Logitech Z506 power supply

[dj_ricoh]

hello
i got this sound system to fix for my friend but the problem is that i don`t rly know where to start.
i desolder like 95% of all the caps from the psu and its still doing the same thing
like here you can here a sound squishing
http://www.youtube.com/watch?v=C0O5p...ature=youtu.be

usualy the main speaker got that big serial cable that power up the psu .
maybe the cable(speaker broken), like the console from z5500? or the actual psu its broken.
p.s. i found a burn(black-ish) resistor 10 oHms replace it. at that moment i didn`t have a 10 and i place a 30 ohms but its still doing the same uff
any tip will be welcome just to know where to start dig.
ty

[Khron]

Re: Logitech Z506 power supply

"I desolder like 95% of all the caps from the psu and its still doing the same thing" - what exactly do you mean by that? You tried to turn on the PSU entirely cap-less???

Got any photos of the underside of the board? What's the chip controlling the whole PSU? I'm guessing it's near those two small caps on the top edge of the board.

Speaking of those two small caps, that's a starting point - replacing them (with some reputable brand ones). After that, check to see whether that rectifier diode is shorted or not.

[dj_ricoh]

Re: Logitech Z506 power supply

no! sry
i desoldered them and test it .
i don`t have a esr meter but my fluke 175 got farad function :-s
sry

[budm]

Re: Logitech Z506 power supply

Need to see the bottom side of the board, that 10 Ohms may be used as the fusible resistor. Can you see the P/N of the device attached to the heat sink?

[dj_ricoh]

Re: Logitech Z506 power supply

the resistor was in R2 spot.
the diods d1 d2 d3 d4 i desolder one leg and i check them and they all good.
i`ll try to check the transformer today because i saw it like move a little (desolder in time like a cold joint); i place it back but still the same.
i will like to test it but i don`t rly know i do know it got primary side and secondary side. i`ll research it today.

[Khron]

Re: Logitech Z506 power supply

Well, caps CAN retain their capacitance value, while their ESR goes up - they're "still" no good that way.

As i told you before - replace those two small electrolytics on the primary with some GOOD ones (Panasonic, Nichicon, Rubycon, National / United Chemicon) from a low-ESR series, and see if anything changes.

Also, check if that TO220-cased rectifier on the secondary isn't shorted.

[dj_ricoh]

Re: Logitech Z506 power supply

Well, caps CAN retain their capacitance value, while their ESR goes up - they're "still" no good that way.

As i told you before - replace those two small electrolytics on the primary with some GOOD ones (Panasonic, Nichicon, Rubycon, National / United Chemicon) from a low-ESR series, and see if anything changes.

Also, check if that TO220-cased rectifier on the secondary isn't shorted.

ok i disconnected the big (other mobo) board and the psu got a steady V.
no more beeping.
brb got a lot to check.
sry for the trouble

[budm]

Re: Logitech Z506 power supply

BTW, that 10 Ohms is part of the snubber circuit, you should replace it with same value, you also need to check the cap and the diode in that same area since they are also part of the snubber circuit to protect that SMPS IC.
"got a steady V" steady with dummy load also? Those two small startup/running caps should be replaced as mention.

[dj_ricoh]

Re: Logitech Z506 power supply

should be replaced as mention.

ty for the reply!
i change them; now i got another think that when i connect the speaker with the serial cable(with the power button, the voltage go nuts)
i open the speaker and tested the wires inside, maybe they are bad;
the cables are fine i don`t think the board from the small speaker has a problem because i look and search what cable(wire) its the power switch 2 and 7 so i put a wire there without the small speaker and the board when nuts again.


p.s. the price of the whole system its so small its not worth fixing it, but i feel that if i do manage to understand and repair it it will be like i pass a exam and will know more then now.

[dj_ricoh]

Re: Logitech Z506 power supply

i wanna see if this pt2325 got the right value and after i connect the controler speaker and it starts to blink what values does it have.
anyone got an ideea where to find this chip besides aswo cuz i need to make a account there and i don`t have.

[BraVa]

Re: Logitech Z506 power supply

Please help my!
values components : R13,R1,R2,D5
Thanks.

[lexwalker]

Re: Logitech Z506 power supply

ty for the reply!i change them; now i got another think that when i connect the speaker with the serial cable(with the power button, the voltage go nuts)
i open the speaker and tested the wires inside, maybe they are bad;
the cables are fine i don`t think the board from the small speaker has a problem because i look and search what cable(wire) its the power switch 2 and 7 so i put a wire there without the small speaker and the board when nuts again.

p.s. the price of the whole system its so small its not worth fixing it, but i feel that if i do manage to understand and repair it it will be like i pass a exam and will know more then now.

I think I spot a blob of degraded glue there? That black blob on the right in the first picture, hugging that big capacitor...

[momaka]

Re: Logitech Z506 power supply

This is a simple single output rail power supply. Since the power supply isn't working when connected to the audio board but otherwise appears to work fine when the audio board is disconnected, you need to check first if this is a fault within the power supply or the audio board. To do that, disconnect the audio board from the power supply and measure the resistance on the connector of the audio board where the power comes in. - If you do get a short circuit or very low resistance reading (under 10 Ohms), then there's a short on the audio board and that's where the problem is.
- If you do NOT get a short circuit or low resistance on the audio board power connector, then the problem is likely within the power supply. In that case, I would suggest recapping the entire power supply with good quality capacitors (except maybe for the main input 400V/450V capacitor - that one rarely fails).

Also, what is the voltage output of the power supply when it is not connected to the audio board?

[dj_ricoh]

Re: Logitech Z506 power supply

Try for replying.
Forgot I have bench PSU, just bought few weeks ago.
This morning when I was meditating after the coffee I realized that I could try to power without the internal PSU.
The PSU was faulty and install another one.
I tested to see if it runs on 12v and it does work.
I'm so happy that I manage to finish this stupid project.
I put new thermal compound and I close the box.
Thank you again.

[momaka]

Re: Logitech Z506 power supply

Good to hear you got it working .

By the way, the original power supply looks quite simple, so the problem will likely be easy to fix... if you want to troubleshoot it, that is.

[a.bug]

Re: Logitech Z506 power supply

Try for replying.
Forgot I have bench PSU, just bought few weeks ago.
This morning when I was meditating after the coffee I realized that I could try to power without the internal PSU.
The PSU was faulty and install another one.
I tested to see if it runs on 12v and it does work.
I'm so happy that I manage to finish this stupid project.
I put new thermal compound and I close the box.
Thank you again.

I hope this also resolves my Z506's issue too. How any amps does your 12v source supply to the unit?

[Th3_uN1Qu3]

Re: Logitech Z506 power supply

Had the same system in for repair today, looks like that power supply they put into it is absolute crap. Also looks like i won't have to post pictures since someone already did.

I did something different: Pulled the PSU (decided it isn't worth fixing), pulled the original AC power cord out and patched an Asus Eee PC power brick (19v, 2.1A) into the DC input of the board. Power brick stays outside. Works great. One advantage of this particular power brick is that it's got "soft" current limiting - when it is overloaded, it does not shut down, it just limits the output.

The original power supply puts out 13-15v, so 12v would be a bit on the low side. I first tested with an UPS battery and the speakers distorted pretty early. It's much better with 19v. The amplifier chips inside this thing can take up to 24v supply so 19v is no problem.

You could use a 3A or bigger power brick for more oomph, but with this pile of trash, i don't think it'll make too much of a difference. Looks like Logitech quality has gone way downhill.

Apparently the Z-506 replaces the X-530, which is a superior system in every way. 75W RMS... yeah right, when the power supply is 35W. All speakers driven, this thing will output 20W max. It's just barely adequate for a small room, but there are better choices for the price. The woofer is a joke, the sattelite speakers have those caps on the top to make you believe they've got tweeters... nope, they aren't tweets. Just for show.

[a.bug]

Re: Logitech Z506 power supply

Thanks for the reply Th3_uN1Qu3!
I'll be on the hunt for a second-hand (cheap but does the job) laptop power brick capable of 19V 2A.

Cheers!

[Th3_uN1Qu3]

Re: Logitech Z506 power supply

Just in case you stumble upon an identical one, the exact model of my Asus power brick is EXA0901XH. It's white and it originally had a tiny jack at the output. I got it for free because it was dead. Reason: Output jack was bent and shorted. Nothing wrong with the adapter itself.

I also found the blown part in the original PSU. Along with the visibly burnt resistor R2, the snubber diode D5 was also shorted, read 0.003v both ways. It was a FR207 (2A, 1kV, 500ns), and i decided to replace it with a BY399 (3A, 800V, 250ns). It should work now... Still pondering whether i'll put the original PSU back in or just leave this Asus brick. It depends on how lazy will i feel tomorrow.

Anyway, the reason why it dies is they picked the completely wrong type of PSU for the application. The power supply is a flyback type, which subjects the switching transistor to high voltage stress, that's why a snubber circuit must absolutely be used. To compound this problem, this PSU was most likely designed for a mostly continuous load such as a small laptop or DVD/Blu-Ray player, while an audio amplifier is a pulsed load, which at high volume varies from near zero to maximum power many times a second. If the feedback loop of the PSU isn't fast enough (and with just a zener on the secondary driving the optocoupler, it certainly isn't), this will cause voltage pumping at the output of the PSU, which will then reflect thru the transformer as high voltage spikes in the primary. This is likely what caused the snubber to blow.

[momaka]

Re: Logitech Z506 power supply

I'll be on the hunt for a second-hand (cheap but does the job) laptop power brick capable of 19V 2A.

Doesn't have to be exactly 19V and 2A. I'd say anywhere between 15V and 20V and capable of at least 2A should be fine. Many laptops use 19.5V power bricks.

In my experience, not all of them work, though. In particular, some just tend to have a very noisy output. Also, avoid anything that has a groud pin. Otherwise you may get some "interesting" noises at the output of your speakers.

I first tested with an UPS battery and the speakers distorted pretty early. It's much better with 19v. The amplifier chips inside this thing can take up to 24v supply so 19v is no problem.

Curious question... what amp ICs does it use?
I sure hope it's something capable of BTL configuration. Otherwise with 12V, you won't get much more than a watt or two at output with 8 Ohm speakers.

All speakers driven, this thing will output 20W max.

20W RMS isn't that little if you have some nice proper big speakers positioned at the right spots .