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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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Zenith Z35X21D Power Supply
This set came in with a blown fuse and a badly burned RX3406. QX3401 was
also shorted, but nothing else appeared out of order. I replaced the transistors with an NTE type, and took a guess on the value of the resistor, using a 4.7 ohm fusible. Got nothing but a puff of smoke when I plugged it in. Redid the power supply but used a 47 ohm resistor instead, with the same results. It appears that the power supply simply will not oscillate, and is instead trying to feed pure DC into the switching transformer resulting in the shorted condition. I also tried replacing the switching regulator STR53041, with no luck. There are no shorts on the secondary side of the power supply (HOT and everything is good) so I know the trouble has to be the power supply itself. Can anyone provide me with the correct value of RX3406? Also, is it critical that QX3401 be replaced with an exact part # (2N4923)? I should also point out that the two small 'lytics in the supply were checked, one was replaced. Any help would be much appreciated. |
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