The mysterious problems with my SE

[IIfx]

Well, the old thread became to hard to follow in my opinion, so I am making a new one with my current diagnosis. The system likes to hang at random times, and in general behaves very odd. If left idle for 5 minutes, the system will either be frozen or crash once you move the mouse or press a key. These crashes can be a simple lock-up or the screen going garbled, with the mac emitting a horrible screeching noise from the speaker. After the Mac has its seizure, it resets itself as if nothing even happened. I have removed the SCSI HD to eliminate problem sources. The Superdrive is fine, and reads disks without problems. Another odd thing is that there are 2 visible jumping vertical scanlines when one first turns on this SE. They go away after a short period of time.

I began my RAM testing, leaving the 2 factory samsung sticks in slot 1 and 2, and the mac boots to sad mac. (Code 0000000E 0000FFFF) I am assuming these are the bad sticks. EDIT: Only boots with all 4 slots populated. RAM Size jumper is set properly. There is a buzzing sound (faint) from the speaker when the mac is left idle, and it pulses when you do things.

Some other info: SE FDHD, mfd 1989, 4mb RAM. Tested with System 6.

 

[IIfx]

I just got this amazing bomb error box. It opened itself within itself many times making an interesting cascade effect. Then it locked up, and the speaker stopped buzzing. Wonderful.

 

[cjtmacclassic]

My Classic has the exact same problem, especially when the Moire screensaver is left running.

 

[IIfx]

My Classic has the exact same problem, especially when the Moire screensaver is left running.

Only mine is only booted from a System 6.0.8 install floppy. There should be no such problems I am really starting to think its capacitors. The macine is 21 years old after all. All the caps are nichicon caps too. I cant think of any other reason for this odd behavior.

 

[techknight]

you need a good multimeter, and preferably a scope to watch your 5V and 12V lines comming out of the power supply. Bet you have a voltage issue.

Ive seen SEs go into a reboot frenzy at random times, and all because of a faulty power supply.

 

[IIfx]

you need a good multimeter, and preferably a scope to watch your 5V and 12V lines comming out of the power supply. Bet you have a voltage issue.
Ive seen SEs go into a reboot frenzy at random times, and all because of a faulty power supply.

I did not think of that, I will check it when I can borrow a relatives multimeter.

 

[IIfx]

I checked all the lines coming off of the PSU. They start out at 12 or 5 and then drop to 0 rapidly.

The PSU is an Astec. Seems like every mac from the 80s with these Astecs have problems! (IIcx and IIci come to mind)

 

[IIfx]

After reassembling the mac, the SCSI HD decided to come to life. Progress I guess. Its slightly less unstable, and it still locks up hard if left alone for more than 5 minutes. When in active use its perfect.

I really dont understand what is causing this issue.

 

[techknight]

you could always put a logic analyzer on the CPU address/data bus and see what sgoing on when it locks up. or.. try another mainboard.

 

[IIfx]

you could always put a logic analyzer on the CPU address/data bus and see what sgoing on when it locks up. or.. try another mainboard.

If I could afford the equipment I would gladly do that but I am looking for cost-effective means of fixing this. Perhaps I should give up and sell this mac...

 

[IIfx]

I am looking at this more positively now.

The problem seems to be capacitors on the logic board or in the power supply. I am debating the path to take in the repair process to fix this. The logic board should be easy as all the capacitors are the same!

 

[techknight]

Yea you could have bad capacitors. they are at that age now.