PS28 SERIES III Bose sub, advice & service manual please.

[zen]

I don't have the head unit but have worked on Series 1 of these subs & they do power as a standalone unit.

Can anyone confirm that at least the standby LED should be on, with the series III?

[zen]

Re: PS28 SERIES III Bose sub, advice & service manual please.

Found the following video on YouTube & as in my case the 12-volt VS supply seems to be missing at pin 12 of the L6598D chip.

The engineer seems to tap off the supply from another source & uses a wire to link across to chip.

Not entirely happy with doing this, therefore will try to track the actual cause of missing supply.

https://www.youtube.com/watch?v=ixyN9sOurqo

[zen]

Re: PS28 SERIES III Bose sub, advice & service manual please.

Traced back from supply pin 12 of L6598D, through a few vias, which led me to the Emitter of an NPN transistor.

BASE 0V6

EMITTER 0V6

COLLECTOR 12V9

Removed & tested transistor which measured good. It's marked K1N U8.

Linked from collector to chip pin 12, which restored power supply operation.

Ideally, I would like to find faulty component.

[zen]

Re: PS28 SERIES III Bose sub, advice & service manual please.

Ahh now I see why he linked in the video.

Going back to transistor, the trigger to its base is not present to release supply to chip.

Traced the base back through many vias to opto U103 ( CNY17F-1 ), PIN 4 fact.

The 12V at pin 5 wasn't being switch from pin 1.

Traced pin1 of opto back again through many vias which led me to connector to main board, which must be where the issue lies.

No way am I going into the main after spending most of the day on this.

As a happy compromise I linked pins 4 & 5 of the opto U103.

All supplies now present.

Time to test, wish me luck.