mikerofone
Experienced Member
Hi all,
I've recently managed to get hold of an Apple Lisa 2 in pretty nice condition, including an external 5MB Profile in working condition. I have one issue with it though: The Lisa power supply emits some whine or buzz that seems to modulate based on load. Changing the screen brightness or contrast changes the frequency, as does system activity like starting programs. I've taken some videos that include the sound, and pictures of the PSU in this album: https://photos.app.goo.gl/j34Jd5DA2rBbWwR66
The seller said that all Lisa PSUs are noisy these days, which I can believe given that the age of the units these days. But I am concerned that this might be indicate of an upcoming, preventable failure. The seller is offering to swap the PSU for a different, quieter one, but I'd like to understand the problem better before stepping into action here.
Cheers
mikerofone
I've recently managed to get hold of an Apple Lisa 2 in pretty nice condition, including an external 5MB Profile in working condition. I have one issue with it though: The Lisa power supply emits some whine or buzz that seems to modulate based on load. Changing the screen brightness or contrast changes the frequency, as does system activity like starting programs. I've taken some videos that include the sound, and pictures of the PSU in this album: https://photos.app.goo.gl/j34Jd5DA2rBbWwR66
The seller said that all Lisa PSUs are noisy these days, which I can believe given that the age of the units these days. But I am concerned that this might be indicate of an upcoming, preventable failure. The seller is offering to swap the PSU for a different, quieter one, but I'd like to understand the problem better before stepping into action here.
- Could this be a side effect of aging caps? While the unit was offered as recapped, the capacitors on the PSU seem original (including cracked RIFAs).
- Since I cannot run the Lisa off the PSU without having it fully inserted in the case, I cannot exactly make out where the noise is coming from. Could it be the marked component in this picture (not mine, forgot to take a good picture when I had mine open)? Is that some sort of regulator?
- Do you think it's safe to operate the Lisa with that issue present? I see that the pixels on the screen are "dancing" slightly (visible in the video, scanlines are not in perfect horizontal alignment).
- It's a 120V 1.2Amp PSU running on a 230V->120V step-down converter (product link). Could that be creating line noise that the Lisa amplifies? (Converting the PSU to 230V would rule that out, but that might be a topic for a different thread. )
Cheers
mikerofone