Help Diagnosing/Repairing Logitech Z5500

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scottycam

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Joined 2013
I have searched the net for ages to try and find a similar problem to what I have but have not found anything.

I am familiar with electronics and know the name and basic usage of most components so I thought it would be fun to try and fix my logitech z5500's, however lack the experience and understanding of amplifiers to find the issue myself.

The Problem:

My system still turns on and works perfectly for anywhere between 30 seconds to a minute. I can turn them up full and almost lose my hearing but they still give off a flawless sound, for the 30 seconds.

After a the 30-60 seconds the system basically freezes, the control pod shows all black squares. If I unplug the control pod and plug it back in (leaving the amp powered on) the control pod is still just frozen, displaying all black squares.

If I unplug the control pod before the amp freezes (say 10 seconds after turning it on) and plug it back in the control pod still works fine and i can play music/sound for another 20 seconds or so, then freezes.

If I leave the control pod unplugged and turn the amp on via the switch on the back and wait a few minutes then plug the control pod in it just displays all black squares and will not work.

So what I gathered from the above testing, the error is all within the amp itself. My best guess is that it has something to do with the amps power supply but am unsure how to test this.

Anyone got any ideas how I could trouble shoot finding the error, I am confident I can replace any components on the board itself but need help finding the error.

Every time I turn the power off to the amp and back on I can use them for another 30-60 seconds.

I have had a decent look over the board already but found no burnt spots or any solder connections that look dodgy. Plus after it freezes I feel around the board (after unplugging the unit from power) for any heat, nothing is remotely warm, all transistors are cool.

Any help or input would be awesome,

Thanks,
Scott
 
A

adsada

Member
Joined 2017
scottycam said:
I have searched the net for ages to try and find a similar problem to what I have but have not found anything.

I am familiar with electronics and know the name and basic usage of most components so I thought it would be fun to try and fix my logitech z5500's, however lack the experience and understanding of amplifiers to find the issue myself.

The Problem:

My system still turns on and works perfectly for anywhere between 30 seconds to a minute. I can turn them up full and almost lose my hearing but they still give off a flawless sound, for the 30 seconds.

After a the 30-60 seconds the system basically freezes, the control pod shows all black squares. If I unplug the control pod and plug it back in (leaving the amp powered on) the control pod is still just frozen, displaying all black squares.

If I unplug the control pod before the amp freezes (say 10 seconds after turning it on) and plug it back in the control pod still works fine and i can play music/sound for another 20 seconds or so, then freezes.

If I leave the control pod unplugged and turn the amp on via the switch on the back and wait a few minutes then plug the control pod in it just displays all black squares and will not work.

So what I gathered from the above testing, the error is all within the amp itself. My best guess is that it has something to do with the amps power supply but am unsure how to test this.

Anyone got any ideas how I could trouble shoot finding the error, I am confident I can replace any components on the board itself but need help finding the error.

Every time I turn the power off to the amp and back on I can use them for another 30-60 seconds.

I have had a decent look over the board already but found no burnt spots or any solder connections that look dodgy. Plus after it freezes I feel around the board (after unplugging the unit from power) for any heat, nothing is remotely warm, all transistors are cool.

Any help or input would be awesome,

Thanks,
Scott
Click to expand...

Hi Scott, sorry for bumping this really old thread, (I figured its ok as I would otherwise create the exact same thread question), plus im pretty desperate...

I have this EXACT issue, did you ever figure out what it was caused by?

many thanks
 
A

adsada

Member
Joined 2017
basi said:
I will say to check the voltage regulators inside the control pod.Inside u have 3 lm317 for digital,lcd etc... check all of them.
If they work then check regulator inside subwoofer the one that feeds the 8 v line.
Click to expand...

Im almost certian its the subwoofer at fault, I dont have a volt meter but I might get one...

I found this thread scottycam wrote after this thread where he highlights it as an amp chip?

http://www.diyaudio.com/forums/chip-amps/230500-replacing-tda7294-tda7296.html#post3378963

does that make sense?

many thanks for your help
 
A

adsada

Member
Joined 2017
basi said:
]
Click to expand...


Ok so I just spend this morning taking it apart and checking out the pcb in general. So the regulator seems to be reading 6 1/2 volts, but as I was doing this I noticed smoke coming off the board. It seems the resisters at R21 and R22 are burning, and they're roasting hot.

Even more odd, the fault is different how, the pod no longer craches, it works and then after a minute the sub speaker produces a noise which gets progressively higher pitched :confused:

So very odd, do you know if there is a circuitry diagram floating about?

Many thanks for your help :)
 
A

adsada

Member
Joined 2017
basi said:
Pls if you don't know how to fix this basic stuff give to someone who know before more damage is done.

Tda's must be in standby or must be heatsinked if they are turn on .Green wire of star grounding must be grounded with input and that's chassis.
Click to expand...


Ok...whilst its true Im not an expert I do know the basics, of course I made sure it was still all earthed, and the amps are still on the heatsink....really your patronising tone isn't appreciated and if you're going to keep being so arrogant I'd rather not get your help

cheers
 
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