Logitech Z506 power supply

[andris0]

Re: Logitech Z506 power supply

Hi!
I have a Logitech z506 . The power supply has spent a diode and a resistor . The diode FR207 resistance 100ohm . And there are none for me. It could be used instead of the 12v power supply ?
Thanks!

[Khron]

Re: Logitech Z506 power supply

Absolute worst case, if the bass speaker's connected with the wrong phase, you'll get a dip around the crossover frequency (which, in this case, i'm guessing might be anywhere in the 100-300Hz area?). If you find that music's sounding a bit "hollow", it shouldn't be too hard to reverse the two wires, i think

But considering these were cheap-ish to begin with, who knows, they might even end up sounding better with the sub reversed

[Th3_uN1Qu3]

Re: Logitech Z506 power supply

It won't really matter unless you have another subwoofer besides this. Phase issues, "nulls" only occur when there is more than one speaker reproducing the same frequency range. Either way will work.

[GeoX]

Re: Logitech Z506 power supply

A little update: That "burned resistor" was not burned, rather the blackish spot was (stubborn) degraded glue stain. The resistor measured fine (removed off the board to check and measure). Everything around that TOP258M I.C looks good (although the state/condition of the I.C is still unknown), except that failed diode at the turn-off snubber section. Then found 2 more failed diodes (RL205) at the primary rectifier section.

Thus decided to replace all the failed components I've found so far...

- 1x T3.15A 250VAC with 1x Wickman TR5/372 T3.15A 250VAC
- 2x RL205 (2A 1kV) with 2x RL257 (2.5A 1kV)
- 1x 1N4007S with 1x 1N4007

Then connect to the mains power and see what would happen. Aye, I'm expecting some components to get blown up again. Putting a light bulb in series would not be much fun...

Sure enough the same components replaced got toasted.

Looking back at the "path of destruction", one conclusion is that ceramic disc capacitor with the markings "68 1kV" (possibly 68pF). Could be breakdown at high voltage (encounter such problems before). And this capacitor is literally touching and/or pressed against the heatsink (not hard to see why this capacitor can fail). Also hardly any space to manouvere the capacitor away from the heatsink (plus squeezed in on the other side by the big main filter/smoothing capacitor), and the through hole is literally almost on the edge of one of the the heatsink sides...

Replacing that capacitor decision time. My options are...

#1. Use back a leaded through hole capacitor, which means the new capacitor will be literally touching the heatsink again! Besides ceramics, another option would be silver mica capacitor (rated for 150C).

Or...

#2. Use SMT ceramic capacitor (125C ones) which can be placed away from the heatsink, on the bottom of the PCB.

At the moment, option #2 looks interesting. What do you guys think?

Hey Im new here, I have a Z 506 which died (power supply pcb) a few years ago.
Finally got round to investigating and found a plug-in DC adapter with 15V 2A output. Works perfectly. Only snag now is polarity of the bass when reconnecting to main pcb... Do you think it matters? marking on pcb is vague! Hope you can help please, cheers

[Agent24]

Re: Logitech Z506 power supply

Do you mean crackling sound? Can you clarify if the sound is cracking or crackling, because they are quite different and could be caused by different kinds of faults. Can you make a recording of the sound and upload to somewhere (like soundcloud) so we could hear it?

Have you checked for bad solder joints? You may have a problem with some bad connection that expands and makes a good connection after it warms up.

[rayfloyd170]

Re: Logitech Z506 power supply

I have the same speakers, I replaced a dozen caps already. the problem with my z506 is that there is unusual cracking intermittent sound esp during cold start-up. could it be with the op-amps? I have checked about 50% of the filter caps by a capacitance meter and already replaced those already 10% below the rated capacity.

also I already replaced the potentiometer as I subject it to be faulty. but still the problem of cracking sound occasionally comes. after some time of running, the speakers gets fine.. I think there has to be some caps that needs to be replaced or what? pls help me (newbie here)

[Th3_uN1Qu3]

Re: Logitech Z506 power supply

OK, I don't need it anymore,it had a broken copper trace on bass volume..

Good job!

[stromm]

Re: Logitech Z506 power supply

I caved. Target online has the Z506 for $50US. The local store price matched, so I bought two.

I am starting to think this set is nearing discontinuation. None of the computer stores around here carry it and say they can't order more. With that and the price drops, the years I spent in electronic/computer retail makes me think they are short lived.

At least I can now play around with the failing set more leisurely.

[Joun]

Re: Logitech Z506 power supply

OK, I don't need it anymore,it had a broken copper trace on bass volume..

[Joun]

Re: Logitech Z506 power supply

P.S Do you know who the opamps are?The printing on them is very faint..

Nevermind, found it in this thread..

[Joun]

Re: Logitech Z506 power supply

Thank you for answer.I was hoping it will be you who answers since I can tell you have a lot of knowledge..
I can trace it back(it is a little hard but I can do it) and I have the datasheet of the amplifier ic.And I have instruments to check capasitors and signal presence(esr meter and oscilloscope).
I think the problem is before that somewhere in the volume ic or in the opamps ..
I will check it tomorrow and write back.

Thank you!

P.S Do you know who the opamps are?The printing on them is very faint..

[Th3_uN1Qu3]

Re: Logitech Z506 power supply

That's a fairly easy board. If you get no signal then it will either be the opamp or the coupling capacitors between the opamp and the sub amplifier. Trace the circuit back from the input pin of the sub amp and replace any capacitors that are in series with the signal, then report back. You only need a DMM with continuity checker (beeper) for this job.

[Joun]

Re: Logitech Z506 power supply

Since a lot of people are having problems with those speakers, here's mine:
A friend brought it to me because they didn't work at all..aOf course power supply was bad.
I replace it with another 15V supply and it seemed to be OK..
That happened 3 monthes ago.Yesterday he told me that the sub wasn't working at all so he brings it back and sure enough he is right.
I search it a little and realise that the amplifier ic for the sub doesn't get any signal in its input pin.
I can search it any more without its schematics so does anyone have it?
Or any other solution from someone with the same kind of failure?

Thank you.

P.S Other speakers are working,only the sub section is defect.

[Th3_uN1Qu3]

Re: Logitech Z506 power supply

It is recommended to scrape all the brown glue away. Also replace that little diode in the snubber circuit with a 3A 1000V fast or ultrafast recovery. That diode is the main point of failure in that power supply. A FR307 or HER307 will work, these can be scavenged from dead PC power supplies.

The diode is the black/grey component sandwiched between the two resistors and the green capacitor.

[Agent24]

Re: Logitech Z506 power supply

So if those are bad, would that cause audio to cut out after a few minutes?

Probably not. If the snubber components failed, the power supply, or at least the switching transistor would usually blow up. Since this hasn't happened, it's probably not the case. But you should remove that glue to prevent it from happening in the future.

Kinda wondering if I should just buy a new power supply board or if the issue is likely elsewhere...

The problem likely lies in the amplifier itself, but of course it could still be a power supply fault. That is why I suggested you measure the power supply output voltage and see if it changes when the audio cuts out. You might also want to check that the output voltage in correct to start with - a voltage that is too high might make the amp work for a while, but then overheat and go into some protection shutdown state.

[stromm]

Re: Logitech Z506 power supply

So if those are bad, would that cause audio to cut out after a few minutes?

Kinda wondering if I should just buy a new power supply board or if the issue is likely elsewhere...

[budm]

Re: Logitech Z506 power supply

That pix in post 74, that section looks like the RCD snubber circuit in the primary side so there will be high Voltage in that section.

[Agent24]

Re: Logitech Z506 power supply

Yes that's more of the glue. As you can see, the yellow part is more the original colour and where it has come into contact with the warm components it's turned brown and started to corrode their leads.

Those resistors are probably still OK aside from the corrosion (though removing and checking them would not be a bad idea) but in any case, you should definitely remove the glue from them as it goes conductive and in a power supply this can lead to significant damage if the glue is somewhere in the primary side\high voltage section.

In lower voltage areas the glue does not usually cause catastrophic failure, but can upset circuit operation and cause a fault condition anyway.

[stromm]

Re: Logitech Z506 power supply

Ah, good to know. Thank you for your patience. Even though I'm 45, I let my father (electrician by profession) fix all my electronics. Since he passed 4 years ago, I'm learning as I go now.

So I removed the power supply board and don't see any swollen caps, but I did find this brown stuff on these resistors. Is that more glue or should I remove and test them?

[Agent24]

Re: Logitech Z506 power supply

That black stuff is glue, and as long as it's only on the outside of the capacitor and not stuck to the leads, it's probably OK.

If it's on the leads of any components you should probably remove it, it can turn conductive over time and cause problems. Scrape it off with something, heating it with a hairdryer or similar (not too hot!) may help in removing it (can soften it a bit).