{"id":20373,"date":"2026-10-30T10:10:25","date_gmt":"2026-10-30T02:10:25","guid":{"rendered":"https:\/\/www.wehopower.com\/news\/q120b-four-rail-harness-verification\/"},"modified":"2026-10-30T10:10:25","modified_gmt":"2026-10-30T02:10:25","slug":"q120b-four-rail-harness-verification","status":"publish","type":"news","link":"https:\/\/www.wehopower.com\/fa\/news\/q120b-four-rail-harness-verification\/","title":{"rendered":"Q-120B Four-Rail Harness Verification: Prevent Voltage and Polarity Mix-Ups"},"content":{"rendered":"<div class=\"weho-blog-content\">\n<p><strong>Release a Q-120B service harness only when the voltage assignment, connector orientation and wrong-mate prevention agree.<\/strong> The B variant has +5 V, +12 V, \u22125 V and \u221212 V outputs. A wire list alone does not show whether a replacement harness can be reversed, inserted into a nearby socket or supplied under the wrong part number.<\/p>\n<p>This guide is for an OEM building a serviceable instrument with four supply rails. Its output is a harness verification record linking the exact supply variant to the receiver&#8217;s approved pins. It does not establish the receiver&#8217;s load compatibility or the supply&#8217;s performance under uneven loading; those remain separate design checks.<\/p>\n<nav class=\"toc\" aria-label=\"Article contents\">\n<p>In this article<\/p>\n<ol>\n<li><a href=\"#freeze-electrical-identity\">Start with the B variant and signed rail names<\/a><\/li>\n<li><a href=\"#freeze-connector-views\">Make the connector view impossible to misread<\/a><\/li>\n<li><a href=\"#wrong-mate-review\">Review the unwanted connection, not only the correct one<\/a><\/li>\n<li><a href=\"#separate-two-verifications\">Perform continuity and signed-voltage checks in separate stages<\/a><\/li>\n<li><a href=\"#service-release\">Keep the approved service kit aligned with production<\/a><\/li>\n<\/ol>\n<\/nav>\n<section id=\"freeze-electrical-identity\">\n<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_86 counter-hierarchy ez-toc-counter ez-toc-grey ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">\u0641\u0647\u0631\u0633\u062a \u0645\u0637\u0627\u0644\u0628<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"\u062a\u063a\u06cc\u06cc\u0631 \u0648\u0636\u0639\u06cc\u062a \u0641\u0647\u0631\u0633\u062a \u0645\u0637\u0627\u0644\u0628\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">\u062a\u063a\u06cc\u06cc\u0631 \u0648\u0636\u0639\u06cc\u062a \u062f\u0647\u06cc\u062f<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewbox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewbox=\"0 0 24 24\" version=\"1.2\" baseprofile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/www.wehopower.com\/fa\/news\/q120b-four-rail-harness-verification\/#Start_with_the_B_variant_and_signed_rail_names\" >Start with the B variant and signed rail names<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/www.wehopower.com\/fa\/news\/q120b-four-rail-harness-verification\/#Make_the_connector_view_impossible_to_misread\" >Make the connector view impossible to misread<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/www.wehopower.com\/fa\/news\/q120b-four-rail-harness-verification\/#Review_the_unwanted_connection_not_only_the_correct_one\" >Review the unwanted connection, not only the correct one<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/www.wehopower.com\/fa\/news\/q120b-four-rail-harness-verification\/#Perform_continuity_and_signed-voltage_checks_in_separate_stages\" >Perform continuity and signed-voltage checks in separate stages<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/www.wehopower.com\/fa\/news\/q120b-four-rail-harness-verification\/#Keep_the_approved_service_kit_aligned_with_production\" >Keep the approved service kit aligned with production<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/www.wehopower.com\/fa\/news\/q120b-four-rail-harness-verification\/#Use_the_project_record\" >Use the project record<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/www.wehopower.com\/fa\/news\/q120b-four-rail-harness-verification\/#Sources_and_further_reading\" >Sources and further reading<\/a><\/li><\/ul><\/nav><\/div>\n<h2><span class=\"ez-toc-section\" id=\"Start_with_the_B_variant_and_signed_rail_names\"><\/span>Start with the B variant and signed rail names<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>\u0631\u0627 <a href=\"https:\/\/www.wehopower.com\/fa\/product\/ce-approved-120w-quad-output-switching-power-supply\/\">WEHO Q-120 product table<\/a> identifies the Q-120B combination as +5 V, +12 V, \u22125 V and \u221212 V. The <a href=\"https:\/\/www.wehopower.com\/wp-content\/uploads\/2021\/11\/Q-120.pdf\">official Q-120 specification sheet<\/a> also distinguishes B from the +15 V\/\u221215 V C variant. Some family photographs show a different output combination. Use the exact model table and the received unit&#8217;s approved marking, not the appearance of a shared enclosure.<\/p>\n<p>Create the electrical interface record before assigning connector cavities. Give each conductor a rail name, its reference and a destination. A \u201c12 V\u201d annotation without a sign is inadequate where both +12 V and \u221212 V exist. Likewise, a voltage measured between two non-COM rails is not the same as either rail&#8217;s voltage relative to COM.<\/p>\n<div class=\"table-scroll\">\n<div class=\"table-wrap\" role=\"region\" aria-label=\"Data table\" tabindex=\"0\">\n<table>\n<thead>\n<tr>\n<th scope=\"col\">Circuit identity<\/th>\n<th scope=\"col\">Required record<\/th>\n<th scope=\"col\">Do not infer<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>+5 V, +12 V, \u22125 V, \u221212 V<\/td>\n<td>Signed nominal voltage; approved receiver range; reference.<\/td>\n<td>That two opposite signs can be exchanged.<\/td>\n<\/tr>\n<tr>\n<td>COM<\/td>\n<td>Specific intended return path and receiver reference.<\/td>\n<td>That COM and protective earth are interchangeable.<\/td>\n<\/tr>\n<tr>\n<td>Supply and receiver interface<\/td>\n<td>Exact drawing revisions and actual terminal markings.<\/td>\n<td>A terminal order from another Q-family photograph.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/div>\n<\/section>\n<section id=\"freeze-connector-views\">\n<h2><span class=\"ez-toc-section\" id=\"Make_the_connector_view_impossible_to_misread\"><\/span>Make the connector view impossible to misread<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>For every plug and receptacle, identify the connector manufacturer&#8217;s part number, cavity numbers, key or polarization option, contact type and the view used in the drawing. State \u201cmating face\u201d or \u201cwire-entry face,\u201d with a fixed datum such as the latch at the top. A mirrored view can produce an internally consistent harness drawing that is wrong at the receiver.<\/p>\n<p>Use wire identifiers that remain legible after assembly. Color can help technicians find a conductor, but the controlled cavity and circuit records must survive a color substitution. Include any splices, shared returns and unused cavities in the drawing so that an unrecorded change cannot hide inside a bundle.<\/p>\n<p>Check contact and wire suitability separately. Mechanical fit does not establish current rating, temperature performance, crimp acceptance or mating-cycle capability. Those must come from the selected connector system and its application specification, not from the Q-120B output table.<\/p>\n<\/section>\n<section id=\"wrong-mate-review\">\n<h2><span class=\"ez-toc-section\" id=\"Review_the_unwanted_connection_not_only_the_correct_one\"><\/span>Review the unwanted connection, not only the correct one<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p><a href=\"https:\/\/supplychain.molex.com\/content\/molex\/molex-dot-com\/language-masters\/en\/trends-insights\/engineering-insights\/connector-mating.html\" target=\"_blank\" rel=\"noopener\">Molex&#8217;s connector mating guidance<\/a> distinguishes polarization, which controls orientation within a pair, from keying, which separates similar interfaces. Visual coding can identify a function without physically preventing an incorrect connection. Apply that distinction to the actual service task: two differently colored plugs may still fit the same socket.<\/p>\n<figure class=\"figure\" id=\"figure-diagram\"><picture><source media=\"(max-width: 600px)\" srcset=\"https:\/\/www.wehopower.com\/wp-content\/uploads\/2026\/10\/decision-map-mobile-2.svg\" width=\"480\" height=\"1290\" type=\"image\/svg+xml\"><img loading=\"lazy\" src=\"https:\/\/www.wehopower.com\/wp-content\/uploads\/2026\/10\/decision-map-2.svg\" alt=\"Q-120B Four-Rail Harness Verification: Prevent Voltage and Polarity Mix-Ups  title=\" width=\"1200\" height=\"740\" decoding=\"async\" q-120b four-rail harness verification: prevent voltage and polarity mix-ups title =\"\"><\/picture><figcaption>Q-120B: prove the intended mate. Explanatory decision aid. Numerical examples are hypothetical, not measured product performance or an installation drawing. <a class=\"original-link\" href=\"https:\/\/www.wehopower.com\/wp-content\/uploads\/2026\/10\/decision-map-2.svg\">View original image<\/a><\/figcaption><\/figure>\n<p>The matrix below is a hypothetical review example, not a proposed Q-120B connector pinout. Each unwanted pairing needs a physical or procedural disposition before the harness is released. Inspect actual parts without power and without forcing an incompatible connector.<\/p>\n<div class=\"table-scroll\">\n<div class=\"table-wrap\" role=\"region\" aria-label=\"Data table\" tabindex=\"0\">\n<table>\n<thead>\n<tr>\n<th scope=\"col\">Attempted pairing<\/th>\n<th scope=\"col\">Required disposition in the example<\/th>\n<th scope=\"col\">Evidence recorded<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Four-rail harness \u2192 intended receiver<\/td>\n<td>Fits in the documented orientation.<\/td>\n<td>Correct part numbers, cavity map and latch engagement.<\/td>\n<\/tr>\n<tr>\n<td>Four-rail harness \u2192 adjacent auxiliary socket<\/td>\n<td>Mechanically blocked, or redesign required.<\/td>\n<td>Actual keying comparison and unpowered inspection.<\/td>\n<\/tr>\n<tr>\n<td>Four-rail harness \u2192 intended receiver reversed<\/td>\n<td>Blocked by the selected polarization.<\/td>\n<td>Drawing view and physical orientation check.<\/td>\n<\/tr>\n<tr>\n<td>Unapproved replacement harness \u2192 receiver<\/td>\n<td>Held outside the approved service kit.<\/td>\n<td>Controlled service part and substitution review.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/div>\n<p>A label alone may be a necessary instruction, but do not record it as a mechanical barrier. If a plausible incorrect mate remains possible, change the interface or document an engineering decision with the equipment&#8217;s risk assessment. This article does not claim a universal connector solution for every instrument.<\/p>\n<\/section>\n<section id=\"separate-two-verifications\">\n<h2><span class=\"ez-toc-section\" id=\"Perform_continuity_and_signed-voltage_checks_in_separate_stages\"><\/span>Perform continuity and signed-voltage checks in separate stages<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>First verify the isolated, unpowered harness against its controlled cavity map. Record intended continuity and unwanted shorts using a method suitable for the cable and disconnected equipment. Keep the receiver isolated where required; do not apply a cable test voltage to electronic inputs without their manufacturer&#8217;s approval.<\/p>\n<p>Then use the equipment&#8217;s approved commissioning procedure to verify signed voltages at the receiving interface before exposing the receiver to an unverified harness. A qualified person must control access to the supply&#8217;s AC terminals. Use the intended reference, appropriate instruments and any necessary test loads specified for the supply. Do not treat a four-rail no-load reading as proof of loaded regulation.<\/p>\n<p>Record the connector cavity, reference cavity, sign and measured value for each rail. \u201cContinuity passed\u201d and \u201c+12 V present\u201d answer different questions. Neither establishes that an incompatible neighboring socket is physically blocked; keep that check visible as a third result.<\/p>\n<\/section>\n<section id=\"service-release\">\n<h2><span class=\"ez-toc-section\" id=\"Keep_the_approved_service_kit_aligned_with_production\"><\/span>Keep the approved service kit aligned with production<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>The released kit should identify the harness revision, both mating connector parts, keying variants, contact specification and assembly inspection record. If the harness can be sourced from two suppliers, compare the same interface evidence rather than accepting \u201cequivalent four-rail cable\u201d as a complete description.<\/p>\n<p>Reopen the review after a receiver-board revision, connector substitution, repinning, supply-suffix change or a new adjacent service port. A retained housing with a changed cavity assignment can defeat the original error-prevention design even though it still latches correctly.<\/p>\n<p>Use the worksheet to leave a traceable result for the technician and purchasing team. The useful release statement is specific: this harness revision, this Q-120B configuration and this receiver interface were checked against the attached records. It should not imply that every Q-120 family variant or future replacement is interchangeable.<\/p>\n<\/section>\n<section id=\"project-record\">\n<h2><span class=\"ez-toc-section\" id=\"Use_the_project_record\"><\/span>Use the project record<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p><a href=\"\/fa\/acceptance-record.html\/\">Open the blank Q-120B harness and unwanted-mating release record<\/a> to record your conditions, evidence and decisions. The worksheet contains no pre-approved result.<\/p>\n<\/section>\n<section class=\"cta\" id=\"project-review\">\n<p>When enquiring about the <a href=\"https:\/\/www.wehopower.com\/fa\/product\/ce-approved-120w-quad-output-switching-power-supply\/\">Q-120B four-output supply<\/a>, request the exact output and terminal information for the intended revision. Combine it with the receiver and connector documentation before releasing the service harness.<\/p>\n<\/section>\n<section class=\"sources\" id=\"sources\">\n<h2><span class=\"ez-toc-section\" id=\"Sources_and_further_reading\"><\/span>Sources and further reading<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<ol>\n<li><a href=\"https:\/\/www.wehopower.com\/fa\/product\/ce-approved-120w-quad-output-switching-power-supply\/\">WEHO Q-120 product variant table<\/a><\/li>\n<li><a href=\"https:\/\/www.wehopower.com\/wp-content\/uploads\/2021\/11\/Q-120.pdf\">WEHO Q-120 official specification sheet<\/a><\/li>\n<li><a href=\"https:\/\/supplychain.molex.com\/content\/molex\/molex-dot-com\/language-masters\/en\/trends-insights\/engineering-insights\/connector-mating.html\" target=\"_blank\" rel=\"noopener\">Molex Connector Fundamentals: Gender, Polarization, Keying and Coding<\/a><\/li>\n<\/ol>\n<\/section>\n<\/div>","protected":false},"excerpt":{"rendered":"<p>Four correct rail voltages can still reach the wrong receiver pins. Verify the Q-120B harness as a complete service interface, including orientation and unwanted mating paths.<\/p>","protected":false},"author":2,"featured_media":20350,"parent":0,"menu_order":76,"comment_status":"","ping_status":"","template":"","format":"standard","meta":{"_acf_changed":false,"_joinchat":[],"footnotes":""},"news_category":[284],"class_list":["post-20373","news","type-news","status-publish","format-standard","has-post-thumbnail","hentry","news_category-product-articles","entry"],"acf":[],"post_mailing_queue_ids":[],"_links":{"self":[{"href":"https:\/\/www.wehopower.com\/fa\/wp-json\/wp\/v2\/news\/20373","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.wehopower.com\/fa\/wp-json\/wp\/v2\/news"}],"about":[{"href":"https:\/\/www.wehopower.com\/fa\/wp-json\/wp\/v2\/types\/news"}],"author":[{"embeddable":true,"href":"https:\/\/www.wehopower.com\/fa\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.wehopower.com\/fa\/wp-json\/wp\/v2\/comments?post=20373"}],"version-history":[{"count":0,"href":"https:\/\/www.wehopower.com\/fa\/wp-json\/wp\/v2\/news\/20373\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.wehopower.com\/fa\/wp-json\/wp\/v2\/media\/20350"}],"wp:attachment":[{"href":"https:\/\/www.wehopower.com\/fa\/wp-json\/wp\/v2\/media?parent=20373"}],"wp:term":[{"taxonomy":"news_category","embeddable":true,"href":"https:\/\/www.wehopower.com\/fa\/wp-json\/wp\/v2\/news_category?post=20373"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}