Home |
Search |
Today's Posts |
|
Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
Reply |
|
LinkBack | Thread Tools | Display Modes |
#1
|
|||
|
|||
Please help in identifying TV picture fault.
Hello,
Before I get the Tech in, was wondering if anybody has any insight as to what this problem may be.. My 1992 Sony kv27xbr35 has developed an unusual picture problem. It's intermittent, sometimes it's not there at all, the rest of the time it varies in intensity, seems worse on a bright dynamic picture where the contrast is higher. It's basically alternating light and dark horizontal lines, about 1/2 wide (approx) which seem to shimmer. Here's a sample: http://home.comcast.net/~davetest/capture.mpg (370kb) Please note: the rainbow/diagonal effect is not a part of the problem, but an artifact produced during the HI8 capture. This fault appears regardless of the source, just as likely to be dvd player, vcr or DBS. Does it through the RF and video/s-video inputs. Appreciate any feedback. Dave |
#2
|
|||
|
|||
Sounds as if the crt may be getting weak and the AKB circuit can no longer
keep up with the beam current demands. Is the symptom worse if the contrast and brightness are at a higher than mid range setting and go away when both settings are set quite a bit lower? If so then you either have a soft crt or something in the bias circuitry to the crt going awry. "davexnet02" wrote in message ... Hello, Before I get the Tech in, was wondering if anybody has any insight as to what this problem may be.. My 1992 Sony kv27xbr35 has developed an unusual picture problem. It's intermittent, sometimes it's not there at all, the rest of the time it varies in intensity, seems worse on a bright dynamic picture where the contrast is higher. It's basically alternating light and dark horizontal lines, about 1/2 wide (approx) which seem to shimmer. Here's a sample: http://home.comcast.net/~davetest/capture.mpg (370kb) Please note: the rainbow/diagonal effect is not a part of the problem, but an artifact produced during the HI8 capture. This fault appears regardless of the source, just as likely to be dvd player, vcr or DBS. Does it through the RF and video/s-video inputs. Appreciate any feedback. Dave |
#3
|
|||
|
|||
On Fri, 24 Sep 2004 04:27:07 -0400, "Art"
wrote: Sounds as if the crt may be getting weak and the AKB circuit can no longer keep up with the beam current demands. Is the symptom worse if the contrast and brightness are at a higher than mid range setting and go away when both settings are set quite a bit lower? If so then you either have a soft crt or something in the bias circuitry to the crt going awry. The distortion in the picture is intermittent. I tried to produce an mpeg of the problem. It's similar, but it doesn't do it justice due to the limitation of the HI8 recording. The distortion on the TV is shimmering horizontal lines, half an inch wide, no tearing, no rainbow colors, no diagonal patterns. It seems that when the "picture" control is turned down it fades a little. I eyeballed the screen up close and in the dark stripes, it seems as if every other line in there is unlit. ie. it's pure black on the screen. Dave |
#4
|
|||
|
|||
The only way that the tech is going to know what the brightness fault
is, he is going to have to check the G2 bias, and the biases to the CRT. It is possible to have a bias fault to the CRT, a supply fault from the G2 supply, general power supply faults, or a bad CRT to cause brightness variations. -- Jerry G. ====== "davexnet02" wrote in message ... Hello, Before I get the Tech in, was wondering if anybody has any insight as to what this problem may be.. My 1992 Sony kv27xbr35 has developed an unusual picture problem. It's intermittent, sometimes it's not there at all, the rest of the time it varies in intensity, seems worse on a bright dynamic picture where the contrast is higher. It's basically alternating light and dark horizontal lines, about 1/2 wide (approx) which seem to shimmer. Here's a sample: http://home.comcast.net/~davetest/capture.mpg (370kb) Please note: the rainbow/diagonal effect is not a part of the problem, but an artifact produced during the HI8 capture. This fault appears regardless of the source, just as likely to be dvd player, vcr or DBS. Does it through the RF and video/s-video inputs. Appreciate any feedback. Dave |
#5
|
|||
|
|||
On Fri, 24 Sep 2004 16:20:57 -0400, "Jerry G."
wrote: The only way that the tech is going to know what the brightness fault is, he is going to have to check the G2 bias, and the biases to the CRT. It is possible to have a bias fault to the CRT, a supply fault from the G2 supply, general power supply faults, or a bad CRT to cause brightness variations. Thanks Jerry, oddly enough the tech just rebuilt the power supply. 2 leaky diodes, 2 35v capacitors and a drive transformer. To be fair to him, I had seen this once or twice before, it was very low intensity, and it came and went. But since the PS was fixed, it's back, and it's much more vivid. The tech came to the house, and off the top of his head didn't know what it was. He asked me to leave it for a week or two to see if anything changes, and to give him time to think about it. Dave |
#6
|
|||
|
|||
Don't know how relavent this is, but a similar problem I found in a Mitsubishi
Projection unit was traced to a bad cap in the power supply |
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Sony KV-32S40 has audio but no picture | Electronics Repair | |||
Semi OT Electrical Question | Woodworking | |||
No picture but sound on SONY KV-35V36 | Electronics Repair |