Dead Nutribullett blender

[peteblundoon]

Hi all,

The model is the Nutribullet Smart Touch Blender Combo 1500w, (Model NBF07520), also known as the NB T-15.
It is completely dead. I found that the earth wire spade connector was loose on the power board, made it firm and the power icon flashed on, the motor did a couple of revs, and then it died again.

There is 5vdc on the motor switching relay, and around 290vdc on the triac, but no volts on the logic/control board.

Has anyone had any experience with this model?

Cheers,
Blundoon

[wotnot]

no volts on the logic/control board

Likely the problem - image of said controller board?

[peteblundoon]

Likely the problem - image of said controller board?

Thank you for your reply wotnot. I have tried in vain to post a pic of the control circuit board but Austech just puts up a message that my picture file (jpeg) is invalid.

Do you know of a supplier of PCB's for this model of Nutribullet?

[wotnot]

To upload images, first upload to a free hosting site...ie; imgur or similar ... then post that URL link back here.

No, no idea where to get that PCB, but if I can look at it (both sides if possible) I can divine a method of checking it =)

[loopyloo]

Open "Post image"
Upload pic
Click copy - right end of "Thumbnail for forums"
Paste on this forum.

PS The image above is clickable

[Uncle Fester]

Hi all,

The model is the Nutribullet Smart Touch Blender Combo 1500w, (Model NBF07520), also known as the NB T-15.
It is completely dead. I found that the earth wire spade connector was loose on the power board, made it firm and the power icon flashed on, the motor did a couple of revs, and then it died again.

There is 5vdc on the motor switching relay, and around 290vdc on the triac, but no volts on the logic/control board.

Has anyone had any experience with this model?

Cheers,
Blundoon

Highlighted in red does not imply that the control board itself is faulty.
You need to first track down the power source that supplies the control board, wiring, connectors, maybe even a fuse somewhere.
However my gut tells me that a 'hidden' microswitch when the cup is removed, might be faulty.

[peteblundoon]

[wotnot]

Not immediately obvious where the low voltage power supply is -- need to view other side of PCB =)

[Uncle Fester]

There are 3 connectors with a pair of black wires each.
One or two of them will likely be for the microswitch(es) that activate the blender when the jar is firmly attached.
You can test on the plugs with a multimeter for continuity, do NOT have the power cord inserted of course.
Test with the jar attached, your multimeter should beep and read around 0 Ohms.
Test with the jar removed and they should be open circuit.
As said it can be just one or two switches.
Look on the side of the blender where the latches of the knife base go in. You should see a little pad or lever that you can push down with a small screwdriver and you might feel and hear a click. Try to confirm continuity by pressing the pad.
If it uses two switches you will find two moveable pads around the base
If the pad feels very loose and doesn't seem to click, then it could also be a problem with the mechanism that activate the switch(es) or the spring is broken inside a microswitch.

[wotnot]

I read the user manual ~ the cup detection microswitch has nothing to do with display/timer operations ; it only prevents the motor being energized, main control/display panel should have power at all times when switched on (standby mode with cup removed).

Typically how the circuit looks on these, is there's a low power DC supply rail (I'm imagining this is the 5vdc you found at motor relay), which feeds a 3.3volt LDO regulator, which in turn powers the MCU/electronics.

If a MLC cap or the MCU fails (goes short circuit) in the control side, the 3.3v LDO typically runs hot ...as in, it may not fail but (attempt to) supply 3.3volts @ maximum current limit (lets say 500mA) into a shorted component.

In that scenario, the low voltage rail might *not* be impacted ~ it will have been designed to provide enough amperage to satisfy the control/display section (lets say 1A)...so the LDO will sit there all day driving 500mA into a dead short, and the low voltage DC rail will be unaffected.

Of course, the LDO itself is at 100% duty cycle, so heat alone may cause it to fail ~ typically the circuit incorporates a fuse/fusible resistor somewhere, to protect against this happening.

....seems postimg.cc is broken.... yet again...(why I don't use it =)...when it comes back up, I'll add to this wrt your PCB pics...

edit:



Test for short condition across C1,2,10,12

[peteblundoon]

Update: I had to put this job on the backburner until now.
So far I have tested all the safety microswitches for operation and continuity all the way to the control PCB.

Because there was no power (5vdc) on the control board (see above), I removed it, applied voltage from my bench supply, and by shorting some pins on the connector
I got it to light up. The reverse side of the board has only LED's that light up under a mylar film connected with a loom to the control board and has touch sensitive controls on the exterior.

I found two faulty resistors on the power board (see below): R6 (open circuit), and the 1Kohm beside it (dead short), which is marked "L2" and with + and - polarity(?)
On the flipside I found an 8-pin IC with a hole in it. The damage obscured part of the printing and all that is readable are the numbers 3309.
I suspect that it is the driver for the LED's on the control board.
Can anyone supply a website that has circuit diagrams for this appliance?

Cheers

[wotnot]

PSU failure.... that's a bit easier . .. L2 is an inductor, not a resistor (why it reads short).
R6 is probably a fusible resistor, designed to pop if too much current is drawn.
The 8pin IC seems to have failed, causing the high current.
The number 3309 could be an LED driver, or, voltage regulator (letters before the numbers are key)...I doubt a blender has enough LEDs to require a dedicated driver ...so I'm guessing it's an LTC3309 ic
Picture of other side of PSU pcb would help me..
I doubt there's any schematics out there, but you typically don't need one for simple SMPS supply boards like this

[peteblundoon]

PSU failure.... that's a bit easier . .. L2 is an inductor, not a resistor (why it reads short).
R6 is probably a fusible resistor, designed to pop if too much current is drawn.
The 8pin IC seems to have failed, causing the high current.
The number 3309 could be an LED driver, or, voltage regulator (letters before the numbers are key)...I doubt a blender has enough LEDs to require a dedicated driver ...so I'm guessing it's an LTC3309 ic
Picture of other side of PSU pcb would help me..
I doubt there's any schematics out there, but you typically don't need one for simple SMPS supply boards like this

Thanks wotnot. I have attached a pic of the underneath of the PCB.
The reason that I would like a schematic is to identify components for replacement purposes - particularly the 8-pin IC. I looked up the LTC3309 - it appears to be a 10-pin.
I know that 'L' usually signifies an inductor, but why would the board be marked with polarity. The component looked like a 1Kohm resistor - brown, black, red with a silver band for tolerance,
and smelt like one - it had a small split in the side! It actually measured 0.6ohms.



Edit: I had another look at the board and solved the mystery of the polarity marking on L2. They refer to the electrolytic caps beside L2. What tricked me was that one of the +'s was printed right on the outline
which made it look like a -ve. I confirmed that by removing the resin from the cap positioned by the 7-pin connector and it was marked on the board the same way.

[wotnot]

Thanks, but damn those blue backed PCBs.... it's near impossible to see the PCB tracks.....and on top of that I can't find any schematics for these online...in fact, I can't even seem to be able to source replacement PCBs (or motors) for these things, all hidden behind the words of "please return to manufacturer for service"...what I DO find, is many reference quoting that repairing them is not cost effective, and buying a new one is the best option.

..yes, I noticed the polarity markings on the inductor, but because so many of these cheap chinese boards have crossed my bench, I simply remark to that sight with a "Pfffft... typical cheap chinese made PCB errata...again.." (I've seen polarity markings on ceramic bypass caps silkscreen =)

...most of it I can divine ....it's a control/PSU board....



That appears to be the 5v regulator circuit (however if this is blown, I wonder how you found 5v at the relay)

Best I can fathom from the connector markings.... RL1/RL2 relay on/off from controller PCB, 'zero' might be mains zero crossover point, TC could be temperature sense, PWM might be drive the SCR/thyristor to control motor speed, GND & 5V are obvious.

....it sux so hard that the PCB traces aren't visible, like tits on a bull....lets chase your supposition that U1 is something like a BP3309 ...consult the and come away with two observations ~ 1. this is not a typical application/circuit topology usage of this IC, and 2. max operating voltage is 22VDC (15~17VDC is typical). That infers the board circuit must be producing this low voltage DC rail from the mains AC input..

....it looks like that's the C9/R6/L2/D1 and 2 thruhole electrolytic capacitors circuit... but I can't see the tracks, you'll have to sus it yourself...should be mains active to dropper capacitor and resistor, inline inductor, halfwave rectification via D1, to smoothing electrolytics and to the VIN pin on the IC ..that's my guess. If it were on my bench, I'd replace R6, solder L2 back in, check/replace D1, replace electrolytics just because you know where they were made, remove U1, apply mains AC (without anything else plugged in) and expect to see a DC voltage on pad 6 for the U1 IC.... but...

...that looks more like a buck regulator output topology, just using the internal mosfet directly, seen this design a lot...(I wonder why =)...makes me question if this is a 'real' BP3309...or something else entirely. If this is the case, the IC blewup of it's own accord, or, an over current condition on the generated 5vdc rail (short somewhere) can make these fail (constant full load heat)...you can check the MLC caps thereabouts, the 2 schottky diodes, other stuff as a matter of course...

[bodeplot]

Hello Pete,

Good on you for trying to fix your blender instead of throwing it away. You are good to the environment. Lots of respect !

Unless an employee has leaked technical data, it is unlikely you will ever find a schematic for this throw away appliance. The closest thing you will get (if applicable) is to identify some of the ad hoc ICs and download the datasheets for them. Often those datasheets will offer a recommended circuit, or a test circuit. Manufacturers will most often use the datasheet circuit (which is the natural thing for an engineer to do from a risk/safety point of view). Using these datasheets, you can ascertain the schematic of your appliance. This is a bit of an industry trick to repair devices when no data is available.

When you say loose earth spade connection on power board, I assume this is an internal PCB in the blender ?. If so, then that is a weird spot to bond an earth. Appliance earthing is a safety feature, applicable to device surfaces that can be contacted by users. A theory: If a rail is floating on the PCB without an earth, and that earth is coupling a rail to ground (forcing it to ground), then it is quite possible that the loose earth could create back EMF on some of the power supply rails on the PCB if those rails are inductive (highly probable - appliance controls an electric motor). Digital ICs would not be happy with more than a volt or so. If back EMF is appearing on high impedance lines feeding those ICs, then the voltages would smash the absolute max voltage spec of the IC (this would be a good SPICE simulation to do).

Good luck

Bodey