Pismo External Speaker Noise

[Krevinek]

I recently acquired a Pismo that was dead for quite a few months. I managed revive it without having to replace the logic board, sound board, power board or processor, which is good news. Here is the bad/annoying part of the machine:

If I plug in external speakers, I get a great deal of static noise (similar to tuning a radio if I turn/spin the connector). These speakers worked fine on the Lombard and 8600 I have used. If I use a pair of headphones, I don't get the static noise at all. If I use the internal speakers, no static noise either. Sound playback sounds pretty darn good except when connected to these external speakers.

I am thinking the noise is being caused by the amp in the laptop and the amp in the speakers being out of phase or something similar and introducing noise, and I have a feeling I will want to replace the sound board at some point in the future to fix this. Am I correct? Anyone else stumble across this problem?

Additional: Another unusual thing about this is that if certain sounds play, the static disappears for awhile, and then after a period of time, the static returns (as if the sound board is 'put to sleep' after a few seconds of no sound and puts out minor noise which the external speakers catch and amplify).

 

[DeltaMac]

An out-of-phase signal is not likely to cause a 'static' type of noise. The same amplifier in the laptop is used with headphones, so I would first try another set of external speakers. Borrow a set to test. If there is no noise with another set of speakers, then you can assume that your speakers are faulty. The connector from the speakers into your powerbook would be likely, and could be something as simple as not seating properly (the design of the plug not completely seating in the powerbook connector)
Or, the connector in the sound card is slightly worn, some connections work OK, but not everything.
The good news is: you could bypass your sound card completely, and use a USB audio connection, such as an iMic, to connect external speakers.

 

[Krevinek]

An out-of-phase signal is not likely to cause a 'static' type of noise. The same amplifier in the laptop is used with headphones, so I would first try another set of external speakers. Borrow a set to test. If there is no noise with another set of speakers, then you can assume that your speakers are faulty. The connector from the speakers into your powerbook would be likely, and could be something as simple as not seating properly (the design of the plug not completely seating in the powerbook connector)
Or, the connector in the sound card is slightly worn, some connections work OK, but not everything.
The good news is: you could bypass your sound card completely, and use a USB audio connection, such as an iMic, to connect external speakers.

Hmm, quite correct on the possible solution and the lack of static for an out-of-phase signal.

On the other hand, the speakers are fine, and as I said in the edit: the noise only appears about 2-3 seconds after the last sound has been played. The noise disappears once a sound plays, and then reappears again after it is finished playing. I can play an MP3 with no noise, but it returns once again 2-3 seconds after the MP3 finishes. This makes me believe now that the Pismo shuts off the outputs when no sound is being played to save energy (not surprising), and that in this state, some sort of shielding is not working correctly. This machine was pulled completely apart by someone before it entered my hands, so this is a possibility as well. This is running 9.2.2 (waiting for RAM to ship so I can boot back into 10.3) with an upgraded Hitachi 40GB HD I purchased for my Lombard awhile back.

I am just curious if my analysis of the problem is accurate.