Harman/Kardon Onyx Bluetooth Speaker - No Power

[Agent24]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

Go look at the file SPEC-BM153-V4.3_03122009.pdf I linked\uploaded. On page 3\4 it tells you which pins do what.

Pin 1 on the module is marked with a 1. In your photo, it's the bottom-right corner. From pin 1, the rest are numbered in an anti-clockwise fashion around the edge.

Pin 3 thus, seems to connect to R306 on the main board. According to the datasheet:
"Reset if low. Input debounced so must be low for >5ms to cause a reset"

So you want to check that Pin 3 is not staying low, as that would hold the module in a reset state and nothing would happen.

You should probably also check power pins, Pin 12, 13, etc to make sure power is actually getting to the module.

[caphair]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

How exactly do I check to make sure it's not staying low? Am I looking for a voltage at pin 3?

[Agent24]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

Yes, you need to measure the voltage at that pin. You will probably need to press the power button too.

In digital logic terms, low means a zero - or normally 0v, and high means Vcc\supply voltage (In this case, probably 3.3v)

To be 100% sure the signal is OK, you would need to ensure that during the power-up sequence, the reset line stays low for at least 5ms, then goes high (as stated in the datasheet) This would need to be done with a logic analyzer or digital scope... but that's probably getting ahead of ourselves...

[caphair]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

Ok that layout confused me with the dimensions? On each pin which are numbered

[caphair]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

Testing voltage at the reset pin it goes to 1v when power button pressed and doesn't change unless I release power button and then the voltage drops.

Also measured before the resistor going to that pin and get same voltage (to rule out that the resistor value increased)Does that mean it's staying low?

Also there is 3.3v present on the VDD pin 13 so it is receiving that voltage as well as 1.8v on pin 15 so that voltage is present as well.

[Agent24]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

Hmm... that does not sound right...

The BT module can work on 1.8v or 3.3v, and has its own internal 1.8v regulator, which it supplies through Pin 15, and which seems to be working. I assume that 1.8v regulator is powered from either Pin 32 or 34, or both. (Out of interest, what do you measure on those pins?)

According to the datasheet, the voltage at Pin 13 determines the operating mode. Since you measured 3.3v on the supply pin, Pin 13 - it seems to be operating in 3.3v mode. 3.3v CMOS logic levels require 2v-3.3v for a logic high, so 1v would not be considered a high in that case. In fact, 1v is barely at the threshold for a 1.8v logic high, which is 1.17v.

Can you take a close up photo of the area above the module where the trace from R306\C306 leads to R304, near Q301? And see what voltage you get on the each side of R304 too?

[caphair]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

Ok that's weird I went to measure again and got no voltages at same pins, measured battery and it was 3.8v so I plugged the charger in and now I have 3.25v on the reset pin as well as on both sides of the resistor you wanted me to check.

[Agent24]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

Possibly your probe did not make a good connection the first time. If you get 3.25v on reset, then that sounds normal. In that case, I'm out of ideas unless you have a scope to check the clock.

The only other thing I could think is giving it a manual reset while the button is pressed by shorting across C306 momentarily. In the event that C306 is open circuit and is not allowing the reset signal to go low for at least 5ms but this is unlikely...

[caphair]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

Ok this is weird I just measured again and now get 1v on reset pin, however now one side of R304 has 3.25v and the side going into R306 has 1v

Possible it's bad? Both sides measured 3.25v just a bit ago

There's also 1v on the lead of that surface mount transistor? That's above R304 the lead that's next to its label Q301

[Agent24]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

That is strange. I would have expected the reset line to be either 3.3v or 0v, never 1v. Perhaps R304 is going high or open, or something is partially shorted (C306 or Q301). Or perhaps I just don't understand the circuit function...

From what I can see:
R304 seems to be a pullup, probably to the 3.3v rail. C306 likely provides the debounce and the 5ms delay the datasheet speaks of.
It looks like Q301 is for pulling the reset line low externally from somewhere else, but what exactly turns it on, I am not sure. I've drawn a schematic of what the circuit seems to be.

What voltage you get on the base and collector of Q301? Compare these between when reset is 1v and when it is 3.25v and see if there is a difference.
For pinout, check the datasheet attached. (The Code W1A comes back to PMBT3904 which is a common part)

Also, can you measure the resistance of R306, R304 and R308?
Also, do you get any resistance measured across C306?

Can you post a photo showing the PCB tracks around Q301 with more light? I can't see where the tracks go near C317 and C318 etc.

EDIT (Mistake in Schematic on R308)

[fzabkar]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

Isn't R308 connected between base and emitter?

BTW, the pinout is BCE (left, tab, right).

T4 (D301) could be a 2.7V zener or a 1N4148, but it doesn't look like the latter. Perhaps it senses the battery voltage, but I can't see how it would work with Q301 to do this.

[Agent24]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

Isn't R308 connected between base and emitter?

BTW, the pinout is BCE.

Yes R308 is between B-E, I made a mistake the first time.
Q301 Pin numbers are not correct for SOT23, I think the program defaults to TO92. I've removed them. (Need lunch!)

[caphair]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

Ok I'm getting 0v at base (left pin) of Q301 and 1v on collector (tab) same 1v going into the reset pin.

Measurements
R304 - 14.2k ohms
R306 - 0 ohms - shorted or something in parallel with it shorted?
R308 - 220k ohms
C306 - 781 ohms

[Agent24]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

R306 may just be a 0 Ohm resistor, although why they'd use that, I don't know. Maybe they had something higher value there during prototyping and testing, and use 0 Ohm in production.
Resistors don't fail shorted, and there isn't anything in parallel with it that I can see, so it's probably supposed to be 0 Ohms.

If Q301 has 0v on the base, it should be turned off. Thus, it should not be pulling reset low.

BUT... If you are measuring only 781 Ohms across C306 (and incidentally, probably also across C-E of Q301) that could indicate a problem. Try measuring resistance across it again both ways (ie, swap your probes around), see if the readings change. Also might be interesting to see what you get both ways in diode mode too.

Also can you check if the Emitter of Q301 is connected to ground?

[fzabkar]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

Would it be worth isolating the reset pin at the PCB (by desoldering it) and then shorting this pin manually? This would also confirm whether the leakage (?) to ground is external or internal. Is this kind of leakage a typical failure mode of MLCCs?

[Agent24]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

Yes, I would personally try disconnecting the BT module, C306 and Q301, and check if the conditions change after disconnecting each one. However, SMT can be tricky and ideally you'd want hot air for this.

MLCC can definitely fail shorted, I don't know about leaky, but I suppose it's possible.

[caphair]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

What if I provide 3.3v to the reset pin to keep it high? Thinking of ways to avoid having to remove smt components lol but I could try removing them and testing as well, just curious if that would be a good test as well.

"BUT... If you are measuring only 781 Ohms across C306 (and incidentally, probably also across C-E of Q301) that could indicate a problem." I'm curious what the problem could be, shorted capacitor?

[fzabkar]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

Maybe C306 is leaky. I've seen leaky disc ceramic caps, but the only MLCC faults that I've encountered have been dead shorts. Perhaps that's because they have all been supply bypass caps rather than "signal" caps. A leaky cap across a supply would go undetected until it goes completely short circuit.

Another possibility is that Q301 may have a leak between C and E.

Would it make sense to place a 1K resistor in parallel with R304? This would pull the reset pin higher without risking damage to Q301 or U300.

[Agent24]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

Maybe C306 is leaky. I've seen leaky disc ceramic caps, but the only MLCC faults that I've encountered have been dead shorts. Perhaps that's because they have all been supply bypass caps rather than "signal" caps. A leaky cap across a supply would go undetected until it goes completely short circuit.

Or perhaps with the relatively high resistance of R304, the current through C306 is being kept low enough to stop it completely breaking down. Shorted capacitor biased in the leaky region?

Another possibility is that Q301 may have a leak between C and E.

Seems maybe more likely, would explain why the meter doesn't show 0 ohms across C306, which I would expect if it were bad.

Would it make sense to place a 1K resistor in parallel with R304? This would pull the reset pin higher without risking damage to Q301 or U300.

It could work, assuming the potentially bad part is only leaky. If it's properly shorted I would assume that it's unlikely to make a difference. Worth a try though, I guess.

Disconnecting\removing parts would be a more reliable test though.

[Agent24]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

What if I provide 3.3v to the reset pin to keep it high? Thinking of ways to avoid having to remove smt components lol but I could try removing them and testing as well, just curious if that would be a good test as well.

If you give 3.3v to the reset pin directly from the 3.3v rail you risk a potentially shorted part going up in smoke or just shutting down the supply. I wouldn't want to blow C306 if it is bad, burning ceramics can make nice holes in PCBs.

fzabkar's idea of lowering the value of R304 is probably a better compromise. You should be able to tack a standard resistor's leads across R304 fairly easily too.

"BUT... If you are measuring only 781 Ohms across C306 (and incidentally, probably also across C-E of Q301) that could indicate a problem." I'm curious what the problem could be, shorted capacitor?

Yes, the only things that make sense as I understand it, are that Q301 or C306 could be shorted\leaky, or the same could apply to the BM150 module itself, since those are the only 3 parts that seem to potentially provide any path to ground from the reset line.