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I’m wondering if it was a trim pot as opposed to a capacitor? Based on the trace cut, the trim pot may have been in series with the crystal drive circuit to not over-drive the xtal.

Have you looked at phi1 and phi2 to make sure the CPU is getting a good clock?

Mike

AltairClone wrote:I’m wondering if it was a trim pot as opposed to a capacitor? Based on the trace cut, the trim pot may have been in series with the crystal drive circuit to not over-drive the xtal.

Have you looked at phi1 and phi2 to make sure the CPU is getting a good clock?

Mike

I can't check those yet, I'm waiting for my oscilloscope to arrive. Good news is, it should be here any day.

Now that I've got the scope I tried to look at phi1 and phi2 of the 8800b clock. I think I checked the correct IC and pins. The 8800b manual states IC-F which is an 8224. Looking at the spec sheet, pins 10 and 11 are phi2 and phi1.

The clock is obviously running and the timing looks fine - which is expected with an 8224 clock chip.

Mike