Suitable replacement IC? .PCB - X_BFJSFANRE_RLED_V4

[ezenia]

Hello,

I am not sure where exactly to put this thread, so hopefully this is the best place.

I have a USB fan that has suddenly been unable to increase its speed. It's just stuck on the first speed. This fan has 3 speed settings. Each time you press the power button, the speed of the fan should increase.

The way the button works with each press is: Speed 1 > Speed 2 > Speed 3 > OFF

Speed 2 and 3 don't currently work any more.

I suspect the issue might be with what looks to be some kind of driver IC. It is a 16-pin and the fan power switch goes to this IC. The IC has no markings, so I can't find the exact part.

Does anyone know of a suitable IC replacement that can be bought? I've attached an image of what the IC looks like. If anyone has any advice on how I can check if this IC is definitely the problem, that'll be helpful as well.

[stj]

Re: Suitable replacement IC?

does the button still turn the fan on and off?

[sam_sam_sam]

Re: Suitable replacement IC?

What is the marking on the ic chip

[redwire]

Re: Suitable replacement IC?

Weird how the IC has a bunch of pins not soldered and sitting on top of silkscreen. Also, the 4R7 seems low for any pin on a SOIC-16.

Can you show us pics of the whole board.

[ezenia]

Re: Suitable replacement IC?

does the button still turn the fan on and off?

Yup. The button still performs those functions as normal. It just no longer increases the fan speed when I continue to press the fan button.

What should happen is I press the button and the fan comes on (speed 1). If I wanted to increase its speed, I press the button again. This should cause the fan to speed up (speed 2). If I press it again, the fan will enter speed 3 (highest speed). If I press the button one last time, the fan turns off (as it should).

Right now when I try to initiate speed 2 and 3, the fan does not speed up. The final press still turns off the fan as normal.

@sam,

There doesn't seem to be any markings on the IC. It's blank.

@red,

I've attached a pic of the whole PCB. The other switch on the PCB is for another function I haven't used. It's for some "water mist spray"

https://flyingtiger.com/en-gb/produc...-light-3048154

That's a link to what the fan actually looks like.

[ezenia]

Re: Suitable replacement IC?

Could the USB IC be responsible for the speed control issues? There is a 6-legged IC near the USB port. There's also some LEDs nearby. One is green and another is red. The green LED looks to be for when everything is OK and working. I've seen the green LED shining when I used the fan before.

When the fan is plugged into a power source and the fan is off (not spinning), I notice the red LED is faintly flickering red. I don't know if this is normal behaviour. When I turn the fan on, the red LED goes solid red. The green LED is still on as well.

The markings on the USB IC look to be "LPS BMCH1". I could not find anything about this from a Google search.

I did find this https://www.mouser.co.uk/ProductDeta...ym3GprBA%3D%3D which looks like it could be an IC like this. On the datasheet, it mentions a FAULT pin. Could the IC be detecting a fault of some kind and that's causing issues with the speed control?

[peter_]

Re: Suitable replacement IC?

Which connector is going to the fan ?
The IC near the USB port will be a voltage regulator. The black IC will be a cheap microcontroller. The fan speed will be controlled by a PWM signal. If you have a scope you can monitor the driving signal to one of the small transistors.

[ezenia]

Re: Suitable replacement IC? .PCB - X_BFJSFANRE_RLED_V4

The middle connector is the one for the fan. I don't have a scope unfortunately.

I did check the pins on that microcontroller IC and the upper pin on the left side of the IC has voltage that changes with the button presses.

On the first press (speed 1), the pin reads 1V. The 2nd press (speed 2) reads 1.4V and the 3rd (speed 3) reads 1.8V. I don't know if these values are good/normal, but this does tell me that something is happening. I followed the voltage to Q2. It's on the left pin. The lone pin at the top has 4.74V.

The voltage at the fan button is around 4.14V. This does not change. If I hold the button down, it reads 0V, but otherwise it just stays at around 4.1V.

Another thing I find odd is the behaviour of the red LED (It's the top one in the LED1/LED5 area). It's flickering red when the cable is connected, with the fan switched off. When I measure the voltage on the fan button, the red LED goes solid red. It also goes solid red when I turn the fan on normally.

I don't know what the supposed function of the red LED is, but I can only assume it's not for anything good. There's already an LED for power (it's green), so the red must come on when something is wrong.

[stj]

Re: Suitable replacement IC? .PCB - X_BFJSFANRE_RLED_V4

check all transistors, diodes and caps for shorts.
the chip obviously works,
it's probably using one transistor to vary the voltage to the motor and another to just turn it on and off.
the part with 5 or 6 pins is the usb charging chip,
too bad about those missing resistors R2 and R4, i suspect they are to activate intelligent usb powersupplies.

[stj]

Re: Suitable replacement IC? .PCB - X_BFJSFANRE_RLED_V4

btw, the picture is not clear enough to read the markings on the transistors,
but those inductors make me wonder if atleast one of those "transistors" is actually some type of voltage regulator.

[ezenia]

Re: Suitable replacement IC? .PCB - X_BFJSFANRE_RLED_V4

I've attached another pic of the PCB. Hopefully you can see the markings on the board more clearly. If not, I'll try to take another.

[ezenia]

Re: Suitable replacement IC? .PCB - X_BFJSFANRE_RLED_V4

check all transistors, diodes and caps for shorts.
the chip obviously works,
it's probably using one transistor to vary the voltage to the motor and another to just turn it on and off.
the part with 5 or 6 pins is the usb charging chip,
too bad about those missing resistors R2 and R4, i suspect they are to activate intelligent usb powersupplies.

I checked for shorts, but couldn't identify any.

[ezenia]

Re: Suitable replacement IC? .PCB - X_BFJSFANRE_RLED_V4

Do these voltages at U1 look normal?

This is with the cable plugged in and the fan being off:

Pin 1: 3.3V

Pin 2: GND

Pin 3: Around 4.2V

Pin 4: 4.74V

Pin 5: Can't get a stable reading, it's jumping between 015.0-070.0mV

Pin 6: 0V

With the fan turned on (first speed setting):

Pin 1: 0.670V

Pin 2: GND

Pin 3: 4.08V

Pin 4: 4.73V

Pin 5: 2.178V

Pin 6: 020.7mV

The pin values don't really change with the other speed settings.

[stj]

Re: Suitable replacement IC? .PCB - X_BFJSFANRE_RLED_V4

you said

I did check the pins on that microcontroller IC and the upper pin on the left side of the IC has voltage that changes with the button presses.

On the first press (speed 1), the pin reads 1V. The 2nd press (speed 2) reads 1.4V and the 3rd (speed 3) reads 1.8V.

so pin9 is speed control.
and pin1 is the on/off

what are all the connectors for?
i see 3 of them!

[ezenia]

Re: Suitable replacement IC? .PCB - X_BFJSFANRE_RLED_V4

The other connectors are for the water mist spray feature. I don't use that part of the fan. I've only ever used the fan itself which is the middle connector.

I am pretty sure the fan feels quieter as well. I remember this fan being quite noisy even on the first speed setting. Now it seems like it's quieter, perhaps it's running slower than normal.

I currently suspect something might be wrong with U1. The behaviour of the red LED is bothering me as well. I don't think it should come on when the fan spins, or be faintly flickering rapidly when the cable is plugged and the fan is off.

It makes no sense to have two LEDs for just power. The green one is meant to be on as I've seen it through the port when I used the fan. The red one though? I don't know if it's meant to be on or not.

[stj]

Re: Suitable replacement IC? .PCB - X_BFJSFANRE_RLED_V4

red is probably low-battery and/or used by the charger

[ezenia]

Re: Suitable replacement IC? .PCB - X_BFJSFANRE_RLED_V4

This fan isn't using a battery. One of the connectors is unused. I remember one of them was empty. I checked with the Google translate app and it says the connector near D1 is "Battery". I wouldn't think they'd add a charging circuit to a board that is not making use of the battery connector.

[stj]

Re: Suitable replacement IC? .PCB - X_BFJSFANRE_RLED_V4

the 6pin thing is a TP4057 charging chip

[ezenia]

Re: Suitable replacement IC? .PCB - X_BFJSFANRE_RLED_V4

Ah yes, looks like it is. The voltage at pin 3 (labelled BAT on datasheet) is present on the battery connector.

Any idea what the STDBY pin is meant for? When the USB cable is plugged into the port and the fan is off, I am not getting a stable voltage reading on this pin. Once I turn the fan on, the voltage on this pin goes to 2.2V. Is this normal behaviour?

Should the battery voltage also be present at the fan switch button? Since this fan doesn't use a battery, shouldn't the voltage here match the VCC pin (which is around 4.74V)?

[ezenia]

Re: Suitable replacement IC? .PCB - X_BFJSFANRE_RLED_V4

Another thing:

With the USB cable plugged in and the fan off, if I try to measure voltage on U2 on either pins that lead to the button switches, the red LED goes solid red and the voltage does drop slightly.

If I measure the battery voltage in another area (say at the battery connector or R7), I get a reading of 4.2V (it's not steady though, it keeps going from 4.2v to nearly 4.3V and then down again).

Once I try to measure the voltage at the aforementioned U2 pins, the voltage drops ever so slightly and is very stable (sits at a steady 4.14V). The fan isn't on though since the LED that tells me that remains off (it's next to the switch itself).

The battery voltage with the fan properly on drops to a steady 4.05V.

These readings aren't making sense to me. Something seems to be wrong somewhere. It explains why the fan is not speeding up and why it seems to be running slower than normal (evident by how much quieter the fan is).