Hi Mateus!

Well, I gave it too much credit perhaps when I called it a "harness": It's just the four wires running off to the momentary contact switch -- Red, Black, Yellow, and Brown. The red and black wires power the LED that's in the momentary contact switch. The yellow and brown are just for the momentary contact impulse. R_J numbered the pins for the socket to which the "harness" attaches 1-4 in certain images, above.

And, there is no other board. This is the ONLY board. It's just an old Cuisinart coffeemaker. I used to think there was a...

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,...

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...

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!...

I am getting 26V across the electrolytic capacitor, once the load resistor is excluded! Thanks for that!

ZD2 had nothing to do with it. I was out to lunch about that.

OK, so back to the drawing board as to the rest, because the unit doesn't work. I guess I just have to go through it really methodically.

It seems we have a nominally 24VDC power supply and then also a 5.6VDC power supply. But I really want to try to understand this: What is going on with this connection of a leg of the 120VAC, essentially, through to the control chip? See your markup and route...

I am still stumped.

My diode kit arrived. Upon a very close inspection, I did discover some very faint markings on ZD1, and they seemed to be 1W4745A. I had to assume that the "W" was a blotchy "N" or that they just used a "W" back when they made this. Anyway, that corresponded to a 16V Zener, so that's what I put in.

It didn't work.

Probing around, my dodgy jumper seemed to be leaky, so I wanted to re-do that, just in case. Also, I couldn't really be sure of the part number, and R_J had said this might well be a 24V, and...

I had disconnect one lead of the diode in parallel with the relay's coil, so it was indeed bad. It's possible I myself fried it when I fried the trace.

There are no markings on ZD1. It occurs to me that I could pull and test ZD2, which looks identical, and it may be worth doing that anyway since, as mentioned in my prior message, I have already been wondering about whether or not it might have worked in tandem with ZD1 and thus suffered the same fate.

Thank you very much indeed!

Really impressed! Thanks! OK, I hope to get to it soon, and I will report back! Thanks!

Well, I had a mini-victory troubleshooting and fixing an electrical issue with a Whirlpool oven, but the ancient Cuisinart coffeemaker still has me in fits.

I installed the new 53AP3 chip, checked things over, and tried to flip it on. Still nothing . . .

So, it's back to the drawing board.

I am not detecting much voltage across the full bridge rectifier -- and yes, I did solder in a resistor to supply a load. I only see 0.6V which I think would correspond to the voltage drop of one of the rectifier's diodes. But, I probably don't know what I am doing ....

Thanks for that. I do have 5 used 53A3P chips in hand -- from Utasource. They came down from New Jersey. I forget what I paid but it was really cheap. And they look really good -- suspiciously good. We'll see what happens . . . Thanks!