Dodgy PCB

Busta_Gonad

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I have a dodgy PCB, out of my thermoelectric Wine Cooler, I know its dodgy, the things are like rocking horse poop though, how do i go about fault finding on it, any of you real techies be of any help?
 
Peltier drive thing?

High resolution picture of both sides please :).
 
What are the symptoms of the fault? And have you done any tests at all?
 
the wine cooler has 2 power boards (exactly the same) one for top compartment (running 2 fans and 2 peltiers) and one for the bottom cpompartment (1 fan & one peltier) this board is runnin the bottom compartment and lights and temp gauge, with the back off, the fan is trying to turn, but failing, you can hear a clicking from the board, and the light is flicking in time with the clicking.

If i swap out the fan into the other power board, it works fine, take power from the board, the lights go out, the fan stops (and i assume the pelteier too)
 
ive fixed a few Thomson sky / freeview boxes with the same fault description. all ive done to rectify the fault was to replace the electrolytic capacitors.. (beer can looking things). check them for swelling or leakage. if in doubt swap them out.. you can use higher voltage ratings but NEVER lower and keep the same uF values.. of course this is only what ive done with other power supplies and may not be the cure for yours.. just remember these power supplies still have stored energy (when disconnected) in the large capacitors, its a good idea 2 short them out with a resistor before de-soldering... hope this helps
 
the wine cooler has 2 power boards (exactly the same) one for top compartment (running 2 fans and 2 peltiers) and one for the bottom cpompartment (1 fan & one peltier) this board is runnin the bottom compartment and lights and temp gauge, with the back off, the fan is trying to turn, but failing, you can hear a clicking from the board, and the light is flicking in time with the clicking.

If i swap out the fan into the other power board, it works fine, take power from the board, the lights go out, the fan stops (and i assume the pelteier too)

It looks to me like there are 2 switch-mode power supplies on the board. If I am correct, they run in parallel. The smaller of the 2 is a low-power standby supply to power the thermostat, display etc. The larger supply is supposed to kick in to power the peltier(s), but if faulty it will just continually trip & re-try- hence the clicking/LED flashing you are experiencing. Numerous things can cause PSU failure- cap's as @jondoe says, (though yours look ok) there are also pairs of high value resistors in the start-up circuit (R41 & its twin or the other pair- can't make out their ref's) that can go open circuit, it could also be something in the feedback circuit- harder to trace but less likely.
 
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the wine cooler has 2 power boards (exactly the same) one for top compartment (running 2 fans and 2 peltiers) and one for the bottom cpompartment (1 fan & one peltier) this board is runnin the bottom compartment and lights and temp gauge, with the back off, the fan is trying to turn, but failing, you can hear a clicking from the board, and the light is flicking in time with the clicking.

If i swap out the fan into the other power board, it works fine, take power from the board, the lights go out, the fan stops (and i assume the pelteier too)

If I am reading this correctly, you have 2 identical PSU boards. One is working, the other isn't. So, you have one known good set of components on one of the boards available for comparative basic component resistance checks including diode/semiconductor junction networks. This may give you a clue to where the problem is, but it also means that you have a source of identical parts for test substitution, if you are handy with a soldering iron.

As already mentioned, the most likely suspect is capacitors, particularly the two on the top right. They look alright but it's difficult to tell from the photo.
I only know two ways to check capacitors in switch mode PSUs. One way is substitution (from the known good PSU, or a new replacement).
Unfortunately, that will be time consuming with the number of caps on the PCB, unless you get lucky.

The other way is to use an equivalent series resistance (ESR) tester, or a multimeter with that function. Ordinary capacitance "value" testers aren't much use.
An ESR tester can be used in situ (usually without the need for removal) and will reveal suspect caps immediately.
Also check the PCB soldering for dry joints, particularly on any components that get hot.

TBH my experience with switch mode supplies in general, is to swap the caps. If that doesn't work, and there is no obvious evidence of other component failure, scrap it.
Like many things these days, repair is not likely to be cost effective, even if you can identify and source replacement components.

If you don't get anywhere, and can't get another PSU at a reasonable price, I have an ESR tester and can easily check/replace the PSU caps if you post it to me.
 
Have a word with your local tv engineer. He will have the equipment and the knowledge to find the fault and repair it.
In this current economic climate many of us are turning our hands to all types of equipment repair
 
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