MacIntosh Plus strange startup behavior

[fit2page]

Hi,

Got some strange startup behavior on one of my Plus machines. I can start it but on the first screen there is video garble, the moment the second screen appears (with the floppy question) the video is OK. I already swapped boards and it is a logic board issue. Can this be some kind of screen buffering thing? Thanks in advance for any input/pointers!

Marc

 

[bibilit]

A stuck reset line ?

 

[arroz]

Hi!

The Plus (and many others like the PowerBook 145) always boot with video garbage on the screen for a second or two. You usually can’t see it because the CRT takes time to warm up, but on a PowerBook it’s visible since the LCD fires up immediately. I noticed that on the Plus as well while developing my MacDVI adapter and also when using RGBtoHDMI.

It shows garbage for about a second, then clears the screen and shows the diagonal pattern while the RAM is being tested (may take quite a while if you have 4MB, and the screen flashes black occasionally) and finally switches to the checkerboard pattern with the question mark floppy disk.

Regadds

Miguel Arroz

 

[fit2page]

Hi Miguel! Thanks for your reaction, this behavior is new to me, never experienced it before on a Plus. But OK we have to live with that then. Another problem on this machine is that there is no sound...a while I had a kggggg instead of the start chime but now the sound is completely dead. Speaker is tested and OK, I can hear the click on start-up. When I listen very carefully tyhere is a 1Hz ticking sound coming from the audio line. I also tested all traces/connections round the SND chip, everything OK there. Is this a known issue to you?