/diy/ - Do It Yourself

>>2034505

>>2034559
I looked up the black square plastic thing, but dunno if that’s the problem or not. I can like do basic soldering.

>>2034505
Yellow stuff is flux or some sealant, don't worry about the caps on the board.
If the compressor isn't getting any power, your relay (big black box in the middle) may be bad.
Could also be the transistor that drives the relay.

>>2035423
Here’s a pic of what that black thing has written on it. So it’s a relay? As in power in/power out, but only when a signal is given from the temperature sensor? I looked up the JQX# and it’s pretty cheap on Amazon and it looks like a simple 4 pin soldering job I can handle.
>Could also be the transistor that drives the relay.
Which one is the transistor?

Thanks for the reply!

>>2035447
The transistor controlling the relay coil is either BG1 or BG4. those in turn are controlled by the microcontroller

>>2035447
>So it’s a relay?
Yep. Its kinda like a switch that uses an electromagnet to turn the switch on and off. Four pins, two go to the electromagnet and two are the pins to the switch. It uses low voltage (about 12v) to close the internal switch, which allows the 120v wall power to go to the compressor. Moving parts and high power causes failure at some point.
>Which one is the transistor?
BG4, the black, 3-pin part.
From what I can see, its an NPN transistor. The Emitter is going to ground, the Collector is connected to the relay. Resistor R9 beside it connects the Base to the Atmel ATMEGA microcontroller which is the brain.
Transistors are kinda like a switch, they use low current to allow a bigger current to pass. They can go bad too, so if it went bad, the relay won't get power to its electromagnet to turn on.

>>2035700
>BG4
Scratch that, its BG1 that drives the relay, with R6 connecting it to the microcontroller. My brain is being dumb.

>>2035700
Is it possible to apply the 12v to the bottom two pins with a car battery and see if that makes continuity between the L1 and L0.

>>2035704
BG4 controls the buzzer through R9 and the microcontroller

>>2035931
>with a car battery

no car batteries, ever! they have a lot of energy and will easy blow components apart if you touch it to the wrong place.

you can use the board's own 12V power to do it. just connect the leg of the diode marked in black to a ground point. the leg marked in red should be already connected to +12V so that'll put 12V across the relay which will make a clicking sound if the electromagnet is working. when it clicks, that should short L0 and L1, but not necessarily, coz the relay's switch contacts could be damaged.

so where can you find a ground point? a quick look tells me it's the trace where i drew ground symbols on, which travels all over the PCB, but i'm not 100% sure, so maybe someone else can confirm.

>>2036063
>BG4 controls the buzzer through R9 and the microcontroller
Yep, I swapped locations in my head when I was switching between photos, hence why I corrected myself.

>>2035931
>Is it possible to apply the 12v to the bottom two pins with a car battery and see if that makes continuity between the L1 and L0.
Yes, you can, make sure you have a steady hand and only touch the right spots.
On pic related, I circled the relay coil points that you can use a 12v battery on, with polarity. Normally, the relay doesn't care about polarity, but this is in respect to other components on the board. Touch Batt+ to the red circled point and batt- to the black circled point. You should hear a click when you apply voltage.
To properly test it though, hook up the battery to the relay and use your multimeter on the green and red spots that you originally circled, labeled LO and LI. Do a continuity check, or resistance depending on what your multimeter can do. The reading should be "closed," "short," zero resistance, something like that. It should be a complete connection. If you get something like "open" or infinite resistance, the relay is busted.
Optionally, you can connect the main power connector that goes to the wall and connect a small piece of wire between the two points I marked in orange. That is the transistor that drives the relay, and connecting those two points will bypass the transistor. Be careful if you do this method, high voltage will be active on the board, and you do NOT want to accidentally connect any points except those two marked in orange specifically.

>>2036226
Part 1 is testing the relay, So if the 12v applied to your red/black marks works and properly makes the relay click and gives continuity between L0 and L1, then it’s a good relay. If not then I know that’s the problem and should replace the relay.

Part 2 is testing the transistor if the relay test is good. Jumper the orange points to bypass the transistor and plug in. Now what behavior will I look for? Since the transistor is by passed will the compressor be always on? Or will it still be awaiting the signals from the microprocessor?

I’ve got some low voltage wire and about to do some soldering

>>2036246
>>2036226
Ok I put some small batteries together and got 12v. I put a continuity test across the incoming/outgoing pins L0/L1. When I apply 12v across the points you mentioned, the relay clicks and depending on how well the connection I make is I hear a rapid beep (from bg4?)
>>2036063
The buzzer beeps when I apply 12v across the points in addition to the relay clicking

So this means the relay is good right?

>>2036327
>So this means the relay is good right?

yes, and that's a bad thing. coz when you trace that back you have only the transistor or computer as the problem, and replacing the computer is probably impossible. of course, the computer could be just fine, and the reason it doesnt turn on the relay is that some sensor is bad, or a connector is loose, or a million other misc things.

>>2036327
>So this means the relay is good right?

yes, and that's a bad thing. coz when you trace that back you have only the transistor or computer as the problem, and replacing the computer is probably impossible. of course, the computer could be just fine, and the reason it doesnt turn on the relay is that some sensor is bad, or a connector is loose, or a million other misc things. back to square 1.

>>2036346
have we ruled out the transistor yet? the orange points BG1 >>2036226 are emitter and collector. we've only bypassed BG1, not activated it. need to bodge in like a 4.7k resistor from collector to base to actually test it

>>2034566
>>2036246
Reflow every connection on the board.

>>2036346
I know testing components while still on the board is inconclusive. But I just did a quick continuity test on the two transistors BG1/BG4 that you and the other guy were talking about.

I couldn’t get any continuity reading on BG4, no matter what combination I used, it seems like a good transistor should beep somewhere right? On BG1 I was able to get reading by putting negative lead on collector and the positive on the Base/emitter, both gave continuity and no other combinations worked.

So was BG4 the important one, if it didn’t work would it cause the symptoms? I could try and remove it and test for real if you think I should, but does lack of reading def mean it needs replacement? Also should I do more tests on BG1? Does the buzzer going off when I applied 12v have any significance?

Thanks everybody

>>2036386
If I’ve exhausted all the trouble shooting,I could like put it in the oven I guess. I think I’ve got a hot air station also

>>2036396
>it seems like a good transistor should beep somewhere right?

if it beeps it's shorted (ie. dead)
you'd need a multimeter with a diode function to test them.

>>2036407
Don't put it in the oven. Apply flux to the solder joints and reflow them with an iron.

>>2036409
I’ll check if my multimeter has that or not, I just did a continuity across the cbe in different combos to figure out if pnp/npn
BG1 had no continuity in any combo
BG4 had continuity in the way I described before

I guess I don’t know enough to say whether the reading is good or bad

>>2036412
What kind of flux do I need? I’m always just heating a component up to pull out and using the solder that stayed put when putting it back

>>2036423
Anything is better than nothing, but rosin paste flux is fine. Clean it off with isopropyl alcohol and a brush when you're finished.
You'd be surprised to know how often a cold solder joint (or several) makes everything not work.