Need assistance, speaker system repair (Logitech Z5500)

[TheUnnamedNewbie]

And for a device that costs 2,50€ at a trustful store I wouldn't think twice save one or two bucks and risking other unforeseeable risks.

I have to agree with Twoflower - this isn't a obsolete/old part not available from other sources. If you can get it from a trusted supplier for 2.5 euros, why rist it?

[LeWidget]

Thanks gus

@Twoflower: I contacted Element14 and they said the sheet was indeed 150x150mm. I think I'll just grab one of those and replace all thermal insulation rather than mixing, that was they all line up.

I also ordered / received my replacement IC, ended up getting the 95' 80W, interested to see how it all goes.

Regards,

[LeWidget]

[update] So I got around to getting the sheet. Going to replace all the pads on the IC's ... just wondering, should I use thermal paste on them? (both side of the pad?)

[Twoflower]

No paste at all. As the material is flexible it replaces both: The mica and the thermal paste. But after mounting you should doublecheck that the amps are pushed with some pressure against the pad and mounted flush to the heatsink.

By the way the Mica sheets require very little thermal paste on both sides as the paste is used to fill the gaps of the surface of the transistor/mica and mica/heatsink. Only very little would be required.

After a short function-test you should observe the temperatures of the transistors to check that they won't get too hot.

[LeWidget]

Thanks Twoflower  

After a short function-test you should observe the temperatures of the transistors to check that they won't get too hot.

Is there a good way to test if it's too hot, without one of those laser temperature guns ?

[Don Hills]

...
Is there a good way to test if it's too hot, without one of those laser temperature guns ?

Put your finger on it. If you can't leave it there, it's probably too hot.

[Twoflower]

That trick with the finger works quiet well. Just be careful with temperatures above 60°C. This is the the temperature were proteins disintegrate. Pro tip if you can hold your finger very long on it it's below 60°C.

I would say that this is also a reasonable maximum temperature range for the amps.

[peteb2]

I'm going to add a couple of pointers with this piece of mass-produced kit that i experienced 1st hand dealing with... Background: i have been servicing gear for over 35yrs so to some extent i have 'seen it all'. Without being too rude the quality and workmanship of the product and it's final assembly is a bit to be desired... (I guess that's how costs are cut to the minimum).

The last thing OP you need to check before buttoning up your repaired unit is to 100% be certain the soldering of the two big smoother caps is REALLY GOOD. The unit i had the joy of meeting had cracked open all 4 contacts to the PCB and the owner talked of sound system working perfectly but at high volume it would suddenly  "making a noise fit to wake the dead'!... (yes unsmoothed +Vcc being feed to those chipsets just has to be a formula for disaster)...

Like the rest of the Amp, i suggest putting a bit of hot-snot glue around those big smoothers at their base so they can never wiggle on the solder connections again.

Finally when you button the thing up you need to really re-seal all the cabinet/enclosure surfaces so there will be zero chance of a whistle and hiss effects from the air being 'pumped' by the sub.

Just my 2 cents worth. 

[Dannyx]

Sorry for replying to such an old thread, but I was just curious: did you ever get these back and running ? I was curious what happened to the new IC you put in - did it work, did it blow ?