I found that the rectifier + fuse resistor + another transistor were fried, and i replaced them. But still can't get it to work.
GENERALLY SPEAKING about power supplies, Did you use exact replacement parts or parts of equivalent values? Not all electronic parts are created equal. For example, basically, transistors, for the sake of this discussion, come in two types. NPN and PNP. The 3 contacts on them are the emitter, base and collector. If it is a PNP type, the emitter will be the positive input, the base will be the negative leading control pin and the collector will be the positive output. If it is an NPN type, these pin functions will be the same but with the polarities reversed. There are small transistors that operate at the milliamp level and there are large ones that control hundreds of amps and everything in between. You can replace either transistor with one of higher capacity as long as it's gain rating at the base connection is the same. If your original transistor was a PNP type, had an emitter voltage of 25 volts, a collector current rated at 3 amps and a base gain of 20, you could replace it with one rated at 50 volts, a gain of 20 and a current rating of 5 amps AS LONG AS it is still a PNP. Another consideration is that transistors that look identical can have differing pin configurations. Yours could have been EBC from left to right but the replacement that I suggested could be CBE , BEC or ECB. This part can still work if you can bend the leads around to reach the correct holes WITHOUT shorting to each other. If you have the wrong pins in the wrong holes or the right pins in the right hols but using an NPN in place of a PNP or PNP in place of an NPN, or if you install the correct transistor backwards, again, no joy.
Now there are 2 types of diodes in power supplies. There are rectifier diodes which have 2 pins. The anode and cathode. The anode is the positive input and the cathode is the output. ALL diodes, regardless of type pass power in only one direction. Depending on how the power supply was designed, it can use 2 or 4 diodes. You can also find rectifier bridges containing 4 diodes in one package that will look like a square plastic block, an integrated circuit standing on it's 4 pins or it can contain 2 diodes and look like a 3 pin power transistor. Any of these take the AC power out of a step down transformer or even directly off from the mains and convert it to a pulsating DC current. You can replace a rectifier bridge with 4 discrete diodes or vise versa AS LONG AS their voltage and current ratings are the same or higher and if there is no need for a heat dissipation device. If you install a single diode backwards, you won't get the correct voltage. If you connect a diode bridge wrong, it won't work at all. Then there is a beast called a ZENER diode. These also have rated voltages and currents like regular diodes but for a different reason. These are installed into a different section of the power supply and act as a voltage regulator. If you are working with these, you MUST replace it with the EXACT same unit. If you replace it with a unit rated at a higher voltage, yous power supply will output a higher voltage. Conversely, if you replace it with one of a lower voltage, your output will be lower. This could either damage what you are running off from this supply or the voltage will be so low that it won't function properly or at all. Their use is waning in favor of IC regulators except for extremely specialized circuits as they can produce radio noise that may be unwanted or disruptive. If you install one of these backwards in a circuit, it won't work either. Resistors are pretty self explanatory as long as you use ones of the same resistance and at least of the same wattage rating. You can increase the wattage but the resistance must remain unchanged. Good luck.
Testimonial: "Thank you for your answer Jeff, indeed I used replacement parts identical to the original ones. I think there is something else that needs replacing but I am unable to figure it out. I thought maybe it's possible to upload some pictures and get some guidance on the points that I can check on the power circuit, but i cannot see an option here. Thanks Motti"
Thank you for your answer Jeff,
indeed I used replacement parts identical to the original ones. I think there is something else that needs replacing but I am unable to figure it out. I thought maybe it's possible to upload some pictures and get some guidance on the points that I can check on the power circuit, but i cannot see an option here.
Thanks, Motti
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SOURCE: Reads PROTECT on the display of my Onkyo TX-SV525 ???
HOWDY, NOW YOU COULD TRY THIS ONE: POWER THE RECEIVER UP , THEN PUSH&HOLD !THE VIDEO 1 BUTTON, THEN TURN THE PIECE IN THE OFF (STANDBY MODE ) ,IT WILL SAY "CLEAR SO IT SHOULD BE BACK TO IT,S ORIGINAL FACTORY SPECIFICATION,S. SUCCES ! AMSTERDAMCOWBOY-HOLLAND-NOW FLORIDA! 4-EVER
SOURCE: sharp TV 21" screen with a switch mode power supply.
i have a tv receiver with a problem of no power going to the whole system thiis transistor c3807 and connected to bigger transistor c4458 are gone together with connecting diodes.any solution please?
SOURCE: blower motor resistor overheats and fried connector to blower
You should be replacing the blower motor with the resistors. If your buying the parts from the dealer an experienced parts person will insist you replace both at the same time. The blower motor is usually what burns out the resistors.
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