Replacing power control board in Haier Wine Fridge

[us3rnotfound]

Hi,

I got a wine fridge from Goodwill, a HVT18DFBB. Its thermoelectric coolers did not work, so I bought new ones and hooked them up (there's 2 temperature zones). The temperature in the 2 zones were able to get down to 59F but no cooler.

Then the only item to replace was the circuit board, so I did. I got the RF-5210-37: http://www.repairclinic.com/PartDetail/Main-Control-Board/RF521037/1567065

The problem is, I hook everything up (Fans, thermoelectric modules x 2, and the temperature control) and nothing powers up, no fans spinning, etc.

I have a couple of general questions: Is it possible that the power input from the wall is reversed relative to the other board? If I were to plug it in reverse-polarity, wouldn't those large caps explode? I plug it in and get crickets.

 

[mindless1]

No, being AC without any earth ground connection to the board it won't matter whether it's the AC wall outlet hot, or common, connected the way you have it or reversed. It won't explode the caps because right after the filter circuit is a rectification circuit supplying DC voltage to the caps on the correct half of the AC wave (per diode).

Are you sure you replaced the peltiers (thermoelectric coolers) which some having equivalent specs? If not that would explain their poor cooling capability, since it does seem to be working a little, just not properly. When the old peltiers were in, was it capable of reducing the temperature at all below ambient or not?

What is the voltage the peltiers are spec'd to use? On the pictured PSU header corresponding to the peltier power circuit, you should measure close to this voltage to verify the PSU is working. Of course this means you have the parts out and powered by 110VAC so if you test this, be careful. At least there are bleeder resistors present so when power is disconnected the high voltage capacitors won't keep a charge more than a few seconds. If one PSU doesn't seem to work, repeat the test using the other PSU.

If the right voltage seems to be going to the control board, then it needs examined for proper functionality. Is the PCB for the control board accessible and can you post good top-down and bottom-up pictures of that? One thing I'm interested in is whether it uses a relay to power cycle the peltiers or something more like a SCR /transistor switch arrangement.

With the relay it could be sticking, or with the SCR/transistor you might have either a bad last stage /high-current transistor or a bias transistor immediately before it. Basically you are tracing from the PSU peltier power line along the traces of the control board to see at what point there's an unexpectedly low voltage (with the fridge operating above the set target temperature so it is expected to be in cooling mode at that moment).

My point is that if the PSU is ok then what remains is identifying components on the control board and replacing individual ones if the fault is found, assuming you can solder. If you can come up with any other data like a schematic or block diagram that might also help.