Dead Plus

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JDW's picture
Joined: Mar 18 2006
Posts: 160

I have an associate with a dead Plus. No video and a strange "rattling sound" when turned on. (Attached is the rattling sound. I could only upload it to AppleFritter by chaning the extention to "jpg." But this will prevent you from hearing the sound. So please download the file via CONTROL-CLICK and then change the "jpg" part to "mp4" or it won't play in OS X.)

To continue the list of problems...

No bad smells. No burn marks on analog board upon examination. Putting the logic board from that bad Plus into a known-good Plus doesn't boot the known-good Plus (i.e., logic board bad). But putting a known good logic board into the bad Plus doesn't fix the bad Plus either (i.e., analog board bad). Voltage levels as taken at the floppy drive connector are as follows:

+1.3V (instead of normal +5V)
+7.5V (instead of normal +12V)
-7.5V (instead of normal -7.5V)

Thoughts and insights would be appreciated.

Thank you.

Plus_rattling.jpg171.6 KB

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pmjett's picture
Joined: Sep 5 2005
Posts: 181
How about unloaded?

What's the power supply doing when it is unloaded? Do you still have out of spec voltages? Does the filament in the CRT light? (not sure how it could with voltages so far out of whack.)

BTW, that rattling is nuts... I can't even imagine what in a Plus could do that.


how's your se/30?


128K, 512K, Mac Plus, Classic, SE/30, Indigo iMac, B&W, Sawtooth, iBook G4, Mini. Numerous SGI and Sun boxen.

protocol6v's picture
Joined: Apr 22 2006
Posts: 339
Sounds like the floppy drive

Sounds like the floppy drive jammed on something. Or, does the plus have a fan like the SE?


MacBook Pro, 2.2GHz SR Core 2 Duo, 120GB HD, 2GB RAM,
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JDW's picture
Joined: Mar 18 2006
Posts: 160
Not a drive or fan

I confirmed it is not the drive because the sound occurs when all drive were yanked out. It's not a fan because there is no fan.

Will have to test what happens with the analog board connected but all loads (logic board, CRT, etc.) removed.


astro_rob's picture
Joined: Mar 19 2005
Posts: 320
Damaged CRT?

I had a damaged VGA monitor some time back that made a similar sound, though a bit slower in cadence. I have a dead Plus here, CRT works fine, only problem is the analog board. JDW, where are you located?


Tinker Ergo Sum!
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JDW's picture
Joined: Mar 18 2006
Posts: 160
Located in Japan, but my asso

Located in Japan, but my associate with the Plus is located in the states.

More info:

(1) When the main cable from the analog board to the motherboard is disconnected, it makes the rattling sound for only a half second and then immediately the rattling sound goes away and the machine makes the expected "crow-bar flupping sound." So except for that initial half second rattling sound, the crowbar circuit seems to be working.

(2) When I the logic board from the bad Plus is placed into the good Plus, the screen shows up for 5-7 seconds with garbage artifacts on it, as if the bits were scrambled. After this, single pixel thin horizontal white lines that only show up for a second. They show up one
little line at a time, and move down the screen when they reappear, and that's
all it will do. Horizontal lines are often a sign of a bad analog board, but again, in this test the bad LOGIC BOARD was placed in a good Plus with a good analog board. Pina's Dead Mac Scrolls mentions the possibility of a bad LAG PAL on the logic board in the case of lines, but the book makes no mention of the scrambled pixels.