I have a friend with a "dead" 9010a that acts just as yours does: Power-on gives the beep, but no display. It is easy to confirm if the display is good, as it has its own self-test modes, selectable by jumpers on the display's daugher-board (see the Service Manual section on the display for how to do that). As you say, the Service Manual doesn't cover the 3A firmware (and hardware -- no piggyback ROM board), which is annoying. Although I have a functional 9010a, until very recently (last month, in fact) I didn't have a z80 pod, so we couldn't perform most of the tests that the Service Manual describes, and my friend decided to just shotgun various ICs on the board (remove, test, and then socket a replacement chip), but that didn't find any problems. When we finally were able to use my 9010a/z80 setup to test my friend's unit, we quickly found that the 0-3FFF and 4000-7FFF ROMs were colliding, meaning that they both had the same contents and checksum, so we determined that the bank-select logic via the 82S123 PROM in U62 was faulty. Thanks to the kind assistance of a list-member, I got the image for U62, and was able to burn a new PROM. I have provided the PROM image-file and some diagnostic information to John who has uploaded it to the FTP site, so if you have that problem, you can fix it. Alas, this did NOT fix my friend's board, so like you we are suspecting the watchdog logic. We have yet to do another debugging session to (a) verify that the ROM bank-select logic is fixed and (b) follow the watchdog testing section. Hope that helps. grant.. On 2017-08-08 3:05 PM, robert via Techtoolslist wrote: my fluke 9010a rev 3a is not booting the diplay doesnt go on i think its a watch dog problem i have the service manual but it doesnt seem to cover the 3a rev fir mware for the rom signatures all my power test points are good and also i get a beep when power on but no display does anyone have any idea what could be the ca use of the shutdown _______________________________________________ Techtoolslist mailing list [1]Techtoolslist@flippers.com [2]https://pairlist7.pair.net/mailman/listinfo/techtoolslist FTP site is: [3]ftp://ttl.arcadetech.org/TTL/Test_Equipment Archive site: [4]http://seven.pairlist.net/pipermail/techtoolslist/ References 1. mailto:Techtoolslist@flippers.com 2. https://pairlist7.pair.net/mailman/listinfo/techtoolslist 3. ftp://ttl.arcadetech.org/TTL/Test_Equipment 4. http://seven.pairlist.net/pipermail/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/