{"id":1078,"date":"2016-01-09T13:19:44","date_gmt":"2016-01-09T13:19:44","guid":{"rendered":"http:\/\/www.randomorbit.co.uk\/?p=1078"},"modified":"2016-01-09T13:19:44","modified_gmt":"2016-01-09T13:19:44","slug":"retrochallenge-2016-week-1-done-some-progress","status":"publish","type":"post","link":"https:\/\/www.randomorbit.co.uk\/?p=1078","title":{"rendered":"Retrochallenge 2016 \u2013 Week 1 done. Some progress."},"content":{"rendered":"

So here we are, one week in to RC2016-01 and what do we have to show for it?<\/p>\n

As you saw in my previous post<\/a>, I have taken the lid off the VT180 and it sits as a bare metal cage while I try to figure out what’s wrong.<\/p>\n

\"151231-IMG_20151231_174248\"<\/a>The initial display (shown on the left) has changed and is less verbose.\u00a0\"160106-IMG_20160106_194827\"<\/a> I’m not sure what happened to trigger the change.<\/p>\n

The screen display is no longer in sync and rolls very quickly.<\/p>\n

In order to help with the repair I have taken the VT100 board out of the card cage and I have it plugged in to the cable that was powering the card edge connector on the card cage. It’s clearly straight through so should be fine.<\/p>\n

\"160106-IMG_20160106_194705\"<\/a>That means that I can get to the board with my meter and ‘scope etc. I have also removed the AVO (advanced Video Output) board and the small inter-connect board. This hasn\u2019t changed the symptoms at all.<\/p>\n

The first real diagnostic work was to measure the voltages from the PSU. They all seem fine.<\/p>\n

I have been able to use a logic analyser (borrowed – I really want one of these) and I’ve been taking a look on the bus.<\/p>\n

have attached three screen shots taken of the logic analyser screens. I have 18 channels and so I have the data bus, the lower 8 bits of the address bus and the synch pin. All signals are from clips on the 8080.<\/p>\n

I have the triggers set to stable high on sync (start of new instruction) and 0 on the address bus. I put the analyser to wait for trigger and turned on the VT180.
\nThe three shots are from the same run and I’ve just stepped through the time a little to show what happens at start up.<\/p>\n

\"vt180-digiview-3\"<\/a>\"vt180-digiview-2\"<\/a>\"vt180-digiview-1\"<\/a>I get this with or without the keyboard. With the keyboard, all of the lights are lit. When I first started on this repair, a few, normal looking lights came on first and then, after a while, they all came on. It’s a funny old world.<\/p>\n

 <\/p>\n","protected":false},"excerpt":{"rendered":"

So here we are, one week in to RC2016-01 and what do we have to show for it? As you saw in my previous post, I have taken the lid off the VT180 and it sits as a bare metal cage while I try to figure out what’s wrong. The initial display (shown on the … Continue reading Retrochallenge 2016 \u2013 Week 1 done. Some progress.<\/span> →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_coblocks_attr":"","_coblocks_dimensions":"","_coblocks_responsive_height":"","_coblocks_accordion_ie_support":"","footnotes":""},"categories":[47,115,114,33,98,112],"tags":[],"class_list":["post-1078","post","type-post","status-publish","format-standard","hentry","category-c93-blog-posts","category-dec-vt-180","category-digital-equipment-corporation","category-c84-retro-tech","category-retrochallenge","category-retrochallenge-20161"],"featured_image_src":null,"author_info":{"display_name":"andy","author_link":"https:\/\/www.randomorbit.co.uk\/?author=1"},"_links":{"self":[{"href":"https:\/\/www.randomorbit.co.uk\/index.php?rest_route=\/wp\/v2\/posts\/1078","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.randomorbit.co.uk\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.randomorbit.co.uk\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.randomorbit.co.uk\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.randomorbit.co.uk\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1078"}],"version-history":[{"count":1,"href":"https:\/\/www.randomorbit.co.uk\/index.php?rest_route=\/wp\/v2\/posts\/1078\/revisions"}],"predecessor-version":[{"id":1079,"href":"https:\/\/www.randomorbit.co.uk\/index.php?rest_route=\/wp\/v2\/posts\/1078\/revisions\/1079"}],"wp:attachment":[{"href":"https:\/\/www.randomorbit.co.uk\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1078"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.randomorbit.co.uk\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1078"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.randomorbit.co.uk\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1078"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}