Seeking Datasheet for 53A3P IC -- Switching IC Used in Appliances

[Callixus]

That image was not very helpful since it doesn't say what 1, 2 and 3 are . . .

[Callixus]

Not a very helpful image, above, since it doesn't say what pins 1, 2 and 3 are . . . See attached.

[R_J]

That image was not very helpful since it doesn't say what 1, 2 and 3 are . . .

I used the same size font as the rest of the components; I will enlarge that portion of the board for you to see the numbers.
Your picture does not show the numbers on Q2, but configured as it is to drive the relay, the base would need to be driven by U2
If it was reversed, the base would be connected to ground.
If the transistor lead was broken, that would explain why it was not working.

[Callixus]

Ah . . . OK! . . . I was just so focused on the numbers on the 53A3P IC . . .

Well, we'll see about the transistor. IF that one is the one I did not pull, and if it was already broken (after all, I was amazed this morning when I thought I had broken it just tilting it a little, because it was literally going to be the most brittle thing ever seen . . .)

I should have one on Tuesday.

Thanks again!

[Callixus]

Well, with high expectations, I soldered in the new C945 transistors. With great anticipation did I plug it in. With bated breath, I pressed the switch.

Nothing.

OK, so really back to the drawing board. If you have any patience left for your student, here is what I'm doing, and feel free to steer me down other avenues. I know this is all sort of ridiculous for an ancient coffeemaker, but I am learning a lot and if I make a mess of it, well, it's just an ancient coffeemaker:

1. I am just going through the entire board. First, I have just examined everything for dry/loose solder joints, bits of whatever bridging things that should not be bridged, etc. Now I am undertaking just going through it all, component by component, but with a bias towards testing first those components that are not related to the 24V side of things. This is because, with your help, we have already established that we are getting 26V across EC1.

2. So, I am excluding the "AC/Full Bridge Rectifier Section" from my efforts. See partially obscured portion of board in image below. Do you agree? Have I been over- or under-inclusive in what I am excluding? I am just thinking that the IC is not getting the proper signals because of faults with other sections/components.

3. We exchanged messages about how R3 is connected to the AC power, and then connected to R8, and then R8, via JMP1, connects to this area communicating with both the IC's Pin 2 and also, through diodes, etc., Q1. R3 seems to be a 100Ω resistor; R8 seems to be a 1.8MΩ resistor. De-soldering one lead off of each resistor, this is what they measure. Yet when I measure the entire chain from the where the AC power is attached, through R3, etc., to the somewhat triangular area that is tied to IC Pin 2, etc., I get 635KΩ. I'm not getting too excited yet because I realize there are things going on in parallel, but I thought I'd mention it.

4. Note that I have exculpated the AC coil switching side of the relay: There is no detectable leakage across the open switch part of the relay. And weeks ago I was able to activate the coil portion with batteries and a resistor, so my guess is that the relay is something I can also ignore.

So, what do you think about me excluding the AC/Full Bridge Rectifier Section? Do you otherwise think I am going about this the right way?

I really wish I had a schematic for that IC . . . I was doing some reading about optoisolators, and the one I came across uses all eight pins: On the one side, four pins total are used essentially as a pair of unconnected, internal LEDs, all to activate two independent photosensitive switches on the other side, so to have two potential circuits. But as we have seen, one pin (Pin 3) on what I am looking at is not connected at all, etc., and the table you sent me has stuff I don't follow very well. For example, there's this: "±5V to ±18V (Dual Supply) or 10V to 36V (Single Supply)". That's in the "Supply Voltage" row of the table. I am not convinced that the IC itself needs a voltage supply, since it's not a microcontroller, etc. So are we talking, here, about the IC serving as either a single or dual supply? Does the fact that Pin 3 is "NC" mean that in our case the chip is used as a single supply?

Sorry for all of the questions, but even this last thing has me thinking and trying to understand. After all, the coil would seem to be at least double-isolated (relay + transistor) and if somehow the IC is intended (apart from just more switching) to isolate from the coil, that would be triple isolation.

Anyway, whatever guidance and input you can give would be appreciated. Thanks!

rbp

[mateusassuncao]

Hi, how are you?

It seems you have a dual-channel optocoupler (53A3P) on your board.
Its purpose is to galvanically isolate two circuits, commonly used in high-voltage circuits for feedback to low-voltage circuits, or sometimes to separate AC and DC circuits.

From what I understand on your board, Q2 controls the relay, and according to the images shared by our friend R_J, the base of Q2 is driven through a resistor by pin 6 of U2.

Is there any voltage present on this pin when the device is powered on?
If so, we could rule out a fault in U2 for this output channel.

[Callixus]

I am fine, Mateus. Welcome to my silly educational exercise!

R_J has been extremely helpful.

Remember: The switch is a momentary contact switch. Since I don't have an analog meter, my results may not be completely indicative of the situation.

It seems there is ZERO voltage at Pin 6 whether when pressed momentarily, pressed and held, or not pressed at all. (Well, actually about 60 millivolts seem to be present . . . But that's true elsewhere as well . . .)

BUT GET THIS: I tried shorting Pin 5 to Pin 6. This triggered the relay and, in addition, the heating / boiler coil started heating! AND the LED indicator (part of the switch and not on the board you've seen) lit up! All of this lasted only so long as I kept Pins 5 & 6 connected. So that's useful information I think: That is SUPPOSED to be the switch both for the heating and the LED, and I think those are the only things that get switched at the lowest level (i.e., excluding layers of isolation and just talking about what needs to be switched to make the coffeemaker act like a coffeemaker -- the "I want it to heat and boil the water and I want to see an LED whenever it's heating" level . . .).

The voltage at Pin 5 is a touch over 3.5V when not bridged, and then when Pins 5 & 6 are bridged, they are at about 2.8V.

Without touching the button, Pin 1 is getting about 4.9V; Pin 2 -- 2.63V; Pin 3 -- 160mV; and Pin 4 again about 4.9V. On the other side you can see what is going on with Pins 5 & 6. Pin 8 shows as a ground, and Pin 7 also shows 0V -- and that, to me, seems suspicious. After all, I think Pin 7 is suppose to be connected to the MC switch to start the whole rodeo, but its value is precisely what the value is on the other side of the switch -- GND.

Some other information from above in this thread that you may not have seen: I replaced Q1, Q2, and U2. I have reasonable faith in the quality of the new transistors. U2 almost looks too new to be the real deal, with big white characters. It might be a block of plastic with metal legs implanted for all I know.

WHAT I HAVE NOW DONE: I tested for continuity between the pins on the header for the switch, to see if Pin 7 is shorted to ground on the board somehow. It's not. I then tested for continuity and function between the yellow and brown (GND) wires of the switch harness, to look for any shorting in the off-the-board portion affecting Pin 7. It's not shorted there and the switch works. Also, if held down (against its internal spring, in other words), it stays closed -- which might be useful for testing at some point.

Thoughts?

Thanks to you and to R_J!

[mateusassuncao]

Look, let’s see if the problem is really with this control and status board (relay)! Well, what happens is that the signal comes from a microcontroller or a timer! Have you already tested if the execution board is receiving the signal from the control board? No project is silly — electronics in boards worth thousands of dollars or just one dollar… it’s all electronics, my friend! I respect them, from manufacturing onward! I love electronics, any kind it may be....
and...
Describe the wiring harness! Or is there a main board that sends commands to this one? Would that be it?