Re: Cooler Master 550 watt - fan spins few seconds and then stop
Lets start at the beginning. Do you have 5 volts on the 5vsb output line?
everell
Badcaps Legend
Last Activity: 03-14-2024, 02:50 PM
Joined: 01-18-2009
Location: Williamsburg, Virginia
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Re: EVGA 500 watt with fan twitch
I was using a home made tester which had LEDs and there was a load resistor on the 3.3 volt line...which was obviously not correct. The cheap power supply testers you are referring to did a much better job than the one I was using. The real test is a dynamic test using a real mother board as a load. Both power supplies work ok using a real mother board. So the problem in both cases was a defective mag amp smt transistor marked M7A....Leave a comment:
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Re: EVGA 500 watt with fan twitch
Found another EVGA 500 watt power supply with same symptoms. Replaced the 3.3 volt mag amp smt transistor. Original was marked M7A. Replaced it with a 2F. Power supply now works OK. Not sure if this is a design problem or just OEM using a POS M7A smt transistor.Leave a comment:
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Re: EVGA 500 watt with fan twitch
I installed a Panjit transistor marked M7A. End result was the same....2.4 volts on the 3.3 volt line. I replaced the 431 regulator chip. No change. I removed the two output caps and tested for esr. Both OK. Totally frustrated, I finally changed the tester I was using. Now everything measures ok. So it looks like I was chasing a ghost!
Conclusions: EVGA 500 watt power supply had a bad mag amp smt transistor. The transistors marked M7A and 2F are apparently interchangeable. The power supply is now in my garage powering an old KT7A...Leave a comment:
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Re: EVGA 500 watt with fan twitch
I finally found MMBT2907A with M7A marking. It is made by Panjit. On Digikey and Mouser it is the cheapest MMBT2907A you can buy. Price is 8 cents apiece. What do you expect from a power supply made in China!Leave a comment:
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Re: EVGA 500 watt with fan twitch
My replacement MMBT2907A is marked 2F. I have checked the data sheet of several manufacturers and they all agree that the marking is 2F. Perhaps not all MMBT2907A transistors are equal???Leave a comment:
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EVGA 500 watt with fan twitch
This is an EVGA 500 watt Model 100-W1-0500. On power up only has a small fan twitch. Usually this is just a bad capacitor on one of the output lines. Not this time. I pulled out my storage scope and looked at the output lines during the first 10 msec after power up. 12 volt line was 11.5 volts. 5 volt line was 4.5 volts. But....the 3.3 volt line was also 4.5 volts. Couldn't find a short between the 5 volt line and the 3.3 volt line. So pulled out my multimeter and tried to find a bad component using resistance measurements. Nothing. So I took a guess that the mag-amp transistor might be bad. It... -
Re: Bestec ATX-250 12Z problems and solutions
Hello msb83,
Changing R59 and R60 to a potentiometer works well when trying to center the 5 volt output voltage. I don't think the power supply will allow you to get a range of 2 to 6 volts due to its design. The Bestec power supplies have some really good protection circuits (except for 5VSB on 12E model!) compared with the bargain basement cheapie power supplies.
I see that you are wanting to use this Bestec in an application involving a swimming pool. Personally I think this is an extremely dangerous situation....Leave a comment:
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Re: FSP150-50LG Fault
Whereas there has been no followup on this power supply, I hope you can bear with me with a little humor.
The picture here is a FSP power supply in which the 3.3 and 12v is "missing"!...Leave a comment:
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Hello master hoarder. I have too many power supplies in my attic as well as some mother boards and a dual trace scope. If you are willing to make a trip to Williamsburg, VA, I would love to meet you and share a lot of my stash. You can phone me or text me at (757)561-1118. everell -
Re: FSP150-50LG Fault
jarenfeldt: I know these posts so far have not been very helpful, but I was hoping to add a little humor to the repair process. Given enough time and money, any power supply can be fixed!
First, it would be more sociable to know what country, city, and state you are from.
Second, it would be most helpful to see some pictures of the power supply you are trying to repair.
And finally what information can you give as to what troubleshooting you have done. You mentioned, no 12 volts and no 3.3 volts. I would start by...Leave a comment:
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Re: FSP150-50LG Fault
The Bestec ATX250-12E is a great power supply IF you modify the 5VSB. The IMicro power supplies are also great power supplies IF you finish putting in all the parts that are supposed to be there. But the low power FSP power supplies are hard drive blowers. I have seen only one fix for them, as can be seen in the pictures. Not sure what size rifle bullet permanently fixed this hard drive blower....Leave a comment:
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Re: 7310/3510 supervisor chip with overcurrent protection
Here is a figure showing the waveforms I found on the Bestec ATX-400. On the left is what was on the 7510 chip and on the right what was on the outputs of the 12, 5, and 3.3 volt rails. The only difference was the waveform on pin 6 of the 7510 chip and the 5 volt rail. The voltage waveform tried to increase but shutdown in about 5 milliseconds. This time corresponds to one quarter of a sign wave at 60 hertz. This is the time it takes for the voltage to go from zero to maximum during one cycle. This is the amount of time required...Last edited by everell; 12-17-2020, 04:51 PM.Leave a comment:
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Re: 7310/3510 supervisor chip with overcurrent protection
Hello sam_sam_sam. Your comments/questions concerning a power supply using the PS223 chip shows the problem we are discussing. The PS223 chip has overvoltage/undervoltage protection AND overcurrent protection. The 7510/3510 chip used in cheapo POS power supplies has overvoltage/undervoltage protection BUT NO overcurrent protection. It was my intent to show that most Bestec power supplies have overcurrent protection using the circuitry I have been describing.
I spent much time working a problem on a Bestec ATX-400...Leave a comment:
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Re: 7310/3510 supervisor chip with overcurrent protection
The drawing in the first post is from a Bestec ATX-250 12Z which does use a LM358 chip. Notice that there is a diode between the op-amp output and pin 6 of the supervisor chip. Therefore the LM358 does not need to be open collector output. The Bestec ATX-400 uses a LM339 which is open collector and therefore does not need the diode between the op-amp output and pin 6 of the supervisor chip....Leave a comment:
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Re: 7310/3510 supervisor chip with overcurrent protection
The explanation of this circuit is as simple as I could make it. The figures have also been simplified for explanation. This circuitry is used in the Bestec ATX-250 12E, ATX-250 12Z, ATX-300 12E, ATX-300 12Z, ATX-400, and several other Bestec models. I don't know if any other brands and models are using this type of overcurrent circuitry. This forum is for power supply design and engineering. So it is possible to take a cheapo POS without overcurrent protection and add an outboard overcurrent circuit on a small piece of perf...Leave a comment:
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Re: 7310/3510 supervisor chip with overcurrent protection
Referring to Figure 4, the output of one of the comparators is added to the circuit. When circuit operation is normal, the output of the comparator chip is high (open collector output) and 5.3 volts is at pin 6 of the 7310/3510 chip. When an overcurrent condition is detected the comparator chip switches and goes low taking pin 6 of the 7310/3510 chip to ground causing the supervisor chip to shut off the power supply. Both overcurrent comparator outputs are connected to pin 6 of the supervisor chip, either directly or through...Leave a comment:
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Re: 7310/3510 supervisor chip with overcurrent protection
Referring to Figure 2, a simple voltage divider consisting of R1, R2, and R3 is between the +12 volt line and ground. The voltage across R3 sets the voltage going to pin 6 of the 7510/3510 chip at 5.3 volts. This is well within spec for what the 7510/3510 chip expects as normal. In Figure 3 diode D1 is added between the +5 volt line and the junction of R1 and R2. The voltage at this junction is normally 5.6 volts. If the voltage on the +5 volt line goes below 5 volts, diode D1 begins conducting. The reduced voltage on the...Leave a comment:
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Re: 7310/3510 supervisor chip with overcurrent protection
Referring to Figure 1, a comparator chip has inputs attached to the input and output of the PI output coil. The voltage across the PI output coil determines whether the output of the comparator chip goes hi or low. For normal operation, the output is high. When overcurrent is detected the output goes low. The Bestec ATX-250 12Z uses a LM358 chip which has two op-amp comparators, one used for the +5 volt line and one used for the +12 volt line. The value of resistor R1 in Figure 1 sets the overcurrent limit amount. I don't...Leave a comment:
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7310/3510 supervisor chip with overcurrent protection
In the past I have read comments from those who criticize power supplies as being cheap POS because of the 7510/3510 supervisor chip which has no overcurrent protection. The purpose of this thread is to challenge this generalized complaint to prove it just is not true. Half bridge power supplies I have worked on do not use the 7510/3510 supervisor chip. It is often used in the current forward class of power supplies. That being said (and can be disputed), I am using a very commonly found Bestec ATX-250 12Z as a reference for the circuit description which follows. Below is a drawing of the overcurrent...Last edited by everell; 12-14-2020, 09:27 AM.
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