{"id":370,"date":"2022-05-27T14:02:46","date_gmt":"2022-05-27T14:02:46","guid":{"rendered":"http:\/\/darylwhite.net\/?p=370"},"modified":"2022-05-31T11:58:37","modified_gmt":"2022-05-31T11:58:37","slug":"topward-tps-4000-power-supply-repair","status":"publish","type":"post","link":"https:\/\/darylwhite.net\/index.php\/2022\/05\/27\/topward-tps-4000-power-supply-repair\/","title":{"rendered":"Topward TPS-4000 Power Supply Repair"},"content":{"rendered":"\n<p>The Topward TPS-4000 is a linear bench power supply with two independent adjustable outputs and a third fixed 5V output. It is this 5V output that has failed.<\/p>\n\n\n\n<p>Original schematic (incorrect)<\/p>\n\n\n\n<p>The original schematic seems to be missing the pass transistor and has the other transistors connected in an odd manner which suggested something might not be right.<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" src=\"https:\/\/pomf2.lain.la\/f\/rd8l71hj.jpg\" alt=\"\"\/><\/figure>\n\n\n\n<p>Reverse engineered schematic (correct)<\/p>\n\n\n\n<p>The transformer\/bridge rectifier\/filter capacitors have omitted for clarity.<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><a href=\"https:\/\/darylwhite.net\/wp-content\/uploads\/2022\/05\/PXL_20220527_134936617-scaled.jpg\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"706\" src=\"https:\/\/darylwhite.net\/wp-content\/uploads\/2022\/05\/PXL_20220527_134936617-1024x706.jpg\" alt=\"\" class=\"wp-image-387\" srcset=\"https:\/\/darylwhite.net\/wp-content\/uploads\/2022\/05\/PXL_20220527_134936617-1024x706.jpg 1024w, https:\/\/darylwhite.net\/wp-content\/uploads\/2022\/05\/PXL_20220527_134936617-300x207.jpg 300w, https:\/\/darylwhite.net\/wp-content\/uploads\/2022\/05\/PXL_20220527_134936617-768x529.jpg 768w, https:\/\/darylwhite.net\/wp-content\/uploads\/2022\/05\/PXL_20220527_134936617-1536x1059.jpg 1536w, https:\/\/darylwhite.net\/wp-content\/uploads\/2022\/05\/PXL_20220527_134936617-2048x1411.jpg 2048w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/a><\/figure>\n\n\n\n<p>LTspice Simulation<\/p>\n\n\n\n<p>Q2, BD912, would have originally been a 2SA699 transistor.<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><a href=\"https:\/\/darylwhite.net\/wp-content\/uploads\/2022\/05\/tps_spice.png\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"458\" src=\"https:\/\/darylwhite.net\/wp-content\/uploads\/2022\/05\/tps_spice-1024x458.png\" alt=\"\" class=\"wp-image-386\" srcset=\"https:\/\/darylwhite.net\/wp-content\/uploads\/2022\/05\/tps_spice-1024x458.png 1024w, https:\/\/darylwhite.net\/wp-content\/uploads\/2022\/05\/tps_spice-300x134.png 300w, https:\/\/darylwhite.net\/wp-content\/uploads\/2022\/05\/tps_spice-768x343.png 768w, https:\/\/darylwhite.net\/wp-content\/uploads\/2022\/05\/tps_spice.png 1384w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/a><\/figure>\n\n\n\n<p>Failed components &#8211; Motorola MJ2955 pass transistor and 2SA1015 sense transistor.<\/p>\n\n\n\n<p>The MJ2955 has a short circuit between the collector &amp; emitter and the 2SA1015 has some odd junction behavior when tested under forward &amp; reverse bias.<\/p>\n\n\n\n<p>I&#8217;m waiting for a replacement MJ2955 and the 2SA1015 will be replaced with whatever jellybean transistor I have at hand.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>The Topward TPS-4000 is a linear bench power supply with two independent adjustable outputs and a third fixed 5V output. It is this 5V output that has failed. Original schematic (incorrect) The original schematic seems to be missing the pass transistor and has the other transistors connected in an odd manner which suggested something might [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[14],"tags":[],"class_list":["post-370","post","type-post","status-publish","format-standard","hentry","category-topward-tps-4000"],"_links":{"self":[{"href":"https:\/\/darylwhite.net\/index.php\/wp-json\/wp\/v2\/posts\/370","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/darylwhite.net\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/darylwhite.net\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/darylwhite.net\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/darylwhite.net\/index.php\/wp-json\/wp\/v2\/comments?post=370"}],"version-history":[{"count":3,"href":"https:\/\/darylwhite.net\/index.php\/wp-json\/wp\/v2\/posts\/370\/revisions"}],"predecessor-version":[{"id":388,"href":"https:\/\/darylwhite.net\/index.php\/wp-json\/wp\/v2\/posts\/370\/revisions\/388"}],"wp:attachment":[{"href":"https:\/\/darylwhite.net\/index.php\/wp-json\/wp\/v2\/media?parent=370"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/darylwhite.net\/index.php\/wp-json\/wp\/v2\/categories?post=370"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/darylwhite.net\/index.php\/wp-json\/wp\/v2\/tags?post=370"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}