Mac 128k Sad mac at startup

[Moofo]

I tried. In fact I tried the logic board with no floppy drive...

I thought about this as well, since it looks pretty shoddy to me.

I will just wait until I go to my hometown to fetch a 512 or a Plus to test the logic board.

I will try in the next few weeks to Image all the floppies I have here. I have lots of Apple Service Floppies. They might be useful for the folks here.

I also have lots of Old Apple Service manuals Paperbacks I might just scan for the community...

 

[Mac128]

Did your artifacts look like this by any chance?

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=290161899510

Also, have you checked voltages on your floppy port? That would also indicate if you have an analogue board problem.

 

[Moofo]

No check on voltages...

The artifacts look like this...

 

[Moofo]

I tried a Mac 512 Logic board and the machine boots...

SO the problem is really with the Logic board...

 

[tomlee59]

Not so fast. If the supply voltage is marginal, then some logic boards may work, and others may not. The only way to preclude power supply problems is to make an actual measurement.

Also, if you put the 128K board back in, does the problem recur? Many power supply problems turn out to be connector problems, which the simple act of disconnecting and reconnecting can fix (temporarily, at least).

That said, you probably do have a logic board problem (bad RAM is more and more likely to be the correct diagnosis, given what you've found, and given the quality of US DRAM at that time). But check the other possibilities first.