Re: Wine fridge PSU problem
Hi,
I am just getting back to this. Yes, it has been a while, but as they say life happens when you are making other plans.
When last we spoke I was going to order the power switching transistors and replace them and test according to
This being a few years ago what I recall is this:
I cannot remember if the rheostat temperture control was plugged into the board. I know I did not have the fan or the internal thermostat hooked up or peltier initially. I only plugged in the power first to the board first and then plugged the cord in to the outlet. The LED's light up and I thought everything would be fine. I then unplugged the cord and plugged in the peltier unit and then plugged the cord back it rather than putting a resistor across the terminals. Something blew/shorted and the LED's did not come back on and I have put everything aside since then.
The cord has a ground which is screwed to the chassis. The board is screwed into the chassis via some plastic standoffs but as you can see in the picture there is no electrical path connection between the screws and anything on the board. So I imagine it has a floating ground, but am not certain.
I have come back to this thread and read what was posted in the interim.
I have since tested most of the components that I can with my cheap DMM. Now only one of the power switching transistor got ruined in this repair attempt. I am wondering if the reason this one blew is because of the fact that I did not have the other connections made as detailed above and I had the board just sitting there breadboard fashion or if that did not have any effect.
All the resistors seem good and they are within tolerance as far as I can tell. The zener diodes are working. The diodes test good. The transistors are good but what kaboom said makes me wonder if they can test good could they still be bad/leaky and contributing/causing the problem.
The schottky barrier diode tests good. The voltage regulator works. I have hooked the peltier cooler up to a 12V battery and it heats and cools on opposite sides. I can only assume that it works as I am not sure how else to test the peltier.
I do not have and ESR meter so I cannot truly measure any of the capacitors. Though I did relook at them and the one that is south of the inductor before the terminals for the peltier was pointed out to me as looking a little bulged. I took it off it it does seem as though there was some leakage under it. Is it possible for the board by itself to power up as I mentioned and then when the peltier was plugged in since it is across the legs of this capacitor for it to then short out one of the power transitors.
I do not have a ring tester so I cannot check the transformers. Though I ran a test and I place the probes on each side of the transformers it shows as though the meter probes are not connected at all, infinite resistance. I assume, as all three do this and another that I tested from another scrap board, that this is how it is supposed to be and means they are good, correct?
I do not have an oscilloscope so I cannot test the PWM IC. Is it possible that too is bad? Do these go bad and cause a problem that I am describing? I am unable to test the inductor.
Since that attempt did not fix the problem I am assuming there is something else wrong the fried one of the power switching transistor, or is it because everything was not attached?
What would be the most likely cause of the problem, how should I fix it and what should be replaced to get this working again?
Many thanks for your assistance and patience.
Hopefully this time it can be fully repaired.
Hi,
I am just getting back to this. Yes, it has been a while, but as they say life happens when you are making other plans.
When last we spoke I was going to order the power switching transistors and replace them and test according to
This being a few years ago what I recall is this:
I cannot remember if the rheostat temperture control was plugged into the board. I know I did not have the fan or the internal thermostat hooked up or peltier initially. I only plugged in the power first to the board first and then plugged the cord in to the outlet. The LED's light up and I thought everything would be fine. I then unplugged the cord and plugged in the peltier unit and then plugged the cord back it rather than putting a resistor across the terminals. Something blew/shorted and the LED's did not come back on and I have put everything aside since then.
The cord has a ground which is screwed to the chassis. The board is screwed into the chassis via some plastic standoffs but as you can see in the picture there is no electrical path connection between the screws and anything on the board. So I imagine it has a floating ground, but am not certain.
I have come back to this thread and read what was posted in the interim.
I have since tested most of the components that I can with my cheap DMM. Now only one of the power switching transistor got ruined in this repair attempt. I am wondering if the reason this one blew is because of the fact that I did not have the other connections made as detailed above and I had the board just sitting there breadboard fashion or if that did not have any effect.
All the resistors seem good and they are within tolerance as far as I can tell. The zener diodes are working. The diodes test good. The transistors are good but what kaboom said makes me wonder if they can test good could they still be bad/leaky and contributing/causing the problem.
The schottky barrier diode tests good. The voltage regulator works. I have hooked the peltier cooler up to a 12V battery and it heats and cools on opposite sides. I can only assume that it works as I am not sure how else to test the peltier.
I do not have and ESR meter so I cannot truly measure any of the capacitors. Though I did relook at them and the one that is south of the inductor before the terminals for the peltier was pointed out to me as looking a little bulged. I took it off it it does seem as though there was some leakage under it. Is it possible for the board by itself to power up as I mentioned and then when the peltier was plugged in since it is across the legs of this capacitor for it to then short out one of the power transitors.
I do not have a ring tester so I cannot check the transformers. Though I ran a test and I place the probes on each side of the transformers it shows as though the meter probes are not connected at all, infinite resistance. I assume, as all three do this and another that I tested from another scrap board, that this is how it is supposed to be and means they are good, correct?
I do not have an oscilloscope so I cannot test the PWM IC. Is it possible that too is bad? Do these go bad and cause a problem that I am describing? I am unable to test the inductor.
Since that attempt did not fix the problem I am assuming there is something else wrong the fried one of the power switching transistor, or is it because everything was not attached?
What would be the most likely cause of the problem, how should I fix it and what should be replaced to get this working again?
Many thanks for your assistance and patience.
Hopefully this time it can be fully repaired.
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