Your logic probe will probably crash the clock when probing u9 p38/p39. Check p37 "E" instead, it is the clock output which you can safely test and trust the results.

Does your game have the data buffers still installed? If you have a data problem, you can sometime get some activity where as a address problem you are typically dead dead.

Then your clock is probably fine.

If you have a frequency counter, it is around 900k

It is time to check out every data line and every address line for shorts and opens. Easiest done with just the CPU installed.

Next check the CE for the roms and rams and so on.

Like I said above, the data buffers crap out most often.

Trust the diag built into the flipper roms over the leon memory test. It is much more reliable as long as the MPU boots up somewhat. Leon test can pass when the RAM is actually bad.

In fact... ditch the leon test chip. Andre's works much better if you are willing to build the test LED board that hooks up to a display connector.

Leon's test eprom is indeed not very accurate testing the memory chips. It inspired me to program my own test eprom for Williams system 3-6 and system 7. They are available for everyone who wants to try it.

Marco

Great stuff Marco! Do we just send you a PM and request it, or is it available to download somewhere?

Thanks There isn't a website yet. I am sorry about that. If you send me a PM with an emailaddress i will send the images and a description.

Marco