help with wine cooler-something buzzing

[buchman]

Re: help with wine cooler-something buzzing

Maybe there is nothing wrong with the psu and just something else drawing too much current from it? So if you plug in the psu into mains by itself with nothing connected, that transistor that got hot should stay cool.

Even if I disconnect everything, the transistor is getting hot.

[buchman]

Re: help with wine cooler-something buzzing

my suspect would be the choke coil next to the heatsink.

Can someone show/explain where's it exactly?

[buchman]

Re: help with wine cooler-something buzzing

Take out the transformers and coils, dip them in lacquer/varnish for a few hours, take them out and allow to dry for 24 hours, solder them back in. Your buzzing problem should be solved.

What is lacquer/varnish? maybe in my country it called something else. I don't want to ruin completely the components.

[CapLeaker]

Re: help with wine cooler-something buzzing

Interesting. So even with no load on the PSU the transistor is still getting hot. That shouldn't be. I would probe around, see if the output is stable, the voltages around the IC is good etc. The LED is driven from the other side though... maybe replace CA1 and the big cap above it? Check D6 and R28? Take that big inductor out and solder it in again, maybe there is a bad solder joint. After that I'd be replacing the ICs.

varnish = like a clear coat for wood found on furniture, window frames, boats etc.

[buchman]

Re: help with wine cooler-something buzzing

Interesting. So even with no load on the PSU the transistor is still getting hot. That shouldn't be. I would probe around, see if the output is stable, the voltages around the IC is good etc. The LED is driven from the other side though... maybe replace CA1 and the big cap above it? Check D6 and R28? Take that big inductor out and solder it in again, maybe there is a bad solder joint. After that I'd be replacing the ICs.

varnish = like a clear coat for wood found on furniture, window frames, boats etc.

checked every thing already. every diode on the pcb and every resistor around the transistors.

when you say INDUCTOR, you mean the golden ring near the brown capacitor?

[CapLeaker]

Re: help with wine cooler-something buzzing

Yeah, that golden ring with the wire wound around it.

I remember one instance on a different PSU that a certain resistor was good while it was out of circuit. However once there was a load on it, it went high in resistance, thus making the PSU shut down. Another instance, where a inductor wasn't properly soldered and made the output voltage go all over the place.

If this yields nothing, replace that big IC, since it is getting fed from the little transformer. Check /replace the two little transistors T4 and 5. Check C18 and 19. Plus that long big red capacitor.

As per your pictures it looks to me that the display is actually driven by the big transformer. So you have 2 issues?

I think there is only one thing that gets powered from the little transformer and that goes to the plug LED?

[buchman]

Re: help with wine cooler-something buzzing

Yeah, that golden ring with the wire wound around it.

I remember one instance on a different PSU that a certain resistor was good while it was out of circuit. However once there was a load on it, it went high in resistance, thus making the PSU shut down. Another instance, where a inductor wasn't properly soldered and made the output voltage go all over the place.

In this case, I need to replace each and every resistor?!?!

[buchman]

Re: help with wine cooler-something buzzing

As per your pictures it looks to me that the display is actually driven by the big transformer. So you have 2 issues?

Define 2 issues?
When I plug the wine chiller, the display blinks and beeps as if you are pressing one of the buttons.


[/QUOTE] I think there is only one thing that gets powered from the little transformer and that goes to the plug LED?[/QUOTE]

I don't know. How can you tell? I am always confusing where the traces go because they split.
If you can explain in two words how to know which trace goes where... I would appreciate that.

[CapLeaker]

Re: help with wine cooler-something buzzing

In this case, I need to replace each and every resistor?!?!

Nope, in my case it was the resistor that fed the PWM IC. I watched the voltage disappear. Was a dead give away on the voltage measured on each leg of the resistor.

[CapLeaker]

Re: help with wine cooler-something buzzing

Define 2 issues?
When I plug the wine chiller, the display blinks and beeps as if you are pressing one of the buttons.

I think there is only one thing that gets powered from the little transformer and that goes to the plug LED?[/QUOTE]

I don't know. How can you tell? I am always confusing where the traces go because they split.
If you can explain in two words how to know which trace goes where... I would appreciate that.[/QUOTE]

feed the display with a different PSU, something that has CC / CV.

Sorry, made a mistake... not the LED plug, i meant the NTC plug.
The AZ494 IC has a DUAL output, maybe one bad?

[buchman]

Re: help with wine cooler-something buzzing

What is CC/CV?

Can I test the ic with a DMM or I need some special equipment?

[CapLeaker]

Re: help with wine cooler-something buzzing

it's just a power supply that has constant voltage and constant current. With this you could set the voltage and the current needed without damaging stuff.

[buchman]

Re: help with wine cooler-something buzzing

it's just a power supply that has constant voltage and constant current. With this you could set the voltage and the current needed without damaging stuff.

OK I do have one.

[buchman]

Re: help with wine cooler-something buzzing

Can I test the ic with a DMM or I need some special equipment?

What about this one?

[CapLeaker]

Re: help with wine cooler-something buzzing

Download the data sheet for the AZ494 from the internet.
here: https://cdn.badcaps-static.com/pdfs/...0eb36d87fa.pdf
It will tell you what pin of the IC does what. Start probing around and check for example is there proper Vcc, check the reference voltage, etc.

First I would power that display with that other PSU and see how much current it takes for it to run correctly. Also I would make sure to test all capacitors of the wine cooler PSU out of circuit, as they can (depending on the circuit) measure good while in circuit, but actually are bad out of circuit.

[Th3_uN1Qu3]

Re: help with wine cooler-something buzzing

If just one transistor gets hot, replace all components in its base drive circuit. There should be a couple resistors, one capacitor and one or two diodes. Easier to just swap them all instead of taking the time to diagnose, as they are all "jellybean" (extremely common and cheap) parts.

[glentz]

Re: help with wine cooler-something buzzing

In case you are still doing repairs on these types of PSU's. If the big transformer is buzzing, it could be the transistor attached to the black heatsink is bad. That's probably the one that drives the chiller and fans and sometimes it also supplies Vcc to the that 494 IC. If the transistor or IC is bad the PSU may go into "safety" mode which could cause the transformer to buzz. Without any load attached and without control panel, LED and NTC attached I think you should get 12Vdc on the middle pin of that transistor on the black heatsink (actually the heatsink may be connected to the middle pin depending on the type of transistor or if there is an electrical insulator pad between the transistor and the heatsink). For ground, use the black wire marked gnd. This assumes this wire goes to the actual chiller unit. If you don't get voltage then either that chip is bad or something on the high voltage side is bad. The cold vs. hot transistor on high voltage side is a good clue. TH3_un1qu3 response is a good place to start. Also have you checked DC voltage at the AC/DC diode bridge rectifier? That's the 4 diodes nearest the two big capacitors. From 120VAC input to the bridge you should get ~160VDC out. The display flashing would seem to indicate the PSU is producing acceptable voltage. For your fridge, does the flashing mean the NTC (temperature sensor) is not hooked up? If I unplug the NTC plug from my chiller, the display shows an error code.

Good Luck