512K CRT not working until the analog board warms up

Breezy

New Tinkerer
Nov 4, 2021
9
13
3
51
North Carolina, USA
Recently I was able to acquire a 512K compact mac. When initially powered on the system bongs and boots from the floppy, but the crt remains blank. If you wait long enough to allow the analog board to get sufficiently warm, the crt will begin working. As the temperature rises the crt will blink until it achieves a steady state. From a cold start, this process could take up to 10 minutes. Any suggestion on what to troubleshoot first?
 

pfuentes69

Active Tinkerer
Oct 27, 2021
380
293
63
Switzerland
Sounds like cracked solder joints on the analog board -- a common problem with that model. As the machine heats up, the components expand slightly and eventually make connection.
Yep... that could be indeed the cause too... a way to confirm is tapping the left side of the Mac, and see if that makes it work.
 

Breezy

New Tinkerer
Nov 4, 2021
9
13
3
51
North Carolina, USA
Sounds like cracked solder joints on the analog board -- a common problem with that model. As the machine heats up, the components expand slightly and eventually make connection.
Colin,
You were correct. I reflowed all the connectors and the fly back and my problem was solved. See the attached picture. Thanks for pointing me in the right direction.
IMG_0375.jpeg
Brian