My Sony CRT TV Model KV-M1420U has developed a problem. After 15 minutes
of perfect picture, the picture fades out by going through a colour change
to purple then totally black. All channels are affected. Switching off
for a few minutes recovers the picture but the situation repeats.

Anyone one got an idea where I should start to look for this thermal
problem? I am trained and familiar with working with high voltage and
electronic circuits but I'm not a T.V. engineer.

Beemer

"Beemer" wrote in message
k...
My Sony CRT TV Model KV-M1420U has developed a problem. After 15 minutes
of perfect picture, the picture fades out by going through a colour
change
to purple then totally black. All channels are affected. Switching off
for a few minutes recovers the picture but the situation repeats.

Anyone one got an idea where I should start to look for this thermal
problem? I am trained and familiar with working with high voltage and
electronic circuits but I'm not a T.V. engineer.

Beemer



Perhaps the CRT filament voltage dies off?

Mark Z.

"Mark D. Zacharias" wrote in message
et...
|
| "Beemer" wrote in message
| k...
| My Sony CRT TV Model KV-M1420U has developed a problem. After 15
minutes
| of perfect picture, the picture fades out by going through a colour
| change
| to purple then totally black. All channels are affected. Switching
off
| for a few minutes recovers the picture but the situation repeats.
|
| Anyone one got an idea where I should start to look for this thermal
| problem? I am trained and familiar with working with high voltage and
| electronic circuits but I'm not a T.V. engineer.
|
| Beemer
|
|
|
| Perhaps the CRT filament voltage dies off?
|
| Mark Z.
|
|
|
Mark,

Only guessing but is there a heater for each primary or is a common heater
normally used?

Would the heater voltage be around 12V?

Beemer

On 3 ago, 01:29, "Beemer" wrote:
My Sony CRT TV Model KV-M1420U has developed a problem. After 15 minutes
of perfect picture, the picture fades out by going through a colour change
to purple then totally black. All channels are affected.
Beemer

this sounds like a dry joint - probably in the heater line- first
check the little board attached to the CRT.
Sonys especially tend to develop lots of dry joints, so you'd be well
advised to take out the main board and inspect underneath,
resoldering anything suspicious. You may even avoid expensive problems
ocurring if you're careful.

-B

"b" wrote in message
ups.com...
| On 3 ago, 01:29, "Beemer" wrote:
| My Sony CRT TV Model KV-M1420U has developed a problem. After 15
minutes
| of perfect picture, the picture fades out by going through a colour
change
| to purple then totally black. All channels are affected.
| Beemer
|
| this sounds like a dry joint - probably in the heater line- first
| check the little board attached to the CRT.
| Sonys especially tend to develop lots of dry joints, so you'd be well
| advised to take out the main board and inspect underneath,
| resoldering anything suspicious. You may even avoid expensive problems
| ocurring if you're careful.
|
| -B
|
|
B,

If it is a dry joint I assume that it is expansion which results in the
failure. Would using a cold spray be appropriate to try to isolate the
failing component? I would normally only use a spray on on an
semiconductor.

Beemer

Beemer ha escrito:
If it is a dry joint I assume that it is expansion which results in the
failure. Would using a cold spray be appropriate to try to isolate the
failing component? I would normally only use a spray on on an
semiconductor.

Beemer

just look for cracked solder on the crt board and near the line
transformer (the big 'un).
-B

On 4 Aug, 04:14, b wrote:
Beemer ha escrito:

If it is a dry joint I assume that it is expansion which results in the
failure. Would using a cold spray be appropriate to try to isolate the
failing component? I would normally only use a spray on on an
semiconductor.

Beemer

just look for cracked solder on the crt board and near the line
transformer (the big 'un).
-B

best way to find bad joints IME is to tap gently with an insulating
rod.


NT