Here is a Starpower Model PIV550 (peak load 450 watts), probably better known as a POS not really worth messing with. However, I accepted the challenge. The 5VSB was working, but the power supply was otherwise dead. I began by using a scope to look at the output signals on the 7500 PWM chip. No signals. Next I looked at the Vcc on the 7500 pwm chip which was a pulsing signal rather than DC voltage. I determined that the filter capacitor on the 5VSB feedback line was totally open. Replaced this 470 uF capacitor and the power supply came back to life, but no power good signal. So I decided to do a capacitor study on this power supply.
All of the output capacitors were Sus'con, and all of the small capacitors were Fuhjyyu. Strange combination! One of the output capacitors on the 3.3 volt rail was Sus'con 2200 uF/10 volts but measured 1480 uF with esr 0.09. Replaced it with a Jamicon pullout measuring 2350 uF esr 0.02. All other Sus'con capacitors on the outputs measured OK for capacitance and esr.
ALL of the small Fuhjyyu capacitors were a different story. I used measured pullouts for replacements. What I found was as follows:
1.0 uF/50 volts measured 2.16 uF esr 5.2 replaced with Jamicon measured 1.09 esr 2.9
1.0 uF/50 volts measured 1.33 uF esr 8.0 replaced with Jamicon measured 1.06 esr 2.9
10 uF/50 volts measured 11.4 uF esr 1.9 replaced with Teapo measured 10.53 esr 0.75
2.2 uF/50 volts measured 2.25 uF esr 32 replaced with Jamicon measured 2.31 esr 1.9
4.7 uF/50 volts measured 3.94 uF esr 13 replaced with Nichicon measured 4.65 esr 0.53
4.7 uF/50 volts measured 4.41 uF esr 10 replaced with Nichicon measured 4.43 esr 0.55
4.7 uF/50 volts measured 3.70 uF esr 18 replaced with Nichicon measured 4.58 esr 0.59
5vsb output capacitors Sus'con:
470 uF/10 volts measured 316 uF esr >99 replaced with Sus'con 1000 uF measured 930 esr .06
470 uF/10 volts measured 364 uF esr .42 replaced with Sus'con 1000 uF measured 930 esr .06
-12 volt output capacitor Sus'con
470 uF/16 volts measured 282 uF esr 28 replaced with Chemicon measured 474 esr 0.01
-5 volt output capacitor Sus'con
470 uF/10 volts measured 340 uF esr >99 replacement not logged
Swithcing transistor base driver capacitors Fuhjyyu
1.0 uF/50 volts measured 1.62 uF esr 11 replaced with new Nichicon 4.7 uF
1.0 uF/50 volts measured 2.05 uF esr 7.3 replaced with new Nichicon 4.7 uF
As can be seen, many of the Sus'con capacitors were in good shape, but ALL of the small Fuhjyyu capacitors were very bad. This demonstrates that replacing the bad bulging large capacitors but assuming that the small non bulging capacitors are good is a bad idea.
I also added line filter coil and capacitor. Now I don't have to call it a cheap POS.
All of the output capacitors were Sus'con, and all of the small capacitors were Fuhjyyu. Strange combination! One of the output capacitors on the 3.3 volt rail was Sus'con 2200 uF/10 volts but measured 1480 uF with esr 0.09. Replaced it with a Jamicon pullout measuring 2350 uF esr 0.02. All other Sus'con capacitors on the outputs measured OK for capacitance and esr.
ALL of the small Fuhjyyu capacitors were a different story. I used measured pullouts for replacements. What I found was as follows:
1.0 uF/50 volts measured 2.16 uF esr 5.2 replaced with Jamicon measured 1.09 esr 2.9
1.0 uF/50 volts measured 1.33 uF esr 8.0 replaced with Jamicon measured 1.06 esr 2.9
10 uF/50 volts measured 11.4 uF esr 1.9 replaced with Teapo measured 10.53 esr 0.75
2.2 uF/50 volts measured 2.25 uF esr 32 replaced with Jamicon measured 2.31 esr 1.9
4.7 uF/50 volts measured 3.94 uF esr 13 replaced with Nichicon measured 4.65 esr 0.53
4.7 uF/50 volts measured 4.41 uF esr 10 replaced with Nichicon measured 4.43 esr 0.55
4.7 uF/50 volts measured 3.70 uF esr 18 replaced with Nichicon measured 4.58 esr 0.59
5vsb output capacitors Sus'con:
470 uF/10 volts measured 316 uF esr >99 replaced with Sus'con 1000 uF measured 930 esr .06
470 uF/10 volts measured 364 uF esr .42 replaced with Sus'con 1000 uF measured 930 esr .06
-12 volt output capacitor Sus'con
470 uF/16 volts measured 282 uF esr 28 replaced with Chemicon measured 474 esr 0.01
-5 volt output capacitor Sus'con
470 uF/10 volts measured 340 uF esr >99 replacement not logged
Swithcing transistor base driver capacitors Fuhjyyu
1.0 uF/50 volts measured 1.62 uF esr 11 replaced with new Nichicon 4.7 uF
1.0 uF/50 volts measured 2.05 uF esr 7.3 replaced with new Nichicon 4.7 uF
As can be seen, many of the Sus'con capacitors were in good shape, but ALL of the small Fuhjyyu capacitors were very bad. This demonstrates that replacing the bad bulging large capacitors but assuming that the small non bulging capacitors are good is a bad idea.
I also added line filter coil and capacitor. Now I don't have to call it a cheap POS.
Attached Files
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