Ok so I got one of my SI boards working. And that let me figure out what was going on here. The pod (twisted pair cable) would always show this error when doing bus test and ram reads / writes were flakey. Any of my 3 boards. I have 3 of the 8080 pods (two flat cable and this one twisted pair). But the flat cable pods have never been able to work reliably with the midway 8080 boards for me. Read 2000 loop would toggle values. Obvious the address drivers were having trouble. So I did some substitutions between pods. Swapped the twisted pair cable over to one of the flat cable pods and WONDER of WONDERS. The pod now will do a RUN UUT, and everything is golden, read / writes are fine now. (Same board that is giving the A13 error). So I swapped the CPU boards (and noticed something odd, the twisted pair pod has a different rom part number than the two flat cable pods). No change, still A13. OK so must be in the IO board. Looked at the schematic and found A13 goes through the protection chip (praying that is not bad). And from there to a 245. Well those go bad, and there is another one on the board so I swapped them. No more A13 error. And looking at the schematic that buffer gate isn't used in the other location so it is "Fixed" for now. Will look at getting some replacements for these in (not standard LS family). I tried the flat cables with the clock resistors jumped and it didn't make any difference. The twisted pair doesn't need them jumped. At the end of the day all 3 pods work with the twisted pair cable. But ONLY with that cable. So where do I get new twisted pair cables for these? Anyone? David -----Original Message----- From: Techtoolslist [mailto:techtoolslist-bounces@flippers.com] On Behalf Of John Robertson Sent: Wednesday, July 10, 2019 6:41 AM To: techtoolslist@flippers.com Subject: Re: [Techtoolslist] Fluke 9010 bus test address tied message confusion On 2019/07/10 12:10 a.m., David Shoemaker wrote:
Working on a space invaders board.
8080 pod, passes self-test.
Put it onto UUT and hit auto. Getting an error that does make sense.
ADDR bits 13 tied-Loop?
Thought at first that was bits 1 & 3 tied. But probing around didn't find anything. So I tried tying them together myself to see what happens.
ADDR Bits 1 and 3 tied - loop?
Uh, ok so they are explicit on the two bits tied. That's good to know. But why is it only telling me one bit?
So I pulled out the manual and from the bus test error messages table there should never be a "bits" message without two bits. But I am only getting one (and no MORE led, and more button does nothing).
The only single bit error should be if bit tied low or high. But that is not the message (and it says "bit" not "bits").
I tried exercising bit 13, did a write @ 2000 = 0, probe set on address and can see the line being driven high. And no other bits are being driven when I check.
Thoughts?
Thanks,
David
When I get these errors (not specific about what it is tied too) I search the entire line and usually find it is shorted to something the CPU has no connection to. For example on the SI board - do you have the sub-board unplugged? Take a look in the socket for junk/bent pin shorting A13 to some other line (if A13 goes to that socket). This error simply means that the Fluke can't exercise A13 easily and it assumes it is stuck to some other line that the pod can't 'see'. Have you done a Diode Test to compare A13/Vcc/GND results with A12 or A14? They should be the same with the Fluke pod disconnected. John :-#)# -- How to subscribe or unsubscribe from TTL http://seven.pairlist.net/mailman/listinfo/techtoolslist _______________________________________________ Techtoolslist mailing list Techtoolslist@flippers.com https://pairlist7.pair.net/mailman/listinfo/techtoolslist FTP site is: ftp://ttl.arcadetech.org/TTL/Test_Equipment Archive site: http://seven.pairlist.net/pipermail/techtoolslist/