Hey everyone,
I’ve got an 18 bottle wine fridge that quit. I opened it up to find a SMPS with a blown inrush current limiter which I replaced. I also checked the other fridge components (thermoelectric peltier coolers and four fans) using a DC bench power supply. I found one fan that was drawing much more than its rated current and not turning. I figured this is what blew the power supply.
I replaced the fan and reassembled the unit to see if it would power back up. Nothing. I disconnected the peltier coolers and everything comes to life. Through trial and error I’ve discovered that the power supply will not power up when the peltier coolers are connected. Once I disconnect them the power supply comes to life. Once the power supply is up and running, I can plug the coolers back in and the unit cools perfectly. The coolers seem fine, but the power supply won’t start with the normal load. It shows about 1.9 volts until the heavy load is disconnected. It also has a buzzing/sizzling sound. It’s like it just won’t start with the heavy load on it.
I also noticed that, once up and running, one of the heat sinked power transistors and its associated 250V 330uF input cap is getting very hot. I checked both input capacitors ESR and found them to be at the datasheet max limit. Not obviously bad, but certainly not good. A capacitance check found them to also be at the lower 20% limit. I’ve ordered replacements but haven’t received them yet. Could this be causing the problem? Anything else I should look at?
I’m somewhat new to how a SMPS works. I’d like to use this as an opportunity to learn more about them. Can anyone tell me what type of SMPS this is? I’d like to research it more. Key components consist of two power transistors controlled by a TL494 DIP IC, an isolation transformer, and a Shottky barrier diode.
Photo attached.
Thanks!
I’ve got an 18 bottle wine fridge that quit. I opened it up to find a SMPS with a blown inrush current limiter which I replaced. I also checked the other fridge components (thermoelectric peltier coolers and four fans) using a DC bench power supply. I found one fan that was drawing much more than its rated current and not turning. I figured this is what blew the power supply.
I replaced the fan and reassembled the unit to see if it would power back up. Nothing. I disconnected the peltier coolers and everything comes to life. Through trial and error I’ve discovered that the power supply will not power up when the peltier coolers are connected. Once I disconnect them the power supply comes to life. Once the power supply is up and running, I can plug the coolers back in and the unit cools perfectly. The coolers seem fine, but the power supply won’t start with the normal load. It shows about 1.9 volts until the heavy load is disconnected. It also has a buzzing/sizzling sound. It’s like it just won’t start with the heavy load on it.
I also noticed that, once up and running, one of the heat sinked power transistors and its associated 250V 330uF input cap is getting very hot. I checked both input capacitors ESR and found them to be at the datasheet max limit. Not obviously bad, but certainly not good. A capacitance check found them to also be at the lower 20% limit. I’ve ordered replacements but haven’t received them yet. Could this be causing the problem? Anything else I should look at?
I’m somewhat new to how a SMPS works. I’d like to use this as an opportunity to learn more about them. Can anyone tell me what type of SMPS this is? I’d like to research it more. Key components consist of two power transistors controlled by a TL494 DIP IC, an isolation transformer, and a Shottky barrier diode.
Photo attached.
Thanks!
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