[Techtoolslist] Logic Analyzers and pulling out what little hair I have left...

[John Robertson]

Well, not that I need one very often - the Fluke 9010A finds 99% of the 
problems - but right now I have a headache with a Williams F-14 pinball 
MPU that refuses to produce speech. According to the 9010A everything 
seems just fine, I can access the PIA, ROM signatures are correct (paged 
ROM, but pages seem to work correctly). There really is very little 
hardware - two Eproms, a 6802, 2106 RAM, some logic glue, and a 6821 
PIA, but it won't run the speech data.

Using my audio probe I don't even get the sounds on D0 so I know the 
problem is actually before the 6821. Audio probes are fun to use for 
troubleshooting digital audio as you can even hear the sounds on the 
logic data bus - weak and fuzzy, but clearly the sounds you are looking for.

So, I figure I'd dig up one of my ancient logic analyzers that I bought 
around 2002 figuring I'd use them some day. Two Arium ML4100s (one 
deader) and an Arium ML4400. However, can I find them? No. We moved the 
shop after 35 years last May and my helpful staff buried two of the 
three Ariums somewhere in the 6,000 sq ft shop...the only one I could 
find was a dead ML4100.

So, now I figure I'd see what was online for modern LAs and there are 
some interesting 16 bit units including a few from China that should 
work on the SIGROK software.

http://www.qdkingst.com/en

The point of this ramble? A question - anyone here using one of these 
modern inexpensive LAs (or another brand) and cares to tell us your 
experiences?

I guess the other point is, has anyone troubleshot a Williams 
sound/speech section and can tell me what I have overlooked? I do know 
(substitution) that RAM/ROM/CPU/PIAs are all good, have replaced the 
glue chips, but really, they changed state correctly for the Fluke as 
well as my logic comparator. There is some corrosion on the board, but 
suspect sockets replaced and while I did have a short from R/W to 
another line, I did track that down and fix it. All sounds EXCEPT speech 
work just fine. Gah! Frigging FM.

Thanks,

John :-#)#

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