<div dir="ltr">Make sure the tab on that LM7915 regulator has NO continuity to the heatsink and chassis. In my NS databook, the tab on the 79xx regulators is tied to the INPUT pin - not COMMON. Any second source suppliers will use the same pinout. This means you want NO electrical contact with the tab and plate/heatsink/chassis. The 79xx should have mica insulator between the tab and mounting plate (with thermal conductive paste), and non-conductive nylon washers on both the mounting screw head and nut, and nylon tube insulators on the screw shaft.<div><br></div><div>ps the pinout for 79xx regulators in the 1989 TI Linear Circuits Vol 3 databook is WRONG. Yes errors CAN appear in OEM databooks.<br><div><div><br></div><div>MC</div></div></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Sun, Jun 18, 2023 at 6:32 AM Adam (synthDIY) <<a href="mailto:synthdiy@adambaby.com">synthdiy@adambaby.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex"><div style="line-break:after-white-space"><br><div><br><blockquote type="cite"><div>On 18 Jun 2023, at 7:40 pm, Florian Anwander <<a href="mailto:fanwander@mnet-online.de" target="_blank">fanwander@mnet-online.de</a>> wrote:</div><br><div>
<div>
<div>PS: there is a picture of the PCB at
<a href="https://www.joness.com/gr300/pics/SPV-355/Roland_SPV-355_13.JPG" target="_blank">https://www.joness.com/gr300/pics/SPV-355/Roland_SPV-355_13.JPG</a>
but I could not find them (yet).<br></div></div></div></blockquote><div><br></div><div>Well at least that picture explains what Todd meant when he said "if the LM7915 is unplugged" - looks like the two regulators are on their own plugs, allowing a 'flying' attachment to some big heat sinks.</div><div>Whatever is holding those heat sinks on may have shorted I guess... and they look like they're almost touching</div><div><br></div><div>A</div><div><br></div><div><br></div><div><br></div><div><br></div><div><br></div><div><br></div><br><blockquote type="cite"><div><div><div>
<br>
Am 18.06.23 um 11:38 schrieb Florian Anwander:<br>
</div>
<blockquote type="cite">
<div>Though it is a shot in the mist:<br>
<br>
There are three types of tantalum capactors listed in the
service manual. I bet those are on the supply rails and I bet (a
little bit less) one of them got shorted.<br>
<br>
<span id="m_-6102076496608015261cid:part1.EbSffKYh.SfVf8F9m@mnet-online.de"><kiJb1bnXjLNtD1VZ.png></span><br>
<br>
<br>
Florian<br>
<br>
Am 16.06.23 um 19:12 schrieb Todd Sines via Synth-diy:<br>
</div>
<blockquote type="cite">
<span>I have an SPV-355 that was
behaving adequately fine until recently. Unit will power on,
(and LEDs illuminate correctly) if the -15V LM7915 is
unplugged, when engaged, it shorts and blows both fuses. </span><br>
<span></span><br>
<span>Wonder if anyone’s encountered
this and if so, what did you do, or where did you look first?</span><br>
<span></span><br>
<span></span><br>
<span>Todd</span> <br>
<fieldset></fieldset>
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