This is one of my first real attempts at a diy amplifier.
I assembled this earlier today as shown with 6800uF 56V capacitors and 500ohm 3 watt resistors. I powered it up with no load and the resistor on the negative rail burned. I am guessing.... Without a load, the current flowed through the resistor. Can this type of PSU not be powered without a load? Were the resistors not enough wattage? Were the capacitors too low of a rating? Should I have fuses in series on the two feeds from the transformer?
I assembled this earlier today as shown with 6800uF 56V capacitors and 500ohm 3 watt resistors. I powered it up with no load and the resistor on the negative rail burned. I am guessing.... Without a load, the current flowed through the resistor. Can this type of PSU not be powered without a load? Were the resistors not enough wattage? Were the capacitors too low of a rating? Should I have fuses in series on the two feeds from the transformer?
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What is the Vcc value?
Current flows through the resistors loaded or unloaded. If one burned, there must be a design or build issue.
Current flows through the resistors loaded or unloaded. If one burned, there must be a design or build issue.
The transformer is 35-0-35. The capacitors came out of a bad receiver. Is it posible that they are at fault? Should the capacitors be rated over the full voltage or the rail voltage? Where should fuses be located?
So the Vcc value is ~48V?
Ohm's law to the rescue. If there are 48 volts across 500 ohms, nearly 100 milliamps will flow through the resistor (48/500=0.096). Power is voltage times amperage so 48*0.096=4.608. Your circuit puts about 4.5 watts into a 3 watt resistor.
The capacitors' WVDC should be fine - there's 10+% margin there, though some may prefer it closer to 20%. The transformer should be fused on the primary side.
Ohm's law to the rescue. If there are 48 volts across 500 ohms, nearly 100 milliamps will flow through the resistor (48/500=0.096). Power is voltage times amperage so 48*0.096=4.608. Your circuit puts about 4.5 watts into a 3 watt resistor.
was the correct question.
The capacitors' WVDC should be fine - there's 10+% margin there, though some may prefer it closer to 20%. The transformer should be fused on the primary side.
OK> This is beginning to come together for me. As an automotive technician, Ohms law gets ignored quite a bit. A lot of guessing based on experience. In school were taught to use ohms law to zero in on almost anything from 5 feet down a wire. In the field it gets thrown to the wayside. Thanks for the refresher and for giving me back some fundatmentals that I will hold on to. I googled Vcc and did not find it. What exactly is Vcc and how is it calculated?
I understand. Ohm's law is useful enough that it's best to hold it close so it only burns you when it isn't accurate.🙂
Vcc is the label for the outputs on your power supply. It isn't calculated as much as just determined from the particular circuit. I don't remember exactly, but I believe the term arose as symbolizing the collector voltage on a transistor. It's use spread to include any general supply voltage, whether BJTs were included in the circuit or not.
Vcc is the label for the outputs on your power supply. It isn't calculated as much as just determined from the particular circuit. I don't remember exactly, but I believe the term arose as symbolizing the collector voltage on a transistor. It's use spread to include any general supply voltage, whether BJTs were included in the circuit or not.
The problem isn't why did a resistor burn, but why did only one burn: they are in the same boat, and should behave identically
The only thing that could be wrong here is that a capacitor could be leaking. I had a receiver that was going into overload. The previous technician snipped all of the output modules searching for a problem. I was curious about the 6800uF capacitors because there was a very slight bulge on them. At $14 per output module I decided to scrap the $30 receiver. I salvaged the suspicious Capacitors without testing. How do I test capacitiors? What do I need? Capacitance tester and ESR tester?
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