010); both had the correct supply voltages, but two of the three
sections on one IC were not functioning at all (input present but no
output)
so I assumed the IC was bad. For good measure, I replaced both IC's. Once
powered up, the picture was still severely distorted but this time, ICZ103
(which was formerly bad) now overheats severely. So I tried disconnecting
the output leads from that IC, and it now runs cold - but of course the
picture is still distorted.
At this point I suspect an underlying fault somewhere else, putting an
excessive load on the IC and causing it to fail. I checked the three yokes
and all measure the exact same impedance, ruling out the possibility of a
shorted yoke. Because of the complexity of this set, it would be pointless
to venture any deeper without the aid of a service manual, or at least
some
advice as to what the problem might be.
Thanks for any advice.


Check the static alignment and check around the STK devices for open
low value, low wattage resistors (10 ohm 1/10 watt). Samsung were
notorious for chewing up convergence amps and surrounding components.

The convergence amps didn't need a special reason to fail other than
after time not being sufficiently torqued to the heatsink.

Samsung Projection HDTV Convergence Problems
 

"Chris F." wrote in message
...
This Samsumg set is clearly not going to be an easy fix. It came in with
severe convergence problems - no two colors converged properly at any
point on the screen. I started by checking the two large convergence IC's
(STK392-010); both had the correct supply voltages, but two of the three
sections on one IC were not functioning at all (input present but no
output) so I assumed the IC was bad. For good measure, I replaced both
IC's. Once powered up, the picture was still severely distorted but this
time, ICZ103 (which was formerly bad) now overheats severely. So I tried
disconnecting the output leads from that IC, and it now runs cold - but of
course the picture is still distorted.
At this point I suspect an underlying fault somewhere else, putting an
excessive load on the IC and causing it to fail. I checked the three yokes
and all measure the exact same impedance, ruling out the possibility of a
shorted yoke. Because of the complexity of this set, it would be pointless
to venture any deeper without the aid of a service manual, or at least
some advice as to what the problem might be.
Thanks for any advice.



Disconnecting the output leads (presuming you mean the leads to the yokes)
should not make the ICs run cold. Running them unloaded will usually cause
overheating in the output resistors in the circuit. You may have
disconnected the supply to the ICs.

If you are getting correction from the DCU to the inputs of the output ICs,
you probably missed something like an open resistor on the output stage.
You may have blown a chip or a supply fuse.

Leonard