PCB from wine fridge

[trex66]

I have a PCB from a Haier wine fridge (HVT18DFBB) that powers two thermoelectric units. when I got the fridge it had two TEC1-12706's (12V, 6A) that were not working. I replaced them with two 12709's (12V, 9A)The problem now seems to be that the units are under powered and it takes over a day to get to the correct temperature.

I can't find any information on the web on this board, it's labeled GCH-A35(20070105) Part# is RF-5210-37. The PCB is a 1.9A 130Watt. The current going to the TEC's is 3A at 12V. The PCB seems to be working correctly, but I would expect to see something closer to 6A at 12V going to the TEC's. The D83 004 Schottky is rated for 30A, when the fridge is on this Schottky and heat sink get very hot.

Anyway, I wanted to know it it was possible to increase the current going to the TEC's? I would like to give each TEC 6-9A

[Dgtech]

Re: PCB from wine fridge

when I got the fridge it had two TEC1-12706's (12V, 6A) that were not working. I replaced them with two 12709's (12V, 9A)The problem now seems to be that the units are under powered and it takes over a day to get to the correct temperature.

Something is telling me that it's not the current output that is failing you but the load on the circuit may not be correct. What was the output from the original power supplies? Were their Schottky's getting too hot?

If the load in this circuit is the compressor, maybe it's not correct somehow. Although, I've seen that the load usually increases and draws more current from a faulty compressor but I could be wrong.

[Krankshaft]

Re: PCB from wine fridge

The cooler doesn't use a compressor it uses two Peltier cooling modules. This is a less efficient way for cooling it's mostly used on small portable 12 volt powered fridges. One side of the module gets hot and usually has a heatsink on it and the other side gets cold.

If you want a good cooler with quick thermal recovery get a compressor driven unit. They're simpler and last practically forever.

So you replaced the stock cooling modules with new ones that draw a higher current? Of course the secondary rectifiers are overheating the current being drawn from the PSU is too high.

You need to find cooling modules with a max draw of 6 amps not 9. Surprised the power supply didn't die.

These cheap Chinese Haiers have the power supply rated for not a milliamp more than needed. It can't absorb that monumental increase in current draw from the new modules.

[trex66]

Re: PCB from wine fridge

[QUOTE=So you replaced the stock cooling modules with those that draw a higher current? Of course the secondary rectifiers are overheating the current being drawn from the PSU is too high.

You need cooling modules at a max draw of 6 amps not 9.

These cheap Chinese Haiers have the power supply rated not a milliamp more than needed.[/QUOTE]


Is it possible to replace the schottky with one that will supply a higher current or will I have to change every component to get my 9A TEC's to work? Maybe I should just get 6A TEC's and forget about it.

[Krankshaft]

Re: PCB from wine fridge

You would have to redesign the whole power supply and change the input rectifiers, switching FET, switching transformer, and output rectifier. All of these devices are rated for a certain max current that can safely flow through them without the risk of a burn out.

A switcher is a tightly knit system you can't just swap out one component.

[trex66]

Re: PCB from wine fridge

Thanks, that's the info I was looking for - one last question, shouldn't the TEC's be getting close to 6A at 12V I'm only reading 3A. Is there something that could be causing it to only give 3A?

[steve2]

Re: PCB from wine fridge

Is the top and bottom of the cooler working. There is a cooler for top and another for bottom.

[trex66]

Re: PCB from wine fridge

Yes there are two areas in the fridge separated by a solid shelf. There are two TEC units run off one power supply. The top area should get down to 45˚F and the bottom to 54˚F. they will both get to 55˚F in about an hour or so. The top unit will stay on and try to get to 45˚F. It will get to 48˚F but it takes three days. The fridge is inside a room that is 70˚F. In theory, the temperature differential should be over 170˚F @ 6A, 12V. It just doesn't seem like the units are getting 6A even 3A should be enough to get a bigger temperature swing.

[trex66]

Re: PCB from wine fridge

what controls the current, is there something I could check to make sure it is working correctly?

[Krankshaft]

Re: PCB from wine fridge

There is nothing controlling current. Current is drawn from the power supply the supply is being overloaded the new modules are trying to draw 18 amps out of the supply which is causing a drop. From the factory it was only designed to supply 12 amps to two 6 amp modules.

[trex66]

Re: PCB from wine fridge

Thanks for all the help, everyone. I'm going to get some 6A modules and I'll post back.

[david heise]

Re: PCB from wine fridge

Not a supply question but here goes: I have replaced the TEC1-12706's in several of these wine coolers due to failure. All were "sealed" with white RTV silicone sealent around the edges. I'm a curious sort and have disassembled them all to find that in EVERY case, there has been a green colored corrosive inside which, I'm sure, led to the premature failure. Also, the sparse amount of heat sink compound used (on both plates) is appalling - it invariably dries up and adds to the problem. If moisture is going to permeate the module regardless of the silicone seal, why bother? Seems to me if air were allowed to circulate freely around the semiconducting elements, corrosion may not be as much of a problem.
Any comments?

[david heise]

Re: PCB from wine fridge

Here's a photo of the corrosion that I referenced........