Logitech Z-5500 Power Supply to Control Unit Repair help wanted

[Sci666]

Hi there,

i have a problem.
i have a Logitech Z-5500 Sound System with a small defekt.

this defect causes a higer voltage on the power line to the control pod unit.

normally on this line is 8Volts !   i have 13-14 volt on this line and if the control pod is off about 15volts

it seems that the pod can handle this higer voltage but this causes more problems like overheating and failing/gone LED lights

i attached a schematic i found in another forum.

i swapped out already the voltage regulator, the capacitor and the bridge rectifier but all of this has no effect. the problem remails exactly like before. (this circuit board is in the subwoofer)

the Pod unit is okay, i have another Z5500 and if i take the other pod its the same problem, if i take the other subwoofer everything is fine.

so what can cause the higher voltag ein this "small" circuit ?  i have no idea.

please help me

[TheMG]

Have you checked the two resistors connected to the ADJ pin of the LM217? A faulty resistor or broken solder connection there would cause the regulator to output the incorrect voltage.

From the voltage you are measuring, it sure seems like the unregulated voltage minis dropout voltage. In other words, the regulator is attempting to output a voltage higher than the unregulated input would allow. This is why I would suspect something with those resistors, since they set the output voltage of thee regulator. LM217 is an adjustable regulator.

[Sci666]

good hint !

i will check this and post again