superjer2000
Well-known member
I finished restoring a Mac Classic (recapping logic and analog boards and fully cleaning the unit) and when booting it up for the first time I was presented with a non-functioning clock (the seconds didn't count up in the control panel). I've had this issue before but it was a broken trace between the oscillator and the RTC chip which was easily repaired.
On this machine, all of the traces on the Bomarc schematics from the clock chip test ok.
I grabbed my oscilloscope and tested the oscillator (Y1) and I got a good clock signal. The weird thing is, once I touched a probe to (I think) either pin of the oscillator, the clock started working (seconds started counting) and seemed to stay working until I shutdown. I only left it on for a couple of minutes in between tests so I'm not sure if it would have stopped eventually. This was repeatable over multiple attempts.
I soldered some jumper wires from the RTC to Y1 and from Y1 to its capacitors on the back side of the board with no change (except on one boot the clock did work but after shutting down it wouldn't again unless I touched an oscilloscope probe to a leg of Y1.
I plan to remove the RTC chip to see where all of the traces go (I would think there are more than what Bomarc shows given it's a 20 pin IC and I might try replacing the crystal. I wanted to see if anybody here had seen something like this before or might have an idea why jumpstarting Y1 seems to work and what that indicates about the problem.
On this machine, all of the traces on the Bomarc schematics from the clock chip test ok.
I grabbed my oscilloscope and tested the oscillator (Y1) and I got a good clock signal. The weird thing is, once I touched a probe to (I think) either pin of the oscillator, the clock started working (seconds started counting) and seemed to stay working until I shutdown. I only left it on for a couple of minutes in between tests so I'm not sure if it would have stopped eventually. This was repeatable over multiple attempts.
I soldered some jumper wires from the RTC to Y1 and from Y1 to its capacitors on the back side of the board with no change (except on one boot the clock did work but after shutting down it wouldn't again unless I touched an oscilloscope probe to a leg of Y1.
I plan to remove the RTC chip to see where all of the traces go (I would think there are more than what Bomarc shows given it's a 20 pin IC and I might try replacing the crystal. I wanted to see if anybody here had seen something like this before or might have an idea why jumpstarting Y1 seems to work and what that indicates about the problem.
