Almi's Logitech Z-5500 Mod (High-End upgrade for the speaker system)

[ramachandra]

Some of my thoughts:
 
The first thing you should do is to check the voltages when the system is off and when it is on. You need to find +18V and -18V and +8V in the D-Sub connector. Probably you find no +18V and the reg and the surrounding components need to be replaced.
 
Let the system run for couple of minutes and unplug it from the socket, and try to touch and find hot components. If there is a short circuit the energy converted to heat somewhere. Can be an OpAmp failed in short.
 
About the wire you found. It is probably created a short circuit to the ground, so it is possible your Sub not worked properly since the beginning. In theory the TDA amp maybe failed due to the constant connection to the ground, the built in short circuit protection reached the limit to take. If the amp have some sort of short circuit inside that can cause voltage drop so maybe enough to interfere with the requirements of the other components or even ruin them. For example the negative voltage regulator or the chip to turn on the system.

 

[Strider]

@Ramachandra
 
I didn't upgrade my Z5500 but still have a question about it, because it won't turn on anymore.
 
The last couple of months it was getting harder and harder to switch the Z5500 set to On. 
 
The red light under the on/off button on the control pod was visible, but when i clicked the button not happens, normally i can click 20/30x times, or i have to switch the on/off switch on the subwoofer, that normally helps to turn it on.
 
But now the red light under the on/off button on the Pod is not lighting anymore.
 
Any ideas what the main cause can be?

 

[ramachandra]

Toughs: The LM217 adjustable regulator is failed, need to be replaced. Possible reason: aging of the regulator and the 4700uF 25V cap near. Other option is failed bridge rectifier. AM152 on the newer version, KBPC1502 (3 blue 1 black wires connected) in the old Z.

 

[Strider]

Thanks for the advice! Where can i find this LM217 adjustable regulator?
And is there a way to test it without removing it?
 
 
I tested both KBPC1502s (I have the old version), and they both seem working fine. 

 

[ramachandra]

Near the 4700uF 25V capacitor, attached to the heat sink, like the TDA Amps. About half of the length comparison to the TDA's. The reg provide +8V, you can see on the image the pin 10 to check.
 
https://d1jesv1uvhg9i4.cloudfront.net/6/64/6409f5fe_z5500pinout.jpeg
 
Under load when the pod is attached to the system it may drop if there is a problem, so check it again if it seems OK without the pod first.

 

[Strider]

I checked the pin layout without the pod, and i don't have any voltage on the pins. 
 
Can you specify on the photo's where i can find it?
 
http://i68.tinypic.com/2yy4n6p.jpg
 
http://i67.tinypic.com/fdy1w5.jpg

 

[ramachandra]

 

[Strider]

 

 
Thanks! But gosh, that is a work to replace! I have to detach the amplifier from the heatsink. 

 

[Augusti]

Hey ; I have a system console Z5500 namely IC damage. CS 42526.
What I want to do, I want to replace the console with a preamp and accurate, but can not remove the amplifier from st-by.
The pin must be connected to the VGA jack to remove the amplifier from st-by. Thank you.

 

[CraXyOW3]

Hi, been searching this thread for the same or similar problem, but i have not found one.
My system is so far unmodified, but wanted to start modifying it, thou my center speaker is not working at all.
 
I saw the c104 smd component was "gone", nowhere to be found, can say it is missing as there are solder residue and all the other similar slots for the others have one.
So having the "c" marking i guessed it had to be a capacitor smd of some sort, tried to bypass it but then the fuse went immediately.
 
My question is, what value is the "c104" cap and is my TDA7294 for center output burned? ST's schematics points to a 22uF cap for output on pin 14, could this be the right value?
 
Appreciate any answers, thanks!
 
Center's area.
https://dl.dropboxusercontent.com/u/22235170/z5500/20160123_153501.jpg
 
Overview
https://dl.dropboxusercontent.com/u/22235170/z5500/20160123_171657.jpg

 

[Augusti]

C-104 =100 nF 

 

[ramachandra]

Augusti
 
If I understand correctly you do not know how turn on the Amp without the Pod. There are three options. Buy the proper cable on eBay according the PID of your Z, make one, or just solder the pins together inside and use the main switch for on/off.
From the PID 636 you need this connection. If you find it too loud add 50K resistors to the ground before the 20K for each channel. Replace the 20K with higher resistance for lover volume or less resistance to make it louder. Think between 0 to 50K for max and no sound. If you use pots make sure you get proper quality, crap will butcher the sound. Alps for example have good reputation. 
Before PID 636 it require an extra voltage regulator in the circuit to turn it on. This is what i found how to do it. The same thing with pots included.
 
CraXyOW3
 
If returning the missing SMD capacitor not solve your problem, i suggest to do the third mod first, replace the 6pcs OpAmps in the Pod next, if the problem still exist replace the TDA Amp and the electrolyte caps belong to it. This should work if the rest of your Pod is healthy.

 

[scratje]

Hi All,
 
Ramachandra,
My second modified Z5500 that i sold has been placed in a local pub in my hometown (i practice beer lifting over there) 

 
The music performance is very good but there is one minor problem that i want to fix if possible.
Due to the fact that the system has to play very loud constant, for at least 8 hours, 4 days a week, sometimes (a few times per month) the system shuts down (control pod led turns off black) and after a while comes back on, which i think is due to the thermal protection of the fixed voltage regulators 78M18A +18V and 79M18A -18V.
The max temp for these regulators is 125ºC and the current is 500mA.
Is it possible to change these regulators with a TO-220 1A fixed voltage regulator?
The max temp. for these is 150ºC and i can mount heatsinks on these ones.
 
The regulators are MC7818CTG http://pdf1.alldatasheet.com/datasheet-pdf/view/12490/ONSEMI/MC7818CTG.html and MC7918CTG http://pdf1.alldatasheet.com/datasheet-pdf/view/174024/ONSEMI/MC7918CTG.html
According to the seller at a local electronics shop, these regulators can replace the original regulators and due to the fact that they are 1A, they will not shut down due to thermal overheating that fast.
 
What is your thought about these regulators and do you tink it is safe to use them as an alternative?
 
 
As you can see, the originals still look good and not overheated
 
 

 

[ramachandra]

"the system shuts down (control pod led turns off black) and after a while comes back" It is more likely the LM217T regulator, because as i remember the two 18V reg only supply the OpAmps. There are few more regulators in the Pod for the other chips so if the Pod itself overheat maybe they can shut down the power too. The reason is i think the other regulators there are all hooked up to the +8V of the LM217T is, the big step down from 18V to have 5V for example, what is alone can produce lot of heat and i don't remember any big resistors to limit the current for them.
 
"Is it possible to change these regulators with a TO-220 1A fixed voltage regulator?" Yes it is. During my mass repair pastime i was using MC7818CT and MC7918CT while the proper replacement was on the way from Asia. The MC7XXX series are my favorite for OpAmps, I have them in my external DACs, they even beat the expensive SALAS regulator from certain point. Previously andro6600 come up with his way to keep TO-220 regs in place, what you can find here. Not a challenge for your talent.

 

[scratje]

Okay Ramachandra and thanks for your advice.
I used thermal pads  on the tda's and LM217T instead of the mica foil and thermal paste so this could be the problem with thermal shutdown.
I've read about the thermal pads, performing less good than mica with thermal paste.
I wil change the thermal pad on the LM217T back to mica with thermal paste now.
Maybe the problem wil be gone then.
 
 
the thermal pads i have used