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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. |
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#1
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Can someone identify this NTSC video (CRT) monitor problem? Is itsimple?
Hello all.. I have a monitor that allows viewing of the retrace and
overscan periods, so I somewhat fond of it. However, it consistently displays this symptom: http://www.bobdbob.com/~deneb/ftp/monitor.jpg The scan lines are disordered near the top of the image. The display is usually static, but with certain images, some of the lines jump around a little. The rest of the image is fine and all the controls work as expected. Is there a common cause for this? If so, is it easy to fix, or should I junk it and focus on remembering the good times? |
#2
Posted to sci.electronics.repair
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Can someone identify this NTSC video (CRT) monitor problem? Is itsimple?
Hello all.. I have a monitor that allows viewing of the retrace and
overscan periods, so I somewhat fond of it. However, it consistently displays this symptom: http://www.bobdbob.com/~deneb/ftp/monitor.jpg The scan lines are disordered near the top of the image. The display is usually static, but with certain images, some of the lines jump around a little. The rest of the image is fine and all the controls work as expected. Is there a common cause for this? If so, is it easy to fix, or should I junk it and focus on remembering the good times? This is likely a bad electrolytic in the field output circuit. Not a difficult repair. |
#3
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Can someone identify this NTSC video (CRT) monitor problem? Is itsimple?
By the way:
The model number is Panasonic BT-S1300N. If anyone has any service info and could give some hints I'd be very grateful. JP: I can see your point, I might be able to handle that job. I have bad luck with TV-type hardware for some reason. I've only ever succeeded in repairing one once. On Jan 9, 1:52*pm, Jeroni Paul wrote: Hello all.. I have a monitor that allows viewing of the retrace and overscan periods, so I somewhat fond of it. However, it consistently displays this symptom: http://www.bobdbob.com/~deneb/ftp/monitor.jpg |
#4
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Can someone identify this NTSC video (CRT) monitor problem? Is itsimple?
Very common, there are bad capacitors in the vertical deflection amplifier. There may be a number of these that have to be changed. They can be easily verified with an ESR meter. To service this, it is best to have experience in TV service. Jerry G.. -- On Jan 9, 10:08*am, " wrote: Hello all.. I have a monitor that allows viewing of the retrace and overscan periods, so I somewhat fond of it. However, it consistently displays this symptom: http://www.bobdbob.com/~deneb/ftp/monitor.jpg The scan lines are disordered near the top of the image. The display is usually static, but with certain images, some of the lines jump around a little. The rest of the image is fine and all the controls work as expected. Is there a common cause for this? If so, is it easy to fix, or should I junk it and focus on remembering the good times? |
#5
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Can someone identify this NTSC video (CRT) monitor problem? Is it simple?
On Fri, 9 Jan 2009 13:02:20 -0800 (PST), "
put finger to keyboard and composed: The model number is Panasonic BT-S1300N. If anyone has any service info and could give some hints I'd be very grateful. I'm not familiar with your monitor, but in general you would locate the 4-wire cable that connects to the deflection yoke around the picture tube. The two thinnest wires would connect to a vertical amplifier IC on the PCB. Since yours is a Panasonic monitor, I would expect that this IC would be made by Matsu****a and would have a part number beginning with AN. These ICs are often in a SIP package and are attached to a heatsink. Some designs use a pair of discrete transistors, also mounted on heatsinks. I'd replace all the electrolytic capacitors in the vicinity of this IC, and I'd also reflow its solder joints. - Franc Zabkar -- Please remove one 'i' from my address when replying by email. |
#6
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Can someone identify this NTSC video (CRT) monitor problem? Is itsimple?
Hello all.. I have a monitor that allows viewing of the retrace and
overscan periods, so I somewhat fond of it. However, it consistently displays this symptom: I've been going by the canonical repair faq.. and reading through it for the umpteenth time I discovered a mention of "vertical foldover." I hadn't seen that before. Is this what's going on in that photo? Also thank you F.Z., I probably can't screw it up with advice that clear. |
#7
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Can someone identify this NTSC video (CRT) monitor problem? Is it simple?
On Tue, 13 Jan 2009 10:02:33 -0800 (PST), "
put finger to keyboard and composed: Hello all.. I have a monitor that allows viewing of the retrace and overscan periods, so I somewhat fond of it. However, it consistently displays this symptom: I've been going by the canonical repair faq.. and reading through it for the umpteenth time I discovered a mention of "vertical foldover." I hadn't seen that before. Is this what's going on in that photo? That's one common symptom of bad caps, another is vertical non-linearity. You may also see retrace lines and/or digital teletext data (lines of dots) during the vertical retrace interval. If you can identify the vertical output IC, then you may find an application circuit in its datasheet. You can search for datasheets he http://www.datasheetarchive.com/ - Franc Zabkar -- Please remove one 'i' from my address when replying by email. |
#8
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Can someone identify this NTSC video (CRT) monitor problem? Is itsimple?
You were right, in case you had any doubt (which you probably did
not). It's an AN5512, and the cap between pins 4 and 8 of that chip had 90 ohms of series resistance and about 5% of it's labeled capacitance. I'm off to the local shop to get some electrolytics. On Jan 12, 6:07*pm, Franc Zabkar wrote: I'm not familiar with your monitor, but in general you would locate the 4-wire cable that connects to the deflection yoke around the picture tube. The two thinnest wires would connect to a vertical amplifier IC on the PCB. Since yours is a Panasonic monitor, I would expect that this IC would be made by Matsu****a and would have a part number beginning with AN. These ICs are often in a SIP package and are |
#9
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Can someone identify this NTSC video (CRT) monitor problem? Is itsimple?
Monitor's fixed. Thanks to everyone!
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#11
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Can someone identify this NTSC video (CRT) monitor problem? Is it simple?
On Fri, 16 Jan 2009 07:08:43 -0800 (PST), "
put finger to keyboard and composed: It's an AN5512, and the cap between pins 4 and 8 of that chip had 90 ohms of series resistance and about 5% of it's labeled capacitance. The sci.electronics.repair FAQ states that ... "[Vertical foldover] is probably caused by a fault in the flyback portion of the vertical deflection circuit - a charge pump that generates a high voltage spike to return the beam to the top of the screen." http://www.repairfaq.org/samnew/tvfaq/tvvfold.htm The cap between pins 4 and 8 of the AN5512 IC is indeed a "flyback" charge pump cap. See page 3 of the datasheet: http://www.datasheetarchive.com/pdf-...DSA-187661.pdf - Franc Zabkar -- Please remove one 'i' from my address when replying by email. |
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