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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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Strange Design of Hitachi TV
Forget the exact model number, it was a 14" set mfd around Dec. '86. This
was the first such model I've worked on, and this one had a bad flyback. Once the replacement was installed, the set ran but had a strange bluish haze (with retrace lines) only in the center of the screen. After ruling out any shorts in the CRT or supply voltage problems (cathode supply etc) I noted that the original flyback had a strange feature - the focus and screen wires were integrated into one coax-like cable. The focus was in the center, and the screen was on the shielding. Wondering if this had something to do with it, I took a long piece of thin wire and wrapped it around the full length of the new focus and screen wires (together) and connected this wire to the CRT ground. Success! Anyone care to explain what was going on here? I've never seen anything like it before...... |
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Spulerious signal suppression, something was radiating off the focus or
screen lines and was being picked up possibly by the video leads running to the crt board from the chassis. Seen lines and ramdom noise radiated into the video in other designs, sometimes just relocating video leads from the chassis to the crt pcb will suffice. "Chris F." wrote in message ... Forget the exact model number, it was a 14" set mfd around Dec. '86. This was the first such model I've worked on, and this one had a bad flyback. Once the replacement was installed, the set ran but had a strange bluish haze (with retrace lines) only in the center of the screen. After ruling out any shorts in the CRT or supply voltage problems (cathode supply etc) I noted that the original flyback had a strange feature - the focus and screen wires were integrated into one coax-like cable. The focus was in the center, and the screen was on the shielding. Wondering if this had something to do with it, I took a long piece of thin wire and wrapped it around the full length of the new focus and screen wires (together) and connected this wire to the CRT ground. Success! Anyone care to explain what was going on here? I've never seen anything like it before...... |
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