Blown RAM card?

[AltairClone]

Try an 8.2K if you have one. If not, see if you have a 7.5K

[Ttpilot]

Try an 8.2K if you have one. If not, see if you have a 7.5K

Okay, I swapped an 8.2k in for R41. Here's the result:

Phi1 + phi2

Also the measurements

Phi1:

Phi1 measurements

Phi2:

Phi2 measurements

Maybe phi2 is a bit long, too?

[AltairClone]

Ok, that looks great on phi1 and got us up to the minimum phi2 to phi1 timing. Now let’s shorten phi2 a bit to get some headroom. I’d use a 5.6K for R42. That should get phi2 down to just below 250ns and gain us about 30ns of headroom.

Mike

[Ttpilot]

Now let’s shorten phi2 a bit to get some headroom

With 5.6K in R42

Phi1 + phi2 (R41 = 8.2K ohms, R42 = 5.6k ohms)

[AltairClone]

That looks perfect. All pulse widths and the phi1 and phi2 clock edges relative to each other are well within spec. Any problems you have with the computer are now not related to processor clock issues.

Mike

[Ttpilot]

That looks perfect. All pulse widths and the phi1 and phi2 clock edges relative to each other are well within spec. Any problems you have with the computer are now not related to processor clock issues.

Mike

Thanks very much for the help. It's been a fun learning experience.

When I power on the status lights and wait light are all correct. But I seem to have a stuck address line and data line, and a reset takes me back to address 02 instead of 00. I guess I need to take the front panel all apart and inspect everything on that. Sigh. At least I'm closer!

[AltairClone]

Before you take apart the front panel, I’d remove and reseat the data connector from front panel to the CPU board a few times. Also look at the wires and female pins of that connector closely and make sure none of those wires are broken where they solder at the front panel.

Mike