Harman/Kardon Onyx Bluetooth Speaker - No Power

[Agent24]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

I did a continuity test and seems one leg of the switch connects to power "a" and another leg of the switch connects to power "b"

Is that what you meant?

Yes, and now we start to get a clearer picture.

So, it seems point Power_ButA supplies power to the button. When the button is not pressed, power does not flow through it, so point Power_ButB is at 0v.
When the button is pressed, current flows from Power_ButA, through the switch, and into Power_ButB, bringing it high.

To do something useful, Power_ButB will be connected to the input of some other circuitry, to perform some task related to power on.

What you probably need to do now is follow the trace(s) from Power_ButB and find out where it goes and what it's supposed to be activating. Then we need to look at what it gives power to when pressed and see if that is doing what it should be.

Also when I tried powering with a power supply set to 4.1v across battery terminals on the board, at first initial pressing of the power switch it draws 334ma then drops to 30ma with power button still being pressed

That big current draw is likely a secondary power supply (one or more of those DC-DC converters) kicking in and a capacitor charging up or such. How long does it draw that amount of current for?

[caphair]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

Probably a quick second, enough for it to display on the amps side of my power supply

[Agent24]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

Probably a quick second, enough for it to display on the amps side of my power supply

It's hard to say, I don't have enough experience and we don't know how the circuit here works, but while it may just be an initial power-up inrush current - it could also be that something is shorted and what you're seeing is a high current spike before one of those DC-DC converters goes into shutdown.

Again, we need to look at what could be potentially 4 different power supplies on the board, find out what they are, and ensure they are working correctly.

Another question too.. do you get that 4v on Power_ButA when using the external power supply and the battery disconnected?

[caphair]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

No voltage with charger connected and battery disconnected. No voltage change when power button pressed either

[Agent24]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

No voltage with charger connected and battery disconnected. No voltage change when power button pressed either

That could be part of the fault. I would expect that point to receive power with the external supply plugged in, unless it has some way of detecting the battery being disconnected and refusing to work, which seems a bit unlikely.

Let's start tracing the 19v through the board. I'm guessing it's first filtered through the large dark blue capacitor next to the black header, J600. Possibly it also passes through L606 first.

The large SMD Diode next to that capacitor is probably also involved... does power go through it?
Also check if power gets through the 2 zero ohms resistors nearby, R609 and R610.
I'd also check the small SMD inductor near J600, L703.

[stj]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

are there parts on the back of the board?

[caphair]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

I posted a pic of the backside of the board in my third post

[caphair]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

A friend suggested maybe the battery thermal circuit is kicking on so he had me try powering the device on with middle sensor terminal disconnected, and my adjustable psu hooked in to slowly adjust voltage and see if anything changes.

Well with the psu hooked in to that terminal and original battery +/- wires in place my psu read 2.5v with all the dials at 0. What's up with that? Adjusting it yielded no results in power on

[Agent24]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

I don't know for certain how the thermal sensing circuit works but as far as I know it's mostly just a thermistor. I fail to see how disconnecting it would yield any useful results, as the resulting input voltage to the thermal sense circuit would probably become either 0v or rise to Vcc, and would likely be interpreted as an extremely high or low temperature value - in either case the thermal circuit would probably panic and go into shutdown anyway.
But, if disconnecting that wire is a common trick which does actually work though, I don't know about it. Hopefully someone else has more knowledge on that. I would have thought you'd need to fake the correct voltage or signal output to fool the circuit into thinking the battery was at normal temperature.

I'm not entirely sure what you did? You powered the device from the bench PSU via the battery connector? Did you have the battery or 19v PSU attached also? If not, I can't think why there'd be a voltage reading if the PSU was set to 0v either.

I still think you need to verify the onboard power supplies and\or trace where the power button signal goes to.

[caphair]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

I was trying to trick the thermal circuit of the battery by using my psu on that lead and trying to adjust voltage through psu just to rule out possibility it was the issue causing shut down.

But my psu read 2.5v when I had it connected to the thermal pin on the board which puzzled me since all dials were at 0v

I'll have to try tracing power when I have more time I'm just confused exactly where to look. Do I need data sheet of all the ics?

Also I noticed if I have battery disconnected for a while and connect and try powering on the power led momentarily flashes where as any attempt to power on after that it doesn't light at all. Maybe capacitor failure?

[caphair]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

Ok so with just the charger plugged in I am getting voltage to the power button. It's 4.25v and when power pressed it doesn't change but power "b" goes from 0v to 4.25v

Also at the battery terminals there's 4.48v so we know voltage is reaching that to charge the battery.

All the 0 jumper resistors are not open. I traced the 19v from charger going to towards the left side of the board, the circuitry on other side towards battery connector must be to step it down for charging. The 19v might be what's needed to run the amplifier.

Right now I don't know what else to check or what the voltages should be?

[Agent24]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

I was trying to trick the thermal circuit of the battery by using my psu on that lead and trying to adjust voltage through psu just to rule out possibility it was the issue causing shut down.

But my psu read 2.5v when I had it connected to the thermal pin on the board which puzzled me since all dials were at 0v

If you had the battery plugged in at that time, you were probably measuring some voltage coming from the thermal circuit that was being powered from the battery, I'd guess.

As far as I know there are two thermal circuits. One inside the battery protection circuit (if it has one) which would disconnect the battery on abnormal temperatures, and another inside the amplifier which will read the temperature output from the battery and shutdown the amplifier if the battery starts getting too hot or cold.

The idea of ruling out a bad battery by bypassing the output from it is a good idea for a test, but you need to know what signal\voltage the amp's thermal monitor circuit expects to see from the battery so you can be sure you're giving it the right input. Otherwise if it still doesn't work, you don't know if it's because you didn't give it the right input, or if the monitor circuit is faulty.

I'll have to try tracing power when I have more time I'm just confused exactly where to look. Do I need data sheet of all the ics?

Yes. Post the datasheets or part numbers of all the ICs here. We can find out what the ICs are, hopefully what kind of voltages we expect to see, and then do some checks to see if each one is doing what it's supposed to based on what the datasheet says.

Ok so with just the charger plugged in I am getting voltage to the power button. It's 4.25v and when power pressed it doesn't change but power "b" goes from 0v to 4.25v

Also at the battery terminals there's 4.48v so we know voltage is reaching that to charge the battery.

All the 0 jumper resistors are not open. I traced the 19v from charger going to towards the left side of the board, the circuitry on other side towards battery connector must be to step it down for charging. The 19v might be what's needed to run the amplifier.

Right now I don't know what else to check or what the voltages should be?

Investigate the ICs as mentioned earlier. Once we know what they are we might get more ideas of what voltages should be present and where.

If the Amplifiers run off 19v then there has to be a boost converter somewhere to power them when running from battery. (You could verify that by taking the heatsinks off, reading the part numbers and looking up the datasheet for them. Their datasheets should say what their normal operating voltage is)
Their datasheets will probably also tell you which pin is Vcc, and you can trace that and find where it comes from. Probably it will lead back to one of those DC-DC converter circuits.

Without a schematic it's a matter of finding out information about ICs through their datasheets, tracing out what is connected to what, and using theory etc to work out what voltages should be found on various IC pins, then checking them and seeing if the readings you get make sense.

So at this point it's a matter of trying to figure out what voltages are expected, since we don't yet know and there's no schematic to tell us.

One thing I did notice is that there is a pin marked '3.3v' next to the power button pins. What voltage is measured there? What does it connect to?

You could also have a try at tracing the power button output to see where it goes and investigate that angle.

Also I noticed if I have battery disconnected for a while and connect and try powering on the power led momentarily flashes where as any attempt to power on after that it doesn't light at all. Maybe capacitor failure?

It's very hard to say what might cause that given how little we know of the circuit. But that kind of 'try once and latch off' behavior is what a protection circuit of some kind would do, so perhaps something is detecting an issue and shutting down. Then it requires a complete power-down with battery removal to reset it so it will try again.
Of course, it could be something entirely different.

[caphair]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

Ok so I was taking random voltage measurements and I noticed something. These two circuits are similar, maybe for the amp? Anyway I noticed the top one has voltage readings while the bottom one didn't have any when I proved same locations. This was also done with power button held in. The ic numbers are 54331 Which is a step down buck converter, but not sure if they're both supposed to be working at same time or not?

[Agent24]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

I have no idea if they should both work at the same time or not either. But we can hopefully figure it out...

OK, looking at the datasheet, that chip needs 3.5v to 28v on the input (Pin 2) and also the Enable pin, Pin 3, needs to be at least 1.25v for operation and either left floating or set by resistors.

In this case it looks like it is set with resistors:
R703 and R705 handle the enable Pin for U700, and R602 and R605 for U600.

Pin 8 of the IC is the output. There you should see a pulsed wave if you measure with a scope or probably some voltage if you check with multimeter. You should check both sides of the big inductors (L600\L700) to ensure power is getting through those.

Can you measure the voltage on all pins of both ICs and write down what you get for each one?

[caphair]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

Just reading this now and currently at work so I'll respond going off memory.

I do get voltages on most pins of the top ic and no voltages on any of the pins on the bottom one. This is both with power pressed on or off

[Agent24]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

From what I see on the board, both of them have their enable pins tied through resistors to the supply pin, so they should be enabled and working as soon as they get power. If one of them is not getting power, I guess you need to trace back its power input Pin 2 and see where it gets its power from and why it's not.

Might also be interesting to try trace its output and see what it supplies.

Additionally, if you can figure out which resistors are the feedback resistors (there's an example circuit and formula in the datasheet) you can calculate what voltage it should be outputting and then check that the working one does in fact output the right voltage.

[caphair]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

Ok, suppose those circuits provide B+ and B- to the amp, would they both still be on at the same time?

[fzabkar]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

It would help a LOT if all the chip markings were listed, including those under the sticker, otherwise we're working in the dark.

That said, ISTM that the amp would not require separate B+ and B- supplies. In fact we would need an inverting regulator to generate the latter. Instead we could get by with a single, boosted B+ supply. I believe that is the function of D702, L702, Q701 and U702, ie a boost converter. R728 appears to be providing the current sensing. The cathode of D702 (C726 - C731) appears to be the boosted output voltage.

[Agent24]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

And if an amplifier needs a -Ve rail, then yes, both it and the +Ve rail need to be present at the same time, otherwise you're going to clip off half the signal at best.

[fzabkar]

Re: Harman/Kardon Onyx Bluetooth Speaker - No Power

AFAICT, each speaker is driven from two amps in a full bridge configuration. That only necessitates a single supply, as is the case for most (?) car audio amps.

Fig 4B in the following article shows a dual supply but it could just as easily be biased for a single supply:

http://sound.westhost.com/articles/pwm.htm

In a dual supply configuration one terminal of each speaker would most likely be grounded, as in Fig 4A.

I expect that one of the "6R8" supplies would be responsible for the +3.3V rail. A continuity test between the 3.3V test point and each of the 6R8 coils would confirm this. A +/-3.3V rail could not possibly provide 15W into 4 ohms, as stated in the spec for the speakers, so this would again point to the boost converter as the supply for the power amps.