NAD 5325 CD repair attempt

[RichardM]

Hi All,

I thought I would try to repair an old NAD 5325 CD my brother left me. Just a hobbyist. At the moment you insert the disc and it seems to focus, starts to spin and then stops with "Disc" shown on the led display. I have scoped a number of points around the circuit as per the service manual but before asking questions about that I thought I would start checking some power supply voltages. BTW I think its a defective "pickup" but wanted to see what others thought of the volatages first. Could be many things based on my readings. I have attached an image of some of my measurements.

Basically I see "high" +12V and -12V rails ie. -12V is more like -14.3V ? I also see a lot of ripple even though I have recapped the unit. The frequency of the ripple either side of the bridge recifier is 100Hz which seems correct? but the positive side of the recitier(D604-604 junction) has 700mv ripple and looks like a relatively clean sawtooth wave. The Negative side is a not a clear wave and has 350mv peak to peak.

Any comments much appreciated. Are these voltages too high to be correct ? I am really not sure how this circuit regulates to get the 12V rails. Leaky diodes of transistors ?

Regards

Richard

[RichardM]

In hindsight this should be in the repair forum.