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flat-earther · 06-13-2025, 01:17 AM

Thanks sam_sam_sam,
The vac is already assembled, but I saw before that the cells are Samsung ICR18650-22P.
I already completed full charge after replacing the resistor and I monitored the battery voltage during the first charge and it stopped before 25.2V I think the last reading I got before it stopped charging was 25.16V then the voltage settled a bit lower, then I vacuumed for probably over 30mins and it was still going and had 1 out of 3 LED left when I turned it off, then I completed another full charge, so at the moment I think it's good.

flat-earther · 06-12-2025, 09:15 AM

Finally got a new resistor soldered. It's very small so was difficult, I stopped trying to make it better aligned since it is practically attached.

I verified with multimeter that it's connected to the traces.

After that I plugged in the charger and the 3 LEDs turned on, I think it blinked slightly different than before the resistor, but immediately all 3 LEDs stayed solid which is as if charging is complete, just like before the resistor.
I was disappointed, I thought there still was a problem...
I replugged the charger many times and same thing....

flat-earther · 06-10-2025, 11:39 PM

Good idea, but first I want to try if adding cap to battery rail works because it looks easier....

flat-earther · 06-10-2025, 09:31 AM

Thanks guys for your suggestions,

The component marked EAFC is the 32.768KHz oscillator, I think it's MC-146. one side is ground and the two pins on the other side are at 0.85V at standby,

I didn't find continuity from it to any pin on chips XR819 or AXP233.
On the other side of the board the chips B649SN and the covered one are BGA so can't test pins.

In standby I found few places at 1.8V, maybe adding a cap there would keep the time? IDK... everything is extremely small so I think I will connect a capacitor to some place on the main battery rail,...

flat-earther · 06-09-2025, 10:43 PM

Alright, I have an 0603 resistor kit on the way.

flat-earther · 06-09-2025, 07:04 AM

D1 diode soldered back.

Inductor repaired. I bent the copper wire down and soldered it to the pad.
...

flat-earther · 06-09-2025, 06:22 AM

I removed the diode D1, in diode mode it measures 0.575V one way, OL other way.
In resistance mode 68kOhm one way, OL other.

flat-earther · 06-08-2025, 11:54 PM

I tested all ceramic caps, didn't find any shorted. Ceramic cap C9 near motor wires is about 1 Ohm but the motor wires are soldered there so I think that's just the motor resistance.

All power disconnected, I measured in diode mode diode D1, 0.663V one way, 0.571V the other way. Is that okay?
...

flat-earther · 06-08-2025, 12:03 PM

All power disconnected, measuring Z5 in diode mode, OL one way, 0.725V the other way.

flat-earther · 06-08-2025, 11:11 AM

Disconnected all power from board, D13 in diode mode is open line one way and 0.217V the other way.

BTW while the inductor is essentially disconnected is there anything I should test in this state before reconnecting it?

flat-earther · 06-08-2025, 10:11 AM

Well removing that glue was extremely difficult. I used a 25W iron with sharp tip to pick it, then tweezers, and I destroyed the inductor by accidentally pulling the copper wire along with the glue with tweezers and the wire snapped.
I will need to try and resolder that wire back but it's so short I'm not confident in it, if that doesn't work I may unwind it one rotation to make it longer. I hope I didn't short the winding by scratching it with the tweezers.

From one side of the inductor to the end of the broken wire it measures 0.3 Ohms, is that still okay?...

flat-earther · 06-08-2025, 07:42 AM

Just to experiment, I have set an external power supply to 26V because that way I can see current draw on the power supply.
When I plug that power supply to the vacuum I see a very brief about 1A current draw and then it instantly drops to zero.

flat-earther · 06-08-2025, 07:36 AM

BTW I have manually charged the cells with an external charger so they wouldn't be empty. Right now the battery is at 24V.

How do you want me to check D13?

flat-earther · 06-08-2025, 06:47 AM

With the charger plugged in, black probe on ground, measuring voltage at input of the charging mosfet, I see it's constantly jumping between 27.5 and up to even 27.88V:

At the mosfet's output the voltage is constantly jumping between 7.6 and 8V:

At the mosfet's gate it's 27.2-27.6V:
Is such high voltage at the gate normal?...

flat-earther · 06-08-2025, 06:16 AM

Thanks.
My bad, that white is residue from when I cleaned the board with alcohol and didn't dry it well. I wiped it clean now, here's some new photos.

That resistor you circled measures 0.0 Ohms so it's okay.

I have labeled the wires connected to the board so it's clear what each is for:

Measuring the charger plug output without connected to the vacuum, it is 27.50V, a bit higher than labeled, I assume that's fine and since it's not under load....

flat-earther · 05-30-2025, 09:50 AM

The 16V bipolar junction transistor is NPN, and the 32V transistor is PNP.
On both measuring in diode mode between base and emitter in one direction is about 0.6V and OL in the other direction.

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