Salvaging Logitech speaker system

I have a dead Logitech Z-680 5.1 computer speaker system that I was wondering about doing salvage work on, before discarding.

It consists of a subwoofer with all the amp circuitry and connectors for the main speakers on the back, and a dedicated control pod that connects to it using a custom wired DB9 connector.

The system stopped working and, since it was under warranty (and discontinued), Logitech simply replaced the entire thing with the current model (Z-5500) and does not want any of the old equipment returned. The old and new systems are electrically incompatible, so I just boxed the Z-680 setup and am triyng to decide what to do with it.

The electronics pod, which contains the controls, analog/digital inputs, Dolby/dts decoders, and preamp, powers up and detects and processes input signals appropriately. There is a power-on "thump" in all speakers when you fire the thing up, and the sobwoofer still has a little buzz coming out of it (that was normal), but after that ... nothing. Audio goes in, but not out. There is a special test mode that sends tones to all speakers for setting levels ... I hear nothing.

I'm not sure if the failure is in the pod or the main (audio) unit on the subwoofer, though I suspect the former. I opened the pod ... lots of surface mount chips, no visible fuses or resettable devices. Not user-serviceable.

The subwoofer has this huge metal cage bolted on the back which contains the audio amplifier circuits. I'm pretty sure the DB9 input on the back contains the 6-channel preamp output from the control pod. I was thinking of trying to send some test signals into the subwoofer's input socket, 2 pins at a time, until I figure out whether any of them elicit audio output from the speakers. Perhaps I can salvage the subwoofer and simply hook a line-level audio cable to whichever of the two DB-9 pins gives the desired effect.

Comments/suggestions? Thanks.

Reply to
Mike S.
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I suspect the problem is something simple, cracked solder joint at a connector, this might be a good opportunity to practice repair as a speaker system is relatively simple and safe to work on.

Reply to
James Sweet

Most of the busted speakers I've seen had mechanical problems. Banged the volume control and broke it. Banged the signal conector and broke it. Dropped and cracked the circuit board. You need either an oscilloscope or a signal injector. mike

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Reply to
mike

I don't think I've ever used either to repair speakers, usually the problem is pretty apparent once you get it apart. A walkman is useful for supplying a signal though, a DMM is usually sufficient for tracing.

Reply to
James Sweet

Reply to
Mike Berger

A *finger* is often enough to supply signal (although the walkman is higher-level, more stable approach). Touch an input and listen for hum. Another (working) powered speaker is useful as a signal tracer (protect the input with a small capacitor).

A DMM 'good enough' for the above can be had for $10 or less, and will come in handy in many other situations.

jak

Reply to
jakdedert

If you're testing *unpowered* speakers, yes. Otherwise, the output is entirely adequate. Shuffle down to your local pawn shop or even thrift store, and pick up a walkman for less than $5...not expensive at all...or particularly delicate for that matter.

But if you're concerned re: the above, buy a signal generator (not less expensive)...or a $1 (Dollar Tree store stock) FM radio.

jak

Reply to
jakdedert

Thanks, I think that might be the safest initial move. Remembering that one of the pins also supplies POWER to the control pod, I figured I'd test things out with a DMM first, and cross off any pins that have voltage coming out of them.

I've looked around and Logitech seems to have refused previous requests for pinouts of the input connector; though some have disassembled the subwoofer to fix internal rattles, nobody has bothered to map the input port. Opening this thing is such a bear that, given the choice, I'd throw it out rather than invest that much time if poking around from the outside doesn't yield anything.

Thanks for the ideas, folks.

Reply to
Mike S.

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