{"id":66,"date":"2022-02-27T13:51:31","date_gmt":"2022-02-27T13:51:31","guid":{"rendered":"https:\/?p=66"},"modified":"2025-11-26T08:28:21","modified_gmt":"2025-11-26T08:28:21","slug":"minipet-debug","status":"publish","type":"post","link":"https:\/\/timsretrocorner.com\/?p=66","title":{"rendered":"MiniPET Debug"},"content":{"rendered":"\n<figure class=\"wp-block-embed is-type-video is-provider-youtube wp-block-embed-youtube wp-embed-aspect-16-9 wp-has-aspect-ratio\"><div class=\"wp-block-embed__wrapper\">\n<iframe loading=\"lazy\" title=\"MiniPET DEBUG (Make part 3)\" width=\"800\" height=\"450\" src=\"https:\/\/www.youtube.com\/embed\/6gNZUSXprD8?feature=oembed\" frameborder=\"0\" allow=\"accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture\" allowfullscreen><\/iframe>\n<\/div><\/figure>\n\n\n\n<p>The <a href=\"https:\/\/www.thefuturewas8bit.com\/shop\/tynemouth-products\/minipet4080.html\">MiniPET 40\/80<\/a> is built, we plug it in, and . . . . nothing. It doesn&#8217;t work. There&#8217;s a short on the board in the worst possible way &#8211;  directly between +5 volts and ground. We have to debug it if we don&#8217;t want it just to be an expensive paperweight.<\/p>\n\n\n\n<p>So where do we start? There are no schematics for this board, the PCP is smothered in white paint so we can&#8217;t se the traces even. This means we have to go back to first principles. Start with the most likely and work towards the less likely.<\/p>\n\n\n\n<p>Is it a faulty chip? Well I&#8217;ve removed all the ICs and it&#8217;s still shorted, so it&#8217;s not that.<\/p>\n\n\n\n<p>Is something in backwards?<\/p>\n\n\n\n<p>Is there a solder bridge between adjacent connections? Well this is the most likely, but a visual inspection with a magnifying lens doesn&#8217;t show anything. So maybe it&#8217;s lurking underneath a chip socket?<\/p>\n\n\n\n\n\n<p><\/p>\n\n\n\n<p>Well, I&#8217;m not going to spoil the fun by telling you what the problem was (yes I did fix it!) &#8211; you&#8217;ll have to watch the video for that. But I will say &#8212; with the advantage of 20-20 hindsight &#8212; that checking for shorts early in the build process, and ideally after each section, will prevent the need for drastic remedial action at the end of the project. If you&#8217;re thinking of tackling this project yourself (or any other similar project), it&#8217;s something to bear in mind.<\/p>\n\n\n\n<p>The MiniPET does have some built-in diagnostics: there are two self-test modes that can be set through the DIP switches. Of course it does have to be working enough to get a display and run those tests. But once it does, it&#8217;s nice to see them all pass.<\/p>\n\n\n\n<figure class=\"wp-block-image size-large is-style-default\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"576\" src=\"https:\/\/timsretrocorner.com\/wp-content\/uploads\/2022\/02\/PetTest-1024x576.png\" alt=\"Self-test display\" class=\"wp-image-68\" srcset=\"https:\/\/timsretrocorner.com\/wp-content\/uploads\/2022\/02\/PetTest-1024x576.png 1024w, https:\/\/timsretrocorner.com\/wp-content\/uploads\/2022\/02\/PetTest-300x169.png 300w, https:\/\/timsretrocorner.com\/wp-content\/uploads\/2022\/02\/PetTest-768x432.png 768w, https:\/\/timsretrocorner.com\/wp-content\/uploads\/2022\/02\/PetTest-1536x864.png 1536w, https:\/\/timsretrocorner.com\/wp-content\/uploads\/2022\/02\/PetTest.png 1920w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption>Passed!<\/figcaption><\/figure>\n\n\n\n<p>With that done, we can start to use it: run demos, play games, write software&#8230;.<\/p>\n\n\n\n<p>Oh, and yes I do know the &#8216;Z&#8217; key is upside down \ud83d\ude09<\/p>\n","protected":false},"excerpt":{"rendered":"<p>The MiniPET 40\/80 is built, we plug it in, and . . . . nothing. It doesn&#8217;t work. There&#8217;s a short on the board in [&#8230;]<\/p>\n","protected":false},"author":1,"featured_media":67,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[9,8],"tags":[],"class_list":["post-66","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-commodore","category-pet-cbm"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v26.4 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>MiniPET Debug - Tim&#039;s Retro Corner<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/timsretrocorner.com\/?p=66\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"MiniPET Debug - Tim&#039;s Retro Corner\" \/>\n<meta property=\"og:description\" content=\"The MiniPET 40\/80 is built, we plug it in, and . . . . nothing. 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