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--></style></head><body lang=FR-CA link=blue vlink=purple style='word-wrap:break-word'><div class=WordSection1><p class=MsoNormal><span lang=EN-CA>There are wire links that set the correct AMERICA 120v voltages on the same PCB. These links are placed correctly.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-CA><o:p> </o:p></span></p><div><div style='border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0cm 0cm 0cm'><p class=MsoNormal><b><span lang=FR style='font-size:11.0pt;mso-ligatures:none;mso-fareast-language:FR-CA'>De :</span></b><span lang=FR style='font-size:11.0pt;mso-ligatures:none;mso-fareast-language:FR-CA'> Synth-diy <synth-diy-bounces@synth-diy.org> <b>De la part de</b> grant musictechnologiesgroup.com<br><b>Envoyé :</b> 19 février 2026 22:11<br><b>À :</b> synth-diy@synth-diy.org<br><b>Objet :</b> Re: [sdiy] Questioning on why both of this power transformer primary windings went almost short..<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal>I repaired a Garnet amp that blew its transformer when the generator it was hooked up to had been set for way too high a voltage (I don't remember what the customer said the voltage was, but they admitted the festival was smokier than originally planned). I think that was all that was wrong too. Aside from fuses. <br><br>GB<br><br>On 2/19/2026 5:20 PM, Jean-Pierre Desrochers via Synth-diy wrote:<span style='mso-ligatures:none;mso-fareast-language:FR-CA'><o:p></o:p></span></p></div><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><p class=MsoNormal><span lang=EN-CA>A customer brought me a guitar preamp that he said ‘blows its internal fuses..’</span><o:p></o:p></p><p class=MsoNormal><span lang=EN-CA>I checked the internals and found that both of the internal 315mA primary windings fuses were blown (F2 & F3).</span><o:p></o:p></p><p class=MsoNormal><span lang=EN-CA>The main 500mA fuse (F1) was ok.</span><o:p></o:p></p><p class=MsoNormal><span lang=EN-CA>So I connected my variac to <u>only one</u> of the primary windings (no fuses) to find that<br>reaching around 90VAC it started to drain around 1 AMP !</span><o:p></o:p></p><p class=MsoNormal><span lang=EN-CA>I checked the other primary winding alone and it behaved exactly the same,</span><o:p></o:p></p><p class=MsoNormal><span lang=EN-CA>1AMP at around 90VAC.</span><o:p></o:p></p><p class=MsoNormal><span lang=EN-CA>These measures were done with none of the secondaries connected (free wires).</span><o:p></o:p></p><p class=MsoNormal><span lang=EN-CA> </span><o:p></o:p></p><p class=MsoNormal><span lang=EN-CA>So my questioning is what the heck almost shorted each of these primary windings<br>exactly the same way..?</span><o:p></o:p></p><p class=MsoNormal><span lang=EN-CA>I connected external AC voltages to each of the secondaries bridge (one at the time)<br>and there were no shorts on each of them. The resulting DC voltages were as expected.</span><o:p></o:p></p><p class=MsoNormal><span lang=EN-CA>To create those shorts at each primaries it would have needed<br>that the 315mA fuses would have been replaced by much higher values<br>with some kind of shorts somewhere in the secondaries side.. ?</span><o:p></o:p></p><p class=MsoNormal><span lang=EN-CA>OR this is a manufacturing default that waited to awake ?</span><o:p></o:p></p><p class=MsoNormal><span lang=EN-CA>Anyway I ordered a new transformer replacement, but I don’t want<br>to fry it again because of something else that blew the first one..</span><o:p></o:p></p><p class=MsoNormal><span lang=EN-CA> </span><o:p></o:p></p><p class=MsoNormal><span lang=EN-CA>What do you think ?</span><o:p></o:p></p><p class=MsoNormal><span lang=EN-CA> </span><o:p></o:p></p><p class=MsoNormal><span lang=EN-CA> </span><o:p></o:p></p><p class=MsoNormal><span style='mso-ligatures:none'><img width=802 height=301 style='width:8.3541in;height:3.1354in' id="_x0000_i1025" src="x-moz-ews://grant%40musictechnologiesgroup.com@outlook.office365.com/Inbox/1217?header=quotebody&part=1.1.2&filename=image003.jpg"></span><o:p></o:p></p><p class=MsoNormal><span style='font-family:"Aptos",sans-serif;mso-ligatures:none;mso-fareast-language:FR-CA'><br><br><o:p></o:p></span></p><pre>________________________________________________________<o:p></o:p></pre><pre>This is the Synth-diy mailing list<o:p></o:p></pre><pre>Submit email to: <a href="mailto:Synth-diy@synth-diy.org">Synth-diy@synth-diy.org</a><o:p></o:p></pre><pre>View archive at: <a href="https://synth-diy.org/pipermail/synth-diy/">https://synth-diy.org/pipermail/synth-diy/</a><o:p></o:p></pre><pre>Check your settings at: <a href="https://synth-diy.org/mailman/listinfo/synth-diy">https://synth-diy.org/mailman/listinfo/synth-diy</a><o:p></o:p></pre><pre>Selling or trading? Use <a href="mailto:marketplace@synth-diy.org">marketplace@synth-diy.org</a><o:p></o:p></pre></blockquote><p class=MsoNormal><span style='font-family:"Aptos",sans-serif;mso-ligatures:none;mso-fareast-language:FR-CA'><o:p> </o:p></span></p></div></body></html>