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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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squished vertical in Sharp 3LS36 color TV
I need help fixing the squished vertical in my Sharp 3LS36 TV. This is a
mini color set from 1986. You can view the symptom at: http://antiqueradio.org/art/temp/Sharp3LS36Screen.jpg A piece of the schematic showing the vertical circuits is at: http://antiqueradio.org/art/temp/Sharp3LS36sch1.jpg I have replaced C501, C502, and C503. I measure 9.4vdc at pin 14 of the IC, as spec'd. At pin 13 next door, however, I measure close to zero, rather than the 6.8vdc called for. Ideas? This kind of project is a little beyond me. I can fix old tube radios, but don't have solid-state expertise or equipment. So any hints would be much appreciated. Thanks! Phil Nelson |
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Can be C509, 502, 506, 503. These are very likely to give this type of fault. Use an ESR meter to properly check the caps, or change them. -- Jerry G. ====== "Phil Nelson" wrote in message link.net... I need help fixing the squished vertical in my Sharp 3LS36 TV. This is a mini color set from 1986. You can view the symptom at: http://antiqueradio.org/art/temp/Sharp3LS36Screen.jpg A piece of the schematic showing the vertical circuits is at: http://antiqueradio.org/art/temp/Sharp3LS36sch1.jpg I have replaced C501, C502, and C503. I measure 9.4vdc at pin 14 of the IC, as spec'd. At pin 13 next door, however, I measure close to zero, rather than the 6.8vdc called for. Ideas? This kind of project is a little beyond me. I can fix old tube radios, but don't have solid-state expertise or equipment. So any hints would be much appreciated. Thanks! Phil Nelson |
#3
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You have to be willing to replace capacitors . Read posts on antique
radio :-) |
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"Phil Nelson" wrote in message hlink.net...
I need help fixing the squished vertical in my Sharp 3LS36 TV. This is a mini color set from 1986. You can view the symptom at: http://antiqueradio.org/art/temp/Sharp3LS36Screen.jpg A piece of the schematic showing the vertical circuits is at: http://antiqueradio.org/art/temp/Sharp3LS36sch1.jpg I have replaced C501, C502, and C503. I measure 9.4vdc at pin 14 of the IC, as spec'd. At pin 13 next door, however, I measure close to zero, rather than the 6.8vdc called for. Ideas? This kind of project is a little beyond me. I can fix old tube radios, but don't have solid-state expertise or equipment. So any hints would be much appreciated. Thanks! Phil Nelson This is a fairly straightforward push-pull output, like the audio output stage of a cheap radio. Do you have a scope and any sample waveforms? I would be suspicious of C509, it is in the return path to ground of the vertical yoke. H. R.(Bob) Hofmann |
#5
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Can be C509, 502, 506, 503. These are very likely to give this type of
fault. Forgot to mention that I already changed C509 (as well as 501, 502, 503 as mentioned in original post). Haven't tried 506 yet, though. Thanks! Phil |
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On Wed, 10 Nov 2004 18:55:54 GMT, "Phil Nelson"
put finger to keyboard and composed: I need help fixing the squished vertical in my Sharp 3LS36 TV. This is a mini color set from 1986. You can view the symptom at: http://antiqueradio.org/art/temp/Sharp3LS36Screen.jpg A piece of the schematic showing the vertical circuits is at: http://antiqueradio.org/art/temp/Sharp3LS36sch1.jpg I have replaced C501, C502, and C503. I measure 9.4vdc at pin 14 of the IC, as spec'd. At pin 13 next door, however, I measure close to zero, rather than the 6.8vdc called for. I'm betting that C509 has dried out. I'd change C506 as well. Vertical size appears to be regulated by sensing the voltage across a 2 ohm resistor. The current through this resistor is the vertical yoke current. Pin 15 of the IC is the feedback pin. - Franc Zabkar -- Please remove one 's' from my address when replying by email. |
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"Franc Zabkar" wrote in message
... I'm betting that C509 has dried out. I'd change C506 as well. Replaced C509 and C506. Still no improvement. Vertical size appears to be regulated by sensing the voltage across a 2 ohm resistor. Do you mean the 2 ohm resistor that looks like it's in package (M601) along with a 820 ohm resistor ? Thanks! Phil |
#8
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Phil,
Unsavory as it sounds, you may have a shorted turn in the yoke vertical winding, as process of elimination narrows down the possible culprit. Bill(oc) |
#9
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Ouch. Dare I ask how a numbskull like me might test for that condition?
Regards, Phil "Bill Sheppard" wrote in message ... Phil, Unsavory as it sounds, you may have a shorted turn in the yoke vertical winding, as process of elimination narrows down the possible culprit. Bill(oc) |
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